Causes and Risk Factors
Risk of hair loss increases with age and is higher in those with a family history of hair loss (Mayo Clinic 2015). While men have higher rates of androgenetic alopecia, women have a higher risk of telogen effluvium (Qi 2014).
Causes of Hair Loss
Causes of hair loss generally fall into five categories: hereditary, hormonal, medical, drug-related, and nutritional:
- Hereditary causes. Heredity is an important influence on age of onset, rate, and degree of hair loss (Mayo Clinic 2015).
- Hormonal causes. Hair loss is more common at times of hormonal changes such as during pregnancy, after childbirth, and with menopause. Even the onset of puberty can mark the beginning of hair loss in some men (Mayo Clinic 2015). Other hormonal causes of hair loss include polycystic ovary syndrome (PCOS) and thyroid disease (Mayo Clinic 2015; Goodman 2015; Levy 2013).
- Polycystic ovary syndrome. Polycystic ovary syndrome (PCOS), which affects about 5–10% of women, can lead to female pattern hair loss (Herskovitz 2013; Quinn 2014; Madnani 2013).
- Thyroid abnormalities. Both hyper- and hypothyroidism, as well as autoimmune thyroid disease with normal levels of thyroid hormone, are associated with alopecia areata (Lyakhovitsky 2015; Branisteanu 2014).
- Medical causes. Several medical conditions can cause hair loss:
- Some autoimmune diseases (Chen, Wang, Lin 2016)
- Tinea capitis, a fungal infection of the scalp (Ahanogbe 2015), psoriasis, seborrhea, and allergic contact dermatitis (Harrison 2009; Mubki 2014a)
- Trichotillomania (a psychological disorder characterized by hair pulling) (Ahanogbe 2015)
- Liver or kidney failure (Harrison 2009)
- Inflammatory bowel disease (Harrison 2009)
- Chronic infections such as HIV (Harrison 2009)
- Severe physical or emotional trauma (Harrison 2009; Ahanogbe 2015)
- Heavy metal poisoning (Harrison 2009)
- Drug causes. Most drug-induced hair loss is reversible, and is generally due to telogen effluvium or anagen effluvium (Piraccini 2006; Tosti 2007). Many different medications have caused cases of hair loss, with only a few regularly causing this side effect. Cancer chemotherapy drugs, on the other hand, cause hair loss in most people who take them (Santos 2015; Llau 1995). Radiation therapy is another potential cause of hair loss in cancer patients (Qi 2014). General anesthesia during surgery has been associated with telogen effluvium (Desai 1984), although general stress associated with surgery may contribute as well. Some other drug categories that may cause hair loss include (Llau 1995; Mubki 2014a):
- Oral contraceptives
- Anti-thyroid medications
- Anti-seizure medications
- Mood stabilizers
- Antimicrobial and antiviral medications
- Nutritional causes. Severe protein and essential fatty acid deficiencies; overall malnutrition and crash diets; and iron, zinc, biotin, and vitamin D deficiencies can cause hair loss (Harrison 2009; Mubki 2014a).
Other contributing factors. Unhealthy scalp and hair care practices can contribute to hair loss. The following practices may help prevent unnecessary hair damage and loss (Mayo Clinic 2015; AAD 2017):
- 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.