Half of men experience some degree of hair loss by the time they turn 50 and 40% of women are affected by age 70. “Pattern” hair loss is the most common cause of hair loss in both men and women.

Two medications are available to treat pattern hair loss: minoxidil (Rogaine) for men and women and finasteride (Propecia) for men. Unfortunately, neither of these medications is very effective, and both have side effects.

A number of integrative interventions including solubilized keratin, essential fatty acids, and saw palmetto extract may prevent hair loss and promote healthy hair growth.

Causes

• Hereditary and genetic factors: Influences age of onset, rate, and degree of hair loss
• Hormonal: Includes pregnancy, menopause, and hormonal disorders such as polycystic ovary syndrome and thyroid abnormalities
• Medical: Includes autoimmune diseases, skin conditions, and severe physical or emotional trauma
• Drug-induced: Includes chemotherapy and radiation therapy, beta-blockers, and oral contraceptives
• Nutritional: Severe protein and essential fatty acid deficiencies; overall malnutrition and crash diets; and iron, zinc, biotin, and vitamin D deficiencies

Treatment

• Finasteride, an oral medication approved for men, is a 5α-reductase inhibitor that suppresses the conversion of testosterone to dihydrotestosterone (DHT), which contributes to male pattern hair loss.
• Topical minoxidil is a vasodilator approved in both 2% and 5% formulations for treatment of pattern hair loss in men and women.
• Surgical hair restoration in the form of hair transplantation is widely used to treat pattern hair loss in men and women.
• Scalp cooling is an effective method of preventing hair loss induced by chemotherapy, reducing the risk by 62%.

Novel and Emerging Strategies

• While dutasteride, a medication like finasteride, has not been FDA approved as a treatment for hair loss, evidence indicates it effectively improves scalp hair growth, possibly even more than finasteride.
• Topical estrogens are available in Europe for use in hair disorders. In a trial in 53 women with female pattern hair loss, volunteers applied a topical 0.025% 17α-estradiol solution to their scalps daily for eight months. The treatment led to improvements in hair density, and was well tolerated during the study period.
• Early research indicates topical caffeine may exert positive effects on hair growth, including a stimulatory effect on hair follicles.

Integrative Interventions

• Solubilized keratin: In a placebo-controlled study in women with stressed or damaged hair, there was less hair loss, improved hair strength, and better hair appearance in the group taking Cynatine, a novel form of solubilized keratin.
• Essential fatty acids: A trial in women with early-stage hair loss found daily supplementation with fish oil, black currant seed oil (providing gamma-linolenic acid), lycopene, and vitamins C and E led to improved hair density compared with a control group.
• Silicon: In a study of women with fine hair who received orthosilicic acid (which provides silicon) or placebo for nine months, hair strength and elasticity were better preserved and hair thickness increased in the supplemented group.
• Saw palmetto: In a two-year trial comparing the effects of oral saw palmetto extract to finasteride in 100 men with mild-to-moderate pattern balding, finasteride led to hair regrowth in 68% of subjects, while 38% of those in the saw palmetto group experienced improved hair growth.
• Tocotrienols: In a study involving 38 women and men with various types and degrees of hair loss, those receiving supplements with alpha-tocopherol plus mixed tocotrienols experienced a more than 34% increase in hair numbers over eight months, while those receiving placebo experienced a slight decrease in hair numbers.

Half of men experience some degree of hair loss by the time they turn 50. Forty percent of women are affected by age 70 (Stough 2005; Levy 2013; Qi 2014; Hawit 2008).

“Pattern” hair loss is the most common cause of hair loss in both genders. In genetically susceptible individuals, the male hormone dihydrotestosterone, or DHT, contributes to pattern hair loss (Qi 2014; Santos 2015; Mayo Clinic 2015). An autoimmune condition called alopecia areata is another relatively common cause of hair loss, affecting about 2% of people at some point during their lives (Stough 2005; Levy 2013; Qi 2014; Hawit 2008). Other less common causes of hair loss include some medications, severe trauma or stress, and nutritional deficiencies.

Two medications are available to treat pattern hair loss: minoxidil (Rogaine) for men and women as an over-the-counter topical treatment, and finasteride (Propecia), an oral prescription drug for men that blocks the conversion of testosterone to DHT. Unfortunately, neither of these medications is remarkably effective, and both have side effects (Mayo Clinic 2015; Levy 2013).

Surgical hair restoration is an effective but expensive and invasive option for both men and women with long-term hair loss (Levy 2013; Stough 2005). For people undergoing chemotherapy—one of the most common medical causes of hair loss—scalp cooling can help maintain hair density (Shin 2015).

Intriguing new scientific findings are uncovering the next generation of therapies to combat hair loss. For instance, several trials have found that injecting platelet-rich plasma into the scalp can safely increase hair density (Ferneini 2016; Singh 2016). And the recent discovery that stem cells in hair follicles regulate hair growth has led to new avenues of research that may yield more promising treatments (Santos 2015).

In addition to a healthy diet (Lin 2016), a number of integrative interventions, including solubilized keratin (Beer 2014), essential fatty acids (Le Floc'h 2015), zinc (Karashima 2012), and saw palmetto extract (Murugusundram 2009; Rossi 2012) may prevent hair loss and promote healthy hair growth.

In this protocol, you will learn about different types of hair loss and their causes. Conventional as well as novel and emerging treatment strategies will be reviewed, and several integrative interventions that may help promote healthy hair growth will be examined.

An average person’s scalp contains 250,000‒500,000 hair follicles. Each follicle undergoes repeated cycles of three phases (Santos 2015):

• anagen, the growth phase, during which hair elongates;
• catagen, the regression phase, during which the follicle shrinks and detaches from its hair; and
• telogen, the resting phase.

On a healthy scalp, about 90–95% of hair follicles are in the anagen phase at any given time (Qi 2014; Santos 2015). Under normal circumstances, scalp hair shedding of 50‒150 hairs per day is matched by new hair growth at the same rate, so there is no net loss or gain (Fiuraskova 2003; Ahanogbe 2015).

Cells at the base of the hair follicle, in a region called the dermal papilla, are responsible for initiating and regulating the hair follicle cycle (Driskell 2011). These dermal papilla cells are regulated by hormones, growth factors, and inflammatory cytokines (Santos 2015; Inui 2013).

Types of Hair Loss

Androgenetic alopecia, also called male and female “pattern” hair loss, is the most common type of alopecia in men and women. Male pattern hair loss typically causes thinning and recession along the front hairline and temples, as well as the crown of the head. Female pattern hair loss usually causes thinning at the crown of the head (Qi 2014).

Male pattern hair loss is triggered mainly by the effects of the androgen (male hormone) dihydrotestosterone (DHT) on the dermal papilla cells of the hair follicle. DHT is made from testosterone by the enzyme 5-alpha reductase. DHT shortens the anagen phase in genetically predisposed hair follicles, resulting in smaller and shorter hairs (Fiuraskova 2003; Qi 2014). Female pattern baldness may involve a follicular sensitivity to DHT (Herskovitz 2013); however, the drop in estrogen after menopause may also contribute to changes in hair follicles that result in increased hair loss (Levy 2013).

Other types of alopecia include (Qi 2014; Hawit 2008; Mayo Clinic 2015):

• Alopecia areata. Alopecia areata, an autoimmune condition in which the immune system attacks hair follicles, can affect children and adults of both genders. It causes round patches of balding, mostly on the scalp and beard region.
• Telogen effluvium. Telogen effluvium is a condition in which 20–50% of scalp hair follicles abnormally transition into the telogen (resting) phase and shed their hair. Telogen effluvium is often triggered by physical or psychological stress, or illness. More women than men have telogen effluvium.
• Anagen effluvium. Anagen effluvium is a condition in which the shafts of hairs in the anagen (growth) phase are weakened and break. It is most commonly triggered by radiation therapy and cancer chemotherapy, but may also be related to heavy metal toxicity or exposure to other poisons (Harrison 2009).
• Cicatricial (scarring) alopecias. Hair loss that involves scarring is usually related to an underlying condition or disease. Chronic pressure to the scalp from certain hairstyles can result in traction alopecia, while application of chemicals can also cause long-term inflammation and scarring. Unlike other types of hair loss, cicatricial alopecias are often permanent.

Medical Conditions Associated with Hair Loss

Cardiovascular disease and metabolic syndrome. Androgenetic alopecia may be an indicator of cardiovascular risk. In one study, 80 men and 70 women with early-onset androgenetic alopecia had significantly higher triglyceride as well as total and LDL-cholesterol levels, and lower HDL cholesterol, than men and women without hair loss (Arias-Santiago 2010). In another study, male androgenetic alopecia was correlated with high blood pressure (Ahouansou 2007).

Early onset of pattern hair loss may be a stronger predictor of cardiovascular disease than later-onset androgenetic alopecia. In one study, men with early-onset androgenetic alopecia were more than three times as likely to need coronary artery bypass surgery before age 60 than men with later-onset hair loss and those without hair loss (Matilainen 2001). In addition, early-onset androgenetic hair loss has been linked to an increased risk of metabolic syndrome in men (Banger 2015; Gopinath 2016), while female pattern hair loss has been associated with metabolic syndrome in women (Herskovitz 2013).

Prostate conditions. Research has not consistently found a connection between androgenetic alopecia and benign prostate enlargement, even though both are related to high levels of DHT (Arias-Santiago 2012; Dastgheib 2015; Qi 2014; Carson 2003). However, a review of studies concluded male pattern hair loss occurring at the crown of the head was associated with a 25% increase in prostate cancer risk (Amoretti 2013). Additional evidence found a 56% increase in prostate cancer deaths in men with any balding and an 83% increase in men with moderate balding, pointing to a relationship between male pattern hair loss and fatal prostate cancer (Zhou 2016). Further evidence for this connection is found in research showing that use of finasteride, a 5-alpha reductase inhibitor that reduces serum DHT levels, is associated with reduced overall prostate cancer risk (Wilt 2008; Chau 2015); although it may be less effective at preventing high-grade than low-grade prostate cancers (Hoque 2015).

Because some evidence suggest androgenetic alopecia may correlate with increased prostate cancer risk, men experiencing male pattern hair loss, especially those whose hair loss began at an early age, should monitor their prostate health and take steps to prevent prostate cancer. More information about keeping your prostate healthy is available in the Prostate Cancer Prevention protocol.

Risk of hair loss increases with age and is higher in those with a family history of hair loss (Gokce 2022). Aging and genetics overlap with environmental exposures, dietary and lifestyle factors, stress, and hormonal changes to influence the risk of hair loss (Kinoshita-Ise 2023). Men have a higher risk of androgenetic alopecia, the most common type of hair loss (Gokce 2022; Oiwoh 2024).

Hair loss is a multifactorial condition that can involve genetic, hormonal, inflammatory, metabolic, medical, drug-related, and nutritional causes.

Genetic Causes

Genetics have an important influence on age of onset, rate, and degree of hair loss in male and female androgenetic alopecia. The androgen receptor gene helps determine the response of hair follicles to androgens, and variants of this gene have been identified as important contributors to androgenetic alopecia risk. Multiple other genes also appear to be involved (Gokce 2022; Oiwoh 2024).

Hormonal Causes

In women, hair loss is more common at times of hormonal changes such as pregnancy, childbirth, and menopause (Ebrahimzadeh-Ardakani 2021; Owecka 2024). Other hormonal causes of hair loss include polycystic ovary syndrome (PCOS), hyperthyroidism and hypothyroidism, high insulin levels, and high cortisol levels.

Androgens

Dihydrotestosterone (DHT), produced from testosterone by the action of the enzyme 5-alpha-reductase, is a more potent stimulator of androgen receptors than testosterone. Excess production of DHT in hair follicles of men and women alters the hair cycle, increasing hair thinning and loss (Owecka 2024).

Estrogen

The drop in estrogen production that occurs during the menopausal transition is thought to play a major role in female pattern hair loss (Kamp 2022). Testosterone’s influence increases after menopause due to a shift in its activity relative to estrogen (Hirschberg 2023). In addition, estrogen is a key regulator of the hair cycle, and estrogen deficiency may disrupt normal hair growth (Kamp 2022; Owecka 2024).

Insulin Resistance

Multiple observational studies have linked early-onset androgenetic alopecia with metabolic disturbances, including insulin resistance/high insulin levels, obesity, and metabolic syndrome, in men and women (Qiu 2022; Sodagar 2023; Liu 2024). Insulin resistance has also been implicated as a biomarker for alopecia areata: a study that compared 52 alopecia areata patients with 17 healthy individuals found higher insulin levels were correlated with the condition (Waskiel-Burnat 2022).

Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a hormonal and metabolic condition that affects about 5–10% of women. Its two predominant features are insulin resistance and high levels of androgens (male hormones, including testosterone, DHT, and dehydroepiandrosterone [DHEA]). These hormonal disturbances can lead to abnormal hair patterns such as androgenetic alopecia as well as increased facial hair (hirsutism) (Cussen 2022; Jiang 2022).

Thyroid Disorders

Thyroid hormones are needed for normal hair follicle growth and maintenance. Thyroid disorders, including hypothyroidism, hyperthyroidism, and autoimmune thyroid diseases, have been associated with androgenetic alopecia, alopecia areata, and telogen effluvium (Hussein 2023; Owecka 2024). About 33% of patients with hypothyroidism and 50% of those with hyperthyroidism have been reported to have hair loss (Hussein 2023). Hypothyroidism slows down hair growth, whereas hyperthyroidism is thought to trigger hair loss via free radical damage (Hussein 2023; Owecka 2024).

Cortisol

Cortisol is the body’s main stress hormone. Excess cortisol production, such as due to intense stress or Cushing’s syndrome, may promote hair loss by inhibiting production and stimulating breakdown of structural molecules in skin that affect hair follicle integrity and function (Savas 2022; Owecka 2024).

Inflammation & Oxidative Stress

While profound immune dysfunction and inflammation play a primary role in alopecia areata and scarring (cicatricial) alopecias, micro-inflammation has been implicated in gradual changes to hair follicle function that contribute to androgenetic alopecia (Cuevas-Diaz Duran 2024; Oiwoh 2024). Micro-inflammation may be caused by local microbes, sun exposure, smoking, and exposures to other toxins or pollutants (Cuevas-Diaz Duran 2024).

Chronic inflammation generates free radicals and raises oxidative stress. Excess oxidative stress can impair dermal papilla cells and has been linked to hair aging, characterized by hair graying and loss. Lipid peroxides and reduced antioxidant activity can also increase oxidative stress and contribute to hair loss (Liang 2023; Du 2024).

Obesity

Obesity is associated with inflammation, oxidative stress, insulin resistance, and hormonal imbalances, which can damage hair follicle stem cells and drive hair loss (Morinaga 2021; Smolarczyk 2024). In observational research, obesity (especially abdominal obesity) and other components of metabolic syndrome have been associated with early-onset and more severe androgenetic alopecia (Hirsso 2007; Yang 2014; Vora 2019; Oiwoh 2023).

Other Health Conditions

Several medical conditions can cause hair loss:

• Some autoimmune diseases (Kinoshita-Ise 2023)
• Dermatologic diseases such as tinea capitis, psoriasis, seborrhea, and atopic dermatitis (Trueb 2018; Kinoshita-Ise 2023)
• Trichotillomania (a psychological disorder characterized by hair pulling) (Kinoshita-Ise 2023)
• Liver or kidney failure (Kinoshita-Ise 2023)
• Acute and chronic infections, such as some severe respiratory infections, Dengue fever, and human immunodeficiency virus (HIV) (Kinoshita-Ise 2023)
• Severe physical or emotional stress or trauma (Kinoshita-Ise 2023)
• Toxic exposures to heavy metals, pesticides such as boric acid, and polyaromatic hydrocarbons (Samra 2024)
• Cardiovascular risk factors such as hypertension or low high-density lipoprotein (HDL) cholesterol levels (Vora 2019)

Certain Medications

Many different medications have been reported to cause cases of hair loss, but few regularly cause this side effect. Telogen effluvium and anagen effluvium are the most common forms of drug-induced hair loss and typically resolve within three to six months of stopping the drug. In rare instances, medications have been reported to trigger alopecia areata or irreversible scarring alopecia (Alhanshali 2023).

A wide array of anti-cancer chemotherapy drugs cause hair loss (Dunnill 2018; Sachse 2024). Radiation therapy is another frequent cause of hair loss in cancer patients (Lin 2023). Some other drug categories that may cause or worsen hair loss include:

• Psychiatric medications (including antidepressants, antipsychotics, mood stabilizers, and amphetamines) (Meaux 2021; Alhanshali 2023)
• Antibiotic, antifungal, and antiviral medications (Alhanshali 2023)
• Anti-seizure medications (Alhanshali 2023)
• Osteoporosis medications (Alhanshali 2023)
• Proton pump inhibitors (Alhanshali 2023)
• Anti-diabetes medications (Alhanshali 2023)
• Hormonal contraceptives (Williams 2021)
• Anticoagulants (Marques 2020)
• Beta-blockers (Tatu 2019)

Nutritional Causes

Overall malnutrition, such as due to intense dieting, eating disorders, or bariatric surgery, is a known cause of hair loss (Trüeb 2020; Klein 2021; Smolarczyk 2024). In addition, deficiencies of individual macro- and micronutrients absent of other causes can contribute to some types of hair loss:

• Iron deficiency anemia is a cause of hair loss. A low ferritin level in the absence of anemia is another indicator of poor iron status that may be a factor in hair loss, especially telogen effluvium (Almohanna 2019; Zhang 2023).
• Zinc is involved in hair follicle function and levels have been found to be lower in people with androgenetic alopecia, alopecia areata, and telogen effluvium than healthy subjects in observational research (Guo 2017; Zou 2022).
• Vitamin D deficiency has been found to be more common in individuals with various types of hair loss (Zaaroura 2023; Chen 2024).
• Severe protein deficiency can result in hair loss, although this is extremely rare in developed countries (Guo 2017).
• Inadequate intake of the essential fatty acids linoleic acid and alpha-linolenic acid may contribute to hair loss by influencing androgen production (Guo 2017). In addition, essential fatty acid deficiency is a cause of physiologic stress that may trigger telogen effluvium (Asghar 2020).

A systematic review and meta-analysis published in 2024 examined 34 studies involving 4,931 participants from 16 countries to evaluate the relationship between serum trace elements and alopecia areata. It found that individuals with alopecia areata had significantly lower levels of serum vitamin D and zinc compared to healthy controls. Vitamin D deficiency was strongly associated with a higher risk of alopecia areata, with a pooled odds ratio of 2.48, meaning those with low vitamin D levels were over twice as likely to develop alopecia areata. Low zinc levels were also linked to alopecia areata, while no consistent relationship was observed with copper levels. The findings suggest that vitamin D and zinc deficiencies might contribute to the development of alopecia areata, although high variability among studies limits the strength of these conclusions. Future research should explore causal relationships and the potential of vitamin D and zinc supplementation as treatments for alopecia areata (Wu 2024).

Unhealthy Scalp- and Hair-Care Practices

Unhealthy scalp- and hair-care practices can contribute to hair loss. The following practices may help prevent unnecessary hair damage and loss (Rucker Wright 2011; American Academy of Dermatology Association 2024):

• Avoid tight hairstyles that put pressure on the scalp, such as tight braids, buns, and ponytails.
• Avoid twisting, rubbing, and pulling on hair, and comb hair gently with a wide-toothed comb.
• Avoid harsh hair treatments like hot rollers, curling irons, hot oil treatments, and permanents.

Several lab tests may provide useful information when investigating the cause of hair loss:

Complete Blood Count (CBC) and Chemistry Panel

A CBC/chemistry panel can reveal some medical conditions that may contribute to hair loss.

Ferritin

Even in the absence of anemia, a low ferritin level is an indicator of iron deficiency, which may contribute to hair loss (Zhang 2023). It is important to bear in mind that ferritin levels can rise, masking iron deficiency, in inflammatory, infectious, neoplastic, and liver conditions (Almohanna 2019).

Thyroid Panel

Thyroid disorders may cause hair loss, especially in women (Owecka 2024). Hair loss is observed in approximately 50% of people with hyperthyroidism and 33% with hypothyroidism (Hussein 2023). Thyroid stimulating hormone (TSH), free T3, free T4, and reverse-T3 levels may be helpful in identifying thyroid disease.

Sex Hormone Panel

Sex hormone imbalance is a major contributing factor in androgenetic hair loss (Hirschberg 2023). Estradiol (the most active estrogen), DHEA-sulfate, free and total testosterone, and DHT levels are components of a comprehensive hormone balance assessment.

High Sensitivity C-reactive Protein (hs-CRP)

Alopecia areata is associated with higher hs-CRP levels (Gao 2022).

Other Testing

Blood testing to assess the fatty acid profile, such as the Omega-3 Index, can provide information about fatty acid balance. Other tests that may be useful as part of a comprehensive evaluation include 25-hydroxy vitamin D, hemoglobin A1c, insulin, and cortisol levels.

Androgenetic Alopecia Treatment

Two drugs, oral finasteride and topical minoxidil, are approved by the US Food and Drug Administration (FDA) for the treatment of androgenetic alopecia in men (Bajoria 2023; Gupta 2024). Finasteride is a medication that inhibits 5-alpha reductase, blocking the conversion of testosterone to DHT (AHLA 2010; Qi 2014). Minoxidil is thought to work by dilating blood vessels, thus increasing blood flow to hair follicles, as well as by reducing inflammatory signaling and directly promoting hair growth (Kaiser 2023). Minoxidil is also approved for use in treating androgenetic alopecia in women (Gupta 2024). Unfortunately, these medications have poor response rates (Kaiser 2023). They are frequently used together or combined with other therapies to increase their effectiveness and minimize potential adverse events (Bajoria 2023; Gupta 2024).

While oral finasteride has a higher rate of efficacy than minoxidil, its adverse side effect profile can affect patient adherence and is an important consideration. Mild side effects include low blood pressure and dizziness, but its more alarming side effects include muscle atrophy, male breast growth (gynecomastia), and depression and sexual dysfunction that may persist after stopping therapy. Some research further suggests it may harm male fertility (Nestor 2021; Kaiser 2023).

Topical minoxidil frequently causes hair growth in unwanted locations on the body and can also cause headaches, short-term hair shedding at the beginning of therapy, and inflammation, itching, and scaling of the scalp (Kaiser 2023). A large number of patients who initiate treatment with minoxidil discontinue therapy, and side effects are a contributing factor in more than half of these cases (Shadi 2023).

Unfortunately, these medications are only effective during active use, so they must be used continuously and indefinitely (Nestor 2021; Shadi 2023).

Surgical Hair Restoration Techniques

Surgical hair restoration in the form of hair transplantation is widely used to treat pattern hair loss in men and women (True 2021). It involves extraction of hair follicles from a donor site (often the back of the head) and transplanting them in the area of hair loss (usually the crown and/or frontal areas of the head) (Liu 2024). Hair follicles from the back of the head tend to be less sensitive to the effects of androgens, even when moved to areas of the scalp that have experienced pattern hair loss (Cuevas-Diaz Duran 2024).

There are two techniques currently used for harvesting hair follicles: follicular unit transplantation and follicular unit extraction.

Follicular unit transplantation (FUT, also known as strip surgery) involves removing a linear strip of skin from the back of the scalp and stitching the resulting wound. The strip is then carefully separated into follicle unit bundles (Othman 2023), which are naturally occurring clusters of one to four hair follicles along with their supportive oil glands, muscles, and connective tissues (ISHRS 2024). These follicular units are then grafted onto areas of the scalp where hair loss has occurred. The advantages of FUT include not requiring scalp shaving, a shorter surgery time, and the ability to harvest a large number of follicular units in one session (Othman 2023). However, strip surgery can produce a linear scar that may become hypertrophic (enlarged) or be visible (Liu 2024).Furthermore, damage to hair follicles near the incision site can make follow-up transplant sessions, if needed, more challenging (Othman 2023).

Follicular unit extraction (FUE)—the newer and more commonly used of the two techniques—involves shaving a region on the back of the scalp, identifying a number of follicular units over a wide area, and extracting them individually using a circular blade or other biopsy tool. The hair follicles are then transplanted in the region affected by hair loss (Othman 2023). FUE can take hours and possibly multiple sessions, but usually leaves little scarring and results in a more natural-looking distribution of hair where follicular units were extracted. In addition, some evidence suggests FUE results in better follicle viability and higher rates of graft survival. In those with sparse scalp hair, FUE may be performed using hair from other body regions, such as the beard or chest (Othman 2023).

It is important to note that hair transplantation surgery is not appropriate in every case of hair loss. For example, it is generally not recommended for patients with diffuse unpatterned hair loss, scarring alopecia, substantial active hair loss, or certain psychiatric or medical conditions. The best results occur in patients with good general health, scalp health, and hair quality in the donor area, and who have reasonable expectations (True 2021).

Light Therapy

Light therapy, also referred to as photobiomodulation, is frequently used to promote hair growth in patients with androgenetic alopecia and other types of hair loss. It involves the use of an external light-emitting device, such as a specialized comb, hat, or helmet, that exposes the scalp to low-level laser-sourced or light-emitting diode (LED)-sourced light at wavelengths corresponding to red, near-infrared light, and infrared light (Hamblin 2019; Devjani 2023).

Evidence suggests photobiomodulation may upregulate cellular growth factors, increase blood flow, and support hair follicle cell proliferation, leading to hair regrowth (Cho 2023; Devjani 2023). Furthermore, a laboratory study using hair follicles showed exposure to red light altered gene expression and slowed the transition from anagen to catagen in the hair cycle (Yang 2021).

Clinical trials have shown low-level laser therapy using red, near-infrared, or infrared light (“red-light therapy”) is an effective treatment for androgenetic alopecia (Glass 2021; Zhang 2022). A meta-analysis of 15 controlled clinical trials involving a total of 795 subjects with androgenetic alopecia found low-level laser therapy, alone or combined with red light therapy, increased hair density (Gupta 2021). Another meta-analysis that included 15 randomized controlled trials involving a total of 1,172 participants showed photobiomodulation using low-level laser therapy increased the effectiveness of minoxidil in men and women with androgenetic alopecia compared with minoxidil alone (Zhou 2020). Systematic reviews of clinical trials using low-level laser therapy concluded longer sessions, less frequent sessions (eg, three times weekly instead of daily), and the use of pulsed (versus continuous) irradiation were associated with increased effectiveness of this type of photobiomodulation (Liu 2019; Gupta 2020).

Photobiomodulation is relatively safe but can occasionally cause tenderness, itching, or other abnormal sensations on the scalp (Devjani 2023). Numerous devices such as combs and ball caps containing light-emitting diodes (LEDs) are readily available in the market.

Alopecia Areata Treatment

There is no cure for alopecia areata, and evidence for the effectiveness of most existing treatments is limited. Newer drugs known as JAK inhibitors are an exception, having demonstrated efficacy and safety in multiple randomized controlled trials in patients with severe alopecia areata (Egeberg 2023; Malhotra 2023; Mateos-Haro 2023).

Psychological Support

Hair is an important aspect of self-image, and excess hair loss can be emotionally distressing. Patients with severe alopecia areata have reported experiencing diminished quality of life, substantial emotional and mood symptoms, decreased self-esteem, and challenges in everyday activities (Bewley 2024). Because of this, as well as the uncertainty of its course and treatment, psychological support is an important component of alopecia areata management.

Various types of psychological interventions have been studied in patients with alopecia areata. Mindfulness-based stress reduction, hypnotherapy, and other psychotherapies have been found to reduce emotional symptoms like anxiety and distress and improve quality of life scores in alopecia areata patients. Some evidence suggests psychological interventions may also increase the effectiveness of drug treatment, improve scalp blood flow, and have a small positive impact on hair regrowth (Maloh 2023).

Local and Topical Therapies

Corticosteroids. Topical or locally injected corticosteroids are first-line therapy when there is patchy hair loss or less than 50% of the scalp is involved. Approximately 60–70% hair regrowth has been reported in patients with mild-to-moderate alopecia areata treated with corticosteroid therapy, and maintenance therapy is sometimes needed. However, topical and local corticosteroids are neither feasible nor effective in severe, extensive, or rapidly progressing cases. Side effects of topical treatment are generally minor; however, repeated or high-dose corticosteroid use can cause temporary or long-term skin atrophy (Malhotra 2023).

Contact immunotherapy. In patients with extensive hair loss, contact (topical) immunotherapy has been a common treatment. This therapy involves the topical use of irritant chemicals like dinitrochlorobenzene, diphenylcyclopropenone or squaric acid dibutyl ester to induce contact dermatitis, which is theorized to modulate immune cell activity. Due to adverse effects, diphenylcyclopropenone is the most commonly used agent (Malhotra 2023).

Although no placebo-controlled trials have been published (Egeberg 2023), a meta-analysis of findings from 45 clinical trials and observational studies found 65.5% of alopecia areata patients treated with contact immunotherapy experienced some hair regrowth and 32.3% had complete hair regrowth (Lee 2018). Adverse side effects are common and can include lymph node swelling and persistent dermatitis of the face and neck with itching, blistering, eczema, and hives (Egeberg 2023). Diphenylcyclopropenone can also cause systemic side effect such as fever and joint pain (Malhotra 2023).

Anthralin. Topical anthralin, a synthetic, tarry psoriasis medication, is another irritant agent. It is considered a second-line treatment for alopecia areata and is most often used in conjunction with diphenylcyclopropenone, despite a lack of consistent evidence for its advantages (Egeberg 2023). Although its mechanism of action is uncertain, it is thought to modulate immune activity and reduce inflammation (Malhotra 2023). Anthralin has been reported to be helpful in pediatric alopecia areata patients, but it does not appear to be as effective as topical corticosteroids, contact immunotherapy, or light therapy (Barton 2022; Behrangi 2022; Zafrir 2023). It can cause side effects such as itching, redness, scaling, and brown staining of the skin. Anthralin also stains clothing and hair (Malhotra 2023).

Light therapy. Light therapy, or photobiomodulation, is sometimes used to treat alopecia areata. Case reports and clinical trials have indicated light in the red, near-infrared, and infrared wavelengths can increase hair density in patients with this condition (Tan 2020; Zhang 2022; Palma 2023; Pixley 2023). One systematic review suggested that light therapy in combination with topical minoxidil may be effective. However, the authors noted that the quality of the evidence was not high and that more research was needed (Zhang 2023). Overall, photobiomodulation therapies, including UV and infrared light, as well as the 308-nm excimer laser (a device used in light therapy), have demonstrated some efficacy in treating alopecia areata. These therapies may be viable options, especially for people who have not responded to conventional treatments.

Systemic Therapies

JAK inhibitors. The FDA approved the JAK inhibitors baricitinib (Olumiant) and ritlecitinib (Litfulo) for treating severe alopecia areata in 2022 and 2023, respectively. Tofacitinib (Xeljanz) is an oral medication first approved by the FDA for the treatment of rheumatic arthritis that is also used off-label to treat alopecia areata. These oral medications inhibit enzymes known as Janus kinases (JAK) 1 and 2. JAK enzymes are involved in signaling pathways related to inflammation. JAK inhibitors are used for a range of inflammatory, autoimmune, and blood disorders, including rheumatoid arthritis, atopic dermatitis, and psoriasis (Ali 2022). Other JAK inhibitors that have shown benefits in placebo-controlled trials in alopecia areata patients include deuruxolitinib (Leqselvi, approved by the FDA in 2024) and brepocitinib (King 2021; Egeberg 2023; David 2024).

Multiple randomized controlled trials and meta-analyses have shown JAK inhibitors, particularly baricitinib, can effectively promote hair growth in subjects with alopecia areata (Barati Sedeh 2023; Ko 2023; Wei 2023). One meta-analysis of findings from three randomized placebo-controlled trials involving a total of 1,282 participants with severe alopecia areata found the proportion of patients who achieved hair coverage over at least 80% of the scalp was more than six times higher with baricitinib than placebo (Mahmoud 2023).

JAK inhibitors have a higher safety profile than many other alopecia areata treatment options (Guan 2024). Nevertheless, they can cause a range of adverse effects, including increased infections, acne, lab value abnormalities (increased serum creatine phosphokinase and liver enzyme levels, indicators of muscle and liver damage, respectively), headaches, and nausea (Egeberg 2023).

Systemic corticosteroids. Corticosteroid drugs like betamethasone (Celestone) and prednisolone (Orapred) have immune-suppressing and anti-inflammatory effects (Williams 2018). Oral, intramuscular, and intravenous corticosteroids are sometimes used to control severe alopecia areata. Treatment is often administered in high-dose pulses, such as for two to three days every two to three weeks. Clinical trials indicate pulsed corticosteroid therapy can induce hair regrowth, but efficacy diminishes as severity increases. In addition, relapse and adverse side effects (eg, acne, weight gain, digestive upset, muscle pain, loss of menstrual periods, skin damage, and fluid retention) are common (Egeberg 2023; Rastaghi 2023).

Methotrexate. Methotrexate (Trexall, among others) is an immunosuppressant and chemotherapy agent used to treat autoimmune diseases and some cancers (NLM 2017). Observational studies and several randomized controlled trials have indicated methotrexate can have a modest positive effect on alopecia areata. It is mainly used in combination with systemic corticosteroids (Phan 2019). A randomized clinical trial published in 2023 compared methotrexate alone to methotrexate combined with low-dose prednisone in adults with severe alopecia areata totalis (complete hair loss of the scalp) or universalis (alopecia affecting the entire body) that persisted despite prior treatments. Participants initially received methotrexate (25 mg weekly) or placebo for six months, with non-responders rerandomized to add prednisone (20 mg/day for three months, then 15 mg/day) or placebo for the subsequent six months. The primary outcome was complete or nearly complete hair regrowth at 12 months. Methotrexate combined with prednisone achieved complete regrowth in 20– 31% of patients, significantly outperforming methotrexate alone or placebo. Side effects were mild, and the combination therapy showed promise as an effective, cost-efficient treatment for alopecia areata (Joly 2023). ​Nevertheless, relapse rates are high and adverse side effects may include digestive upset, low white blood cell count, and elevated liver enzyme levels (Egeberg 2023).

Azathioprine. Small uncontrolled studies suggest azathioprine (Imuran), another immunosuppressant drug, may stimulate hair regrowth in some patients with moderate-to-severe alopecia areata, with potential lasting improvement (Egeberg 2023; Malhotra 2023). Azathioprine is particularly considered when patients require a steroid-sparing agent due to the long-term side effects of corticosteroids. Like other immunosuppressants, it can cause serious adverse side effects including bone marrow suppression, pancreatitis, increased liver enzyme levels, and diarrhea (Egeberg 2023). Of note, a double-blind, randomized, controlled trial conducted in Pakistan and published in 2024 comparing azathioprine to tofacitinib (a JAK inhibitor) found that tofacitinib was significantly more effective, with a greater improvement in the Severity of Alopecia Tool (SALT) score at six months. This trial suggests that while azathioprine is effective, newer treatments like tofacitinib may offer superior efficacy (Paracha 2024).

Sulfasalazine. Sulfasalazine (Azulfidine) is a drug with immune-modulating, anti-inflammatory, and immunosuppressant actions. It is used to treat autoimmune diseases such as ulcerative colitis and rheumatoid arthritis. Uncontrolled trials using sulfasalazine in alopecia areata patients have shown a relatively low rate of response with a potentially substantial relapse rate (Mushtaq 2020). Sulfasalazine use is associated with a range of side effects, including digestive upset, headaches, dizziness, rash, hair thinning, and skin pigmentation, as well as low white blood cell count and elevated liver enzyme levels (Mushtaq 2020). New drugs like the JAK inhibitors are likely more effective than sulfasalazine.

Telogen Effluvium Treatment

Telogen effluvium is marked by sudden excessive hair loss, usually triggered by a major physical or psychological stressor such as high fever, infection, childbirth, major surgery, emotional distress, chronic disease, or medications (Chien Yin 2021; Kinoshita-Ise 2023). Hair regrowth typically occurs within four to six months of the inciting event, but chronic telogen effluvium can occur in cases of repetitive or chronic stress or for unknown reasons. In chronic cases, topical minoxidil or corticosteroids may be recommended, but there is no definitive therapy for chronic telogen effluvium (Asghar 2020; Kinoshita-Ise 2023). Some experts suggest iron supplementation may be helpful for those with inadequate levels of ferritin, but the evidence upon which this theory is based is limited (Bergfeld 2023).

Scalp Cooling

Observational and clinical studies have indicated scalp cooling can effectively reduce chemotherapy-induced hair loss (Bajpai 2020; Lugtenberg 2022; Brook 2024; Kang 2024). One meta-analysis of 31 studies found more than 60% of cancer patients treated with taxanes (a class of chemotherapeutics associated with high rates of hair loss) achieved <50% hair loss by using scalp cooling during treatment (Lambert 2024). Scalp cooling involves wearing a continuously cooled cap from 30 minutes before until as long as 180 minutes after chemotherapy treatment. It is believed to prevent hair loss by reducing the amount of chemotherapeutic drug reaching hair follicles and lowering the rate of biochemical activity within hair follicles (Wikramanayake 2023).

Novel and Off-Label Medications

Low-Dose Oral Minoxidil

Emerging research suggests an oral form of minoxidil may be as effective as the widely used topical form. A randomized controlled trial in men with androgenetic alopecia found 5 mg of oral minoxidil per day was as effective at increasing hair density after 24 weeks as 1 mL of 5% topical minoxidil applied twice daily. The most common adverse effects included excess hair growth in other body regions and headache (Penha 2024). Oral (1 mg daily) and topical (5%) minoxidil were also found to be similarly effective in an open clinical trial in 52 women with female pattern hair loss (Ramos 2020). Other clinical trials have indicated oral minoxidil can increase hair density in men and women with androgenetic alopecia (Panchaprateep 2020; Vastarella 2020).

A review of 17 clinical trials concluded oral minoxidil was a relatively safe and effective option for individuals with various types of hair loss who have difficulty with topical treatment (Randolph 2021). Potential serious adverse effects include rapid or abnormal heart rhythms, low blood pressure, pericardial effusion, and leg edema (Devjani 2023).

Topical Finasteride

Finasteride, a 5-alpha reductase inhibitor, is only approved as an oral drug in the United States to treat androgenetic alopecia and benign prostatic enlargement; however, a topical preparation being used in some European countries and South Korea is currently under investigation (Gupta 2024). Some compounding pharmacies may have topical finasteride and minoxidil combination formulations available within the United States, although these products are not FDA approved. Early findings suggest topical finasteride is as effective as oral finasteride—and may have a more favorable side effect profile. A randomized controlled trial in 323 men with androgenetic alopecia found that 24 weeks of treatment with topical 0.25% finasteride spray increased target area hair counts more than placebo and similarly to oral finasteride, yet maximum circulating levels of the drug were more than 100-fold lower with topical than oral finasteride (Piraccini 2022). Other clinical trials in men with androgenetic alopecia show topical treatment with 0.25% finasteride plus 5% minoxidil was more effective than either drug alone for improving hair counts after six months (Bharadwaj 2023; Rossi 2024). In an observational study involving 119 postmenopausal women with female pattern hair loss using 2% topical minoxidil, adding 0.5% topical finasteride to therapy improved subjective assessment of female patter hair loss more than adding 0.05% topical estradiol (Rossi 2020). Topical finasteride can sometimes cause scalp irritation, burning, itching, and redness (Devjani 2023).

Dutasteride

Like finasteride, dutasteride (Avodart) is a 5-alpha reductase inhibitor used to treat benign prostate enlargement; but as of 2024, it is not FDA approved for the treatment of alopecia. However, there are two forms, or isoenzymes, of 5-alpha reductase, and while finasteride inhibits one isoenzyme, dutasteride inhibits both. Dutasteride has not been approved by the FDA as a treatment for hair loss, but considerable evidence indicates it effectively improves scalp hair growth, possibly more effectively than finasteride (Shanshanwal 2017; Bajoria 2023; Gupta 2024).

Prostaglandin Analogs

Latanoprost (Xalatan) and bimatoprost (Latisse) are prostaglandin analogs that have been studied for their effect on hair loss. They work by stimulating the hair cycle and lengthening the anagen phase (Zeppieri 2024). Bimatoprost is FDA approved to promote eyelash growth, and both drugs have shown promise in treating hair loss, including due to androgenetic alopecia and alopecia areata (Yazdanian 2021; Jiang 2023). Reported side effects have included upper respiratory infections, other infections, increased body hair, and skin irritation with itching, burning, and redness (Jiang 2023).

Topical Retinoids

Vitamin A plays an important and complex role in hair follicle function, and both deficiency and excess can trigger hair loss (VanBuren 2022). A topical solution made with the vitamin A derivative tretinoin (Retin-A) and minoxidil may improve minoxidil’s efficacy (Sharma 2019). In one randomized comparison trial, topical treatment with 5% minoxidil plus 0.01% tretinoin once daily was as effective in promoting hair growth as conventional 5% minoxidil twice daily in men with androgenetic alopecia (Shin 2007). Tretinoin was shown in one trial to promote hair regrowth more effectively when combined with minoxidil than when used alone (Bazzano 1986). However, retinoid use is associated with skin irritation that frequently leads to discontinuation (Baldwin 2021).

Topical Caffeine

Early research indicates topical caffeine may stimulate hair follicles and have positive effects on hair growth. In laboratory studies using hair follicle samples, caffeine has been found to promote hair growth and lengthen the anagen phase, block the inhibitory effect of testosterone, and counter the negative effect of corticotropin-releasing hormone (CRH, a stress hormone secreted by the hypothalamus) (Fischer 2007; Fischer 2014; Fischer 2021). In addition, a coffee extract was shown to stimulate proliferation and migration of dermal papilla cells and upregulate several hair growth pathways (Muangsanguan 2023). Caffeine’s positive effect on hair may result from inhibition of 5-alpha reductase, the enzyme involved in converting testosterone to DHT. It may also enhance blood flow to hair follicles (Elias 2023; Ufomadu 2024).

A group of researchers reported 12 weeks of treatment with a topical liquid containing caffeine, zinc, and a botanical combination called Procapil improved self-reported improvement in hair coverage in 19 men with androgenetic alopecia. In addition, the anagen-to-telogen ratio increased, but this effect did not reach statistical significance (Samadi 2024). An uncontrolled trial in 77 subjects with androgenetic alopecia found use of a shampoo containing 0.4% caffeine and 0.2% adenosine three times weekly for three months increased hair density (Chen 2024). An open-label trial in 210 men with androgenetic alopecia found a 0.2% caffeine solution was as effective as a 5% minoxidil solution for improving hair growth after six months (Dhurat 2017).

In an uncontrolled trial involving 30 women with stress-induced telogen effluvium, six months of treatment with a shampoo containing 10 mg/mL of caffeine improved subjective and objective measures of hair loss (Sisto 2013). The same research team also conducted two preliminary, randomized, placebo-controlled trials and found daily use of a caffeine-containing shampoo for six months reduced hair loss intensity, increased hair strength and thickness, and improved hair-pull test performance in women and men with androgenetic alopecia (Sisto 2013; Bussoletti 2020).

Platelet-Rich Plasma Injections

Plasma—the fluid in which blood cells are suspended—contains proteins, glucose, electrolytes, and other compounds. Plasma enriched with platelets, called platelet-rich plasma, is an abundant source of growth factors and can be used to promote cell proliferation and tissue regeneration. It is generally made from blood samples taken from the patient in whom it will be used, and has demonstrated beneficial effects in wound care, scar repair, and cosmetic surgery, as well as in hair loss disorders (Liu 2024; Mercader-Ruiz 2024).

A meta-analysis of findings from 10 randomized controlled trials found platelet-rich plasma therapy increased hair density in people with androgenetic alopecia, and the effect was stronger in men (Li 2024). In another meta-analysis that included data from 21 randomized controlled trials involving 628 women, platelet-rich plasma was found to increase hair density and thickness and improve hair-pull test performance in women with various types of hair loss (Yuan 2024). Furthermore, a meta-analysis of six randomized controlled trials with a total of 343 participants with androgenetic alopecia found a combination of platelet-rich plasma injection therapy plus topical minoxidil was more effective than either alone (Xiao 2024).

Platelet-rich plasma for hair growth is administered as multiple scalp injections, which can trigger anxiety in some individuals. Pain, bleeding, or infection at injection sites are potential adverse side effects (Liu 2024).

Stem Cell-Based Therapies

Stem cells promote tissue repair and regeneration by stimulating cell proliferation and migration, as well as through anti-inflammatory and immune-modulating effects (Liu 2024). Emerging clinical trials involving stem cells from human hair follicles, adipose tissue, bone marrow, umbilical cord blood, and teeth have found stem cell therapy can promote hair growth in subjects affected by androgenetic alopecia, although the effect seems to be temporary in some cases (Gasteratos 2024). In addition, stem cell-based therapies have been reported to be helpful in cases of alopecia areata and telogen effluvium (Ahn 2021; Hawwam 2022).

In a randomized controlled trial, 33 male and female subjects with androgenetic alopecia were treated with injections of hair follicle stem cells (collected from their own scalp tissue) and placebo (saline) in six different scalp regions three times at 45-day intervals. Twenty-three weeks after the last injection session, stem cell-treated regions showed a 33% increase in hair density, and at 44 weeks, the improvement had decreased somewhat to 27% (Gentile, 2019). Another trial followed the same protocol in 27 patients with androgenetic alopecia; more than a year after the last injection, the stem cell-treated regions showed substantially greater hair count and hair density. After 26 months, six participants (22%) were experiencing active hair loss again and required more treatment (Gentile 2020).

Signaling molecules secreted by stem cells may be sufficient to stimulate hair growth. In an uncontrolled trial involving 21 men and 19 women with hair loss, once-monthly scalp injections of a cell-free solution that had been pre-treated with adipose-derived stem cells increased hair density, raised the proportion of hair in the anagen state, and improved measures of scalp health after six months (Narita 2020).

Specialized hair follicle cells known as dermal papilla cells can activate stem cells and may be useful in restoring hair follicles and hair growth. Both dermal papilla cells and dermal sheath cells, another type of cell found at the base of hair follicles, are necessary for new hair follicle formation and hair growth (Liu 2024). In a randomized controlled trial involving 50 men and 15 women with androgenetic alopecia, participants received single injections of three different doses of human dermal sheath cells and placebo in four different regions of their scalps. After nine months, scalp regions treated with the lowest dose of dermal sheath cells had increased hair density compared with placebo in both men and women, and no serious adverse side effects occurred. However, this effect was temporary, and the effect was no longer seen after nine months (Tsuboi 2020). Another randomized controlled trial in 50 men and women with androgenetic alopecia found injections containing dermal papilla and dermal sheath cells increased hair number and diameter more than placebo injections after one month, and the effect was sustained for three months (Gan 2024).

Microneedling and Fractional Radiofrequency

Scalp microneedling therapy involves the use of a device such as a roller or stamp with tiny needles on its surface that is gently applied over the scalp (English 2022; Liu 2024). This stimulates a wound healing response that is thought to promote the release of growth factors and activate hair follicle cells such as dermal papilla and stem cells, leading to hair growth (Liu 2024). Clinical trials indicate microneedling may have beneficial effects in androgenetic alopecia and alopecia areata patients (English 2022). Microneedling can also be used to increase penetration of topical therapies including minoxidil, corticosteroids, and platelet-rich plasma (Liu 2024). A meta-analysis of 13 randomized controlled trials involving 696 subjects with androgenetic alopecia found microneedling plus monotherapy was more effective than either alone (Pei 2024).

Fractional radiofrequency involves the delivery of high-frequency radio waves through tiny pins on a comb-like applicator, stimulating a healing response and warming the tissue beneath the skin surface (Verner 2017; Kincaid 2023). Clinical reports indicate fractional radiofrequency therapy can stimulate hair growth in androgenetic alopecia and alopecia areata patients, increasing hair density and hair shaft thickness (Kincaid 2023). In one uncontrolled trial, 25 participants with androgenetic alopecia received 10 fractional radiofrequency treatments at two-week intervals. Two months after the last treatment, hair density had increased by an average of 31.6% and hair shaft thickness had increased by 18%; all participants tolerated the treatments well (Verner 2018). Fractional radiofrequency therapy also appears to increase uptake of topical minoxidil and corticosteroids, possibly enhancing their effectiveness (Kincaid 2023; Liu 2024).

Methods to Enhance Drug Delivery

Iontophoresis is a technique in which a small electrical charge is applied to the skin to facilitate the penetration of charged molecules past the superficial layers of the skin. This not only enhances drug delivery and effectiveness, but also reduces the risk of skin irritation from topical therapies (Liatsopoulou 2023). In preclinical research, iontophoretic delivery of minoxidil sulfate (an ionizable, or chargeable, form of minoxidil) was found to increase minoxidil accumulation in the hair follicle five-fold (Gelfuso 2013). In a clinical trial, four sessions of treatment with iontophoretically-delivered growth factors every three weeks for 12 months led to improved measures of hair growth in 60 patients with androgenetic alopecia and associated telogen effluvium (Alessandrini 2021). Microencapsulation, a technique in which a substance is coated with a delivery-enhancing chemical, has also increased minoxidil concentration in hair follicles. Combining microencapsulation with iontophoresis or laser therapy appears to have potential for improving uptake and possibly effectiveness of minoxidil, but this hypothesis awaits verification in clinical trials (Gelfuso 2015; Melo-Guimaro 2024).

B vitamins

Forty-six women with diffuse alopecia received 200 mg per day of oral vitamin B5 plus daily intramuscular injections of vitamin B6 for 20–30 days. The treatment was repeated after six months and resulted in improved hair condition and reduced hair loss (Brzezinska-Wcislo 2001). Results from animal studies demonstrated vitamin B6, in combination with the amino acid L-cystine, prevented hair loss caused by the chemotherapy drug doxorubicin (D'Agostini 2007; D'Agostini 2013).

Severe biotin (vitamin B7) deficiency can occur as the result of certain genetic mutations, causing hair loss as well as several other serious health problems (Zempleni 2008). In one study, 38% of women with self-reported hair loss exhibited biotin deficiency (Trueb 2016). In dogs, biotin supplementation may help improve hair growth (Frigg 1989), but human clinical trials have yet to verify this finding. Some preliminary evidence suggests that biotin supplementation may help treat alopecia caused by the medication valproic acid (Famenini 2014).

Vitamin D

A growing body of evidence shows that vitamin D participates in regulation of the hair cycle (Amor 2010; Malloy 2011; Vegesna 2002; Aoi 2012). In a case series of 210 women with female pattern hair loss, over 60% had below-normal vitamin D levels (Siah 2016). Low serum vitamin D levels are associated with autoimmune disorders including alopecia areata (Mahamid 2014; Aksu Cerman 2014). Telogen effluvium has been associated with vitamin D deficiency (Cheung 2016), and low vitamin D levels have been linked to greater hair loss in women with telogen effluvium and female pattern hair loss (Rasheed 2013).

In a 12-week trial, 48 patients with mild-to-moderate alopecia areata were treated twice daily with a topical solution containing calcipotriol, a synthetic form of vitamin D. At the end of the trial, more than 62% of participants had 75% or better hair regrowth, and 27% of participants had 100% hair regrowth (Cerman 2015). The case of a 7-year old boy with alopecia areata is also compelling: after failing to respond to topical minoxidil plus hydrocortisone, the boy experienced complete hair regrowth after three months of treatment with topical calcipotriol (Kim, Lee, Kim 2012). A study on 20 children with alopecia areata and 34 healthy controls found that vitamin D levels were inversely related to alopecia severity scores—as vitamin D levels went up, alopecia severity scores went down (Unal 2017).

Animal and preclinical models indicate topical vitamin D as well as calcipotriol may help prevent chemotherapy-induced alopecia, with some evidence suggesting this treatment can enhance hair regrowth (Jimenez 1992; Schilli 1998; Paus 1996; Wang 2006). In one study, topical vitamin D significantly reduced chemotherapy-induced hair loss in female mice (Chen 1998).

Saw Palmetto

Saw palmetto (Serenoa repens) is popularly used to treat prostate enlargement and androgenetic alopecia (Murugusundram 2009). A randomized controlled trial in 26 men aged 23‒64 with mild-to-moderate androgenetic alopecia found a combination of 200 mg saw palmetto extract, 50 mg beta-sitosterol, along with complementary amounts of lecithin, choline, inositol, niacin, and biotin was effective for measures of hair growth and quality. Self-assessment of satisfaction with hair growth and appearance, and investigative staff assessment of hair density both markedly improved (Prager 2002). An uncontrolled study in 50 men aged 20 to 50 years with androgenetic alopecia found a topical saw palmetto extract increased hair count (Wessagowit 2015). Another trial compared the effects of 320 mg oral saw palmetto extract daily to 1 mg finasteride daily in 100 men with mild-to-moderate androgenetic alopecia over two years. Finasteride led to hair regrowth in 68% of subjects, while 38% of those in the saw palmetto group experienced improved hair growth; treatment with saw palmetto was well tolerated (Rossi 2012). Researchers believe saw palmetto’s ability to inhibit 5-alpha reductase is at least partly responsible for its positive effects (Murugusundram 2009), and some have proposed that combining saw palmetto or beta-sitosterol with anti-inflammatory agents such as carnitine and alpha-lipoic acid may enhance its effectiveness (Chittur 2011; Chen, Wang, Mouser 2016).

Essential Fatty Acids

A trial in 120 women with early-stage hair loss found six months of daily supplementation with 460 mg fish oil, 460 mg black currant seed oil (providing gamma-linolenic acid [GLA]), 1 mg lycopene, and small amounts of vitamins E and C led to improved hair density compared with a control group. The supplemented group also had more anagen-phase hair and less telogen-phase hair compared with placebo (Le Floc'h 2015).

In a rodent study, most animals taking docosahexaenoic acid (DHA), an omega-3 fatty acid found mainly in fish oil, were protected from chemotherapy-induced alopecia (Takahata 1999). In another study of six rhesus monkeys with hair loss, daily treatment with omega-3 (72 mg) and omega-6 (26 mg) fatty acids was associated with decreased alopecia (Hamel 2017). Several studies have found attaching DHA to paclitaxel (Taxol), a commonly used chemotherapy drug, reduced the drug’s toxic side effects, including alopecia (Bradley 2001; Wolff 2003; Harries 2004).

Solubilized Keratin

Protein deficiency is a well-established cause of hair loss, and one protein, keratin, is the main component and primary structural element of hair. Age-related decline in keratin synthesis may lead to deterioration of the stability and flexibility of the hair shaft (Giesen 2011; Mubki 2014). This could leave hair vulnerable to dryness and breakage with brushing and use of styling products and tools.

In one study, a supplement containing a novel form of solubilized keratin (Cynatine) plus vitamins and minerals was compared with placebo in 50 women who had signs of stressed or damaged hair. Cynatine contains a specially-processed, highly bioavailable peptide form of keratin, a rich source of cysteine. After 90 days, the Cynatine formula group had less hair loss; improved hair strength; improved anagen phase, telogen phase, and anagen:telogen ratio; and better hair appearance compared with placebo (Beer 2014).

Silicon

Silicon, a trace element present in the body in small quantities, is thought to function as a structural component of hair (Martin 2013). Silicon compounds are common in many edible plants (Jurkic 2013). Two studies have looked at the effect of supplementing with orthosilicic acid, which provides silicon, on hair health. In one study, 50 women were given 10 mg orthosilicic acid or placebo daily for 20 weeks. By the end of the study, hair brittleness decreased in women receiving the silicon supplement (Barel 2005). In the second study, 48 women with fine hair received the same compound or placebo for nine months; hair strength and elasticity were better preserved and hair thickness increased in the supplemented group compared with placebo (Wickett 2007).

Zinc

Zinc deficiency has been associated with hair loss (Saper 2009; Kil 2013). Zinc plays an important role in normal hair follicle activity, preventing follicle regression and enhancing follicle recovery (Kil 2013). Also, zinc may act as an anti-androgen and modulator of 5-alpha reductase (Gupta 2014).

Men and women with androgenetic alopecia, telogen effluvium, and alopecia areata have all been found to have lower serum zinc levels than people with no hair loss (Kil 2013). Early research suggests using supplements to correct zinc deficiency in people with related telogen effluvium can improve hair loss (Karashima 2012).

Lower zinc levels in patients with alopecia areata have been correlated with increased severity, longer duration, and higher likelihood of treatment resistance (Abdel Fattah 2016; Bhat 2009). In one uncontrolled clinical study, 15 subjects with alopecia areata and low zinc levels (≤ 70 mcg/dL) received 50 mg zinc gluconate per day. After 12 weeks, hair regrowth was seen in nine subjects and was correlated with improved zinc status (Park 2009). In addition, case reports suggest continued zinc gluconate supplementation may help maintain hair recovery after treatment of alopecia areata in those who respond to ultraviolet light therapy plus zinc (Lux-Battistelli 2015).

Tocotrienols

Tocotrienols—members of the vitamin E family—are naturally found in barley, wheat germ, and certain types of grains and nuts (Ahsan 2015). Similar to tocopherols, the more familiar form of vitamin E, there are four tocotrienols labeled alpha, beta, gamma, and delta (Ahsan 2015; Peh 2016). Tocotrienols are recognized to have important vitamin E activity, particularly with regard to their anti-inflammatory, cholesterol-lowering, and radioprotective properties (Peh 2016; Jiang 2014).

Emerging evidence suggest tocotrienols may help promote healthy hair. In a study involving 38 women and men with various types and degrees of hair loss, those receiving supplements with 23 IU alpha-tocopherol plus 50 mg mixed tocotrienols experienced > 34% increase in hair numbers over eight months, while those receiving placebo experienced a slight decrease in hair numbers (Beoy 2010).

Green Tea

There is evidence that green tea and its main polyphenol, epigallocatechin gallate (EGCG), may help prevent hair loss and aid in hair regrowth. In a mouse study, a topical EGCG solution protected against testosterone-induced hair loss (Kim 2011). In a study in mice with spontaneous hair loss, a green tea polyphenol solution added to drinking water promoted hair growth versus no growth with plain water (Esfandiari 2005). EGCG stimulated dermal papilla cells and promoted hair growth in human hair follicles in a laboratory setting as well as in human subjects (Kwon, Han 2007).

Selenium

Selenium intake is important for healthy hair follicle function, and selenium deficiency may play a role in hair loss (Sengupta 2010; Hwang 2011). In an eight-week randomized controlled trial in 64 women with polycystic ovary syndrome, 32 received 200 mcg supplemental selenium daily while the other half received placebo. At the end of the trial, the selenium group had a significant reduction in hair loss compared with placebo (Razavi 2016).

Topical Melatonin

Melatonin may be helpful as a topical treatment for hair loss. While not yet known how melatonin might combat alopecia, its ability to counteract oxidative stress, thought to play an important role in hair loss (Trueb 2009), and its ability to stimulate hair follicle growth (Fischer 2012) have been suggested.

In an early controlled trial, 40 women with female pattern hair loss or diffuse alopecia applied 1 mL of either a 0.1% topical melatonin solution or placebo solution to their heads nightly. After six months, the topical melatonin group had significantly more hair in anagen phase (Fischer 2004).

A set of four studies in men and women with early-stage androgenetic alopecia evaluated melatonin combined with other topical agents as a treatment for hair loss. In the first study, a 0.0033% melatonin solution, also containing biotin and a Ginkgo biloba extract, was applied nightly to the scalps of 30 men and women for 90 days. Both investigators and participants reported a decrease in severity of alopecia on day 30 and an even greater improvement on day 90. In the second study, 35 men used the same solution nightly for six months. Investigators noted an average 29% increase in hair number and density after three months and an almost 43% increase in number and 41% increase in density after six months, with more than 50% of participants responding to treatment. The third study used a hair count test, in which participants counted the number of hairs lost during 60 seconds of combing each morning, as the measure of response. Lost hair counts decreased over the 90-day trial in 20 female participants but not in 40 male participants using the melatonin solution. The final study included 901 men and 990 women who applied the solution nightly. Hair pull tests showed no hair loss in nearly 62% and new hair growth in nearly 23% of participants after 90 days of treatment. In addition, treatment with melatonin solution appeared to improve seborrhea (red, itchy, scaly skin) in participants with this condition of the scalp (Fischer 2012).

Iron

Iron deficiency can cause telogen effluvium (Grover 2013; Levy 2013; Malkud 2015). Low levels of ferritin, an iron-storing protein, have been observed in women with female pattern hair loss (Park 2013; Rasheed 2013), telogen effluvium (Moeinvaziri 2009; Rasheed 2013), and premenopausal hair loss (Deloche 2007). One study found lowest ferritin levels were associated with most severe hair loss. Assessment of iron status, and iron supplementation if necessary, can be considered in women with hair loss (Rasheed 2013).