Common Cold

Common Cold

Last updated: 04/2020

Contributor(s): Colleen Mazin, MS/MPH; Dr. Maureen Williams, ND; Debra Gordon, MS

1 Overview

Summary and Quick Facts

  • It has been estimated that the U.S. population contracts approximately 1 billion colds per year. The common cold is a leading cause of medical visits and missed days at work or school.
  • Treatment strategies for the common cold are generally aimed at relieving symptoms, shortening duration and minimizing the risk of complications.
  • Several innovative and integrative strategies such as vitamin D, garlic, zinc, astragalus, beta glucan and probiotics have been shown in scientific studies to help manage symptom duration and intensity associated with the common cold.
  • Note: For information related to the 2019 novel coronavirus outbreak (SARS-CoV-2/COVID-19), please refer to our Protocol on that topic, here.

What is the Common Cold?

The common cold is a viral infection of the upper respiratory tract. Common colds may be caused by over 200 distinct viral pathogens, the most common being rhinovirus, coronavirus, and respiratory syncytial virus. Because there are so many distinct cold-causing viruses, developing immunity against the common cold is unlikely.

Infection occurs when the virus comes in contact with mucous membranes (eg, eyes, nose, mouth). Colds generally resolve without treatment, and conventional treatments are mostly palliative and aim to shorten the duration of the illness. An over-the-counter stomach acid medication, cimetidine, may augment the body’s immune response to viral pathogens and prevent colds from setting in.

Natural interventions such as vitamin D and zinc may help prevent the common cold and aid the body’s immune response.

What are Signs and Symptoms of the Common Cold?

  • Runny/stuffy nose
  • Sore throat
  • Coughing and sneezing
  • Low-grade fever
  • Mild aches

Note: Cold symptoms are usually mild and resolve within 7–10 days. If symptoms are more severe (eg, high fever, severe body aches), notify a healthcare provider as this may indicate a more serious condition, such as the flu.

What are Ways to Prevent the Common Cold?

  • Avoid contact with others while you have cold symptoms.
  • Direct coughs or sneezes into the crook of your elbow, not your hand or the air.
  • Avoid touching your eyes, nose, and mouth during cold outbreaks.
  • Wash and sanitize hands and surfaces.
  • Exercise regularly.
  • Get adequate sleep (quality and quantity).
  • Take extra around children, as they are more prone to colds. Be vigilant about hand hygiene and disinfecting surfaces.

What are Conventional Medical Treatments for the Common Cold?

  • DO NOT take antibiotics for a common cold. Antibiotics will not work against the common cold and can contribute to the development of drug resistant pathogens. Antibiotics are reserved for bacterial infections, such as secondary bacterial sinusitis.
  • Over-the-counter medications that may help relieve some cold symptoms include:
    • Oxymetazoline and pseudoephedrine for stuffy nose
    • Diphenhydramine for runny nose, sneezing, and coughing
    • Dextromethorphan for coughing
    • Mild analgesics such as acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs)

Note: Many cold medicines contain the same active ingredients. ALWAYS read labels to ensure you do not exceed the recommended dose.

What Natural Interventions May Be Beneficial for the Common Cold?

  • Vitamin D. Vitamin D has a significant role in regulating the immune system. Daily or weekly vitamin D and higher vitamin D levels are associated with a decreased risk of seasonal viral infection and acute respiratory infection.
  • Vitamin C. Vitamin C augments several aspects of the immune system and helps defend against infections. Using vitamin C may reduce the chances of catching a cold and cold duration.
  • Zinc. Zinc deficiency has been linked to immune impairment and susceptibility to infection; zinc can bolster the body’s ability to fight off viruses. Using zinc within 24 hours of symptom onset may reduce the duration and severity of a cold.
  • Dehydroepiandrosterone (DHEA). DHEA has powerful immune-enhancing and antiviral properties and can increase resistance to many experimental infections. Getting additional DHEA is likely to be important in elderly populations, as DHEA declines with age.
  • Melatonin. Melatonin helps combat many types of viral infections. Its administration is associated with increased production of antibodies and like DHEA, may be especially helpful in elderly populations.
  • Elderberry. Elderberry has been used for its medicinal properties since ancient times. Elderberry extracts are used for managing viral infections, such as the common cold.
  • Garlic. Allicin, a compound found in garlic, has demonstrated antiviral activity. Allicin-containing garlic may help prevent viral infection and reduce duration of cold symptoms.
  • Andrographis paniculata. Andrographis paniculata has been used for centuries among Asian cultures to treat colds. Standardized extracts can reduce symptoms of upper respiratory tract infection and may prevent colds as well.
  • Probiotics. Probiotics may help prevent infection and reduce the risk of catching a common cold. Some probiotics are also associated with reduced severity and duration of symptoms caused by common upper respiratory tract infections.
  • Other natural interventions that may be beneficial for common colds include Astragalus membranaceus, lactoferrin, beta-glucan, echinacea, honey, enzymatically modified rice bran, and quercetin.

2 Introduction


If you are reading this because you have developed cold symptoms, it is critical that you act quickly to halt the rapid replication of viruses occurring in your body at this very moment. Go to the nearest health food store or pharmacy and purchase:

  1. Zinc Lozenges: Completely dissolve in mouth one lozenge containing 18.75 mg of zinc acetate every two waking hours. Do not exceed 8 lozenges daily, and do not use for more than three consecutive days.
  2. Garlic: Take 9000-18,000 mg of high-allicin garlic each day until symptoms subside. Take with food to minimize stomach irritation.
  3. Vitamin D: If you don't already maintain a blood level of 25-hydroxyvitamin D over 50 ng/mL, then take 50,000 IU of vitamin D the first day and continue for three more days and slowly reduce the dose to around 5000 IU of vitamin D each day. If you already take around 5000 IU of vitamin D every day, then you probably don't need to increase your intake.
  4. Cimetidine: Take 800-1200 mg a day in divided doses. Cimetidine is a heartburn drug that has potent immune enhancing properties. (It is sold in pharmacies over-the-counter.)
  5. Melatonin: 3 to 50 mg at bedtime.

Do not delay implementing the above regimen. Once the cold virus infects too many cells, it replicates out of control and strategies like zinc lozenges will not be effective. Treatment must be initiated as soon as symptoms manifest! 


The common cold is a viral infection of the upper respiratory tract that causes symptoms such as a runny or stuffy nose, sneezing, coughing, and sore throat (Turner 2009; Turner 2011; Mayo Clinc 2011). Systemic symptoms such as mild headache, fatigue, fever, and muscle aches can occasionally occur with the common cold as well. However, if these symptoms are severe and/or accompanied by fever or significant exhaustion, they likely indicate the "flu", which is a distinct type of viral respiratory infection caused by an influenza virus (CDC 2011; Hayden 2011; NIAID 2011a).

It has been estimated that the U.S. population contracts approximately 1 billion colds per year, and the common cold is a leading cause of medical visits and missed days at work or school (Singh 2011; Roxas 2007). Although most cases of the common cold are mild and self-limiting, the illness represents a major economic burden to society in terms of lost productivity and treatment expenditure (Maggini 2012; Lissiman 2012; Turner 2009).

Treatment strategies for the common cold are generally aimed at relieving symptoms, shortening duration, and minimizing the risk of complications (Roxas 2007; Albalawi 2011).

Conventional cold treatments include over-the-counter analgesics and decongestant medications (Roxas 2007; NIH 2012b). However, these strategies are minimally effective (Nahas 2011), and even when used appropriately, may be associated with significant side effects (Shefrin 2009).

A number of specific antiviral drugs have some degree of effectiveness against common cold viruses. One exciting candidate is Biota's vapendavir, which recently met key milestones for benefit in a Phase IIb human rhinovirus trial in asthmatic patients in March, 2012 (EvaluatePharma 2012). The readily available over the counter (OTC) drug cimetidine, approved for the treatment of reflux and "heartburn", has anti-viral properties as well, and may be a useful common cold treatment.

Several innovative and integrative strategies such as vitamin D, garlic, zinc, Astragalus, beta glucan, and probiotics have been shown in scientific studies to help manage symptom duration and intensity associated with the common cold (Maggini 2012).

3 Development and Progression of the Common Cold

While the common cold may be caused by over 200 distinct and continually evolving viral pathogens; rhinoviruses, coronaviruses and respiratory syncytial viruses appear to be some of the most common (Turner 2009; Nussenbaum 2010; Worrall 2011; CDC 2012C).

Infection occurs when the cold-causing virus comes into contact with mucous membranes in the nose or eyes. Common cold infections generally result in a non-specific acute inflammatory response that stimulates the release of various inflammatory cytokines and other immune mediators. In fact, many of the symptoms associated with the common cold are a result of inflammation caused by this immune response, rather than by the virus itself (Turner 2009; Turner 2011; Hayden 2011; Pappas 2009). For example, the release of a proinflammatory peptide called bradykinin is a major contributor to sore throat symptoms (Turner 2009; Proud 1988). Stuffy nose symptoms result from increased pooling of blood in nasal blood vessels and increased nasal secretions. Likewise, runny nose occurs due to enhanced permeability of nasal blood vessels, which allows serum to leak into the nasal mucosa (Turner 2011).

Although infection with a virus known to cause the common cold generates an adaptive immune response that helps protect against repeated infection by the same or very similar virus, the sheer volume of distinct viruses that can cause the common cold makes developing immunity against the common cold itself very challenging (Hayden 2011; Turner 2009, Turner 2011). However, infection by a cold virus can decrease the risk and severity of re-infection with the same virus (Turner 2009).

New Understanding of the Human Immune System Paves Way for Potential Common Cold Treatment

For at least the last 100 years it has been assumed that the ability of antibodies produced by the immune system to protect against pathogens ends at the cellular membrane. In other words, scientists have thought that once a virus enters a cell it escapes the attack of antibody-mediated immunity, leaving only one option to eliminate the virus – kill the cell that harbors it. However, emergent research suggests this is not the case.

A specialized protein within cells called TRIM21 has been shown to bind to virus-bound antibodies within the cell and initiate an intracellular immune response (McEwan 2011).

Researchers have proposed that delivery of exogenous TRIM21, perhaps as a nasal spray, may help up-regulate immunity against some cold-causing viral pathogens and eliminate them in as little as a few hours (Mallery 2010; Connor 2010).

Although more research is needed before these findings can be applied clinically, the discovery of an intracellular defense system against viruses opens the door to promising new interventions for the common cold and other viral diseases.

4 Common Cold Symptoms

The clinical symptoms of the common cold generally occur within 24-72 hours of infection, and typically begin with runny nose and a sore or "scratchy" throat. Sore throat symptoms usually subside by the 2nd or 3rd day of infection, after which nasal symptoms typically become the most bothersome (Turner 2009; Turner 2011; Hayden 2011; Nussenbaum 2010). Three out of every 10 people with the common cold may develop an unproductive cough, often beginning after the onset of nasal symptoms, and persisting as the cold resolves (Turner 2009; Turner 2011; Hayden 2011; Nussenbaum 2010). As a whole, these symptoms may last anywhere from 2 to 14 days, but most people recover within 7 to 10 days. Nasal symptoms lasting longer than 2 weeks may be due to seasonal allergies rather than the common cold (NIAID 2011b).

Occasionally, common cold infections are associated with other complications such as ear and/or sinus infection. The common cold has also been known to exacerbate certain diseases of the upper respiratory tract such as asthma, bronchitis, cystic fibrosis, and COPD. Patients who experience high fever, intense sinus pain, severely swollen glands, and/or cough that produces mucus (i.e., productive cough) may have a more serious illness, and should notify their health care provider immediately (NIAID 2011b; Turner 2011; Roxas 2007d; Niespodziana 2012).

Common Cold vs. The Flu: Comparison of Characteristics




Etiological Agent

>200 viral strains; rhinovirus most common

3 strains of influenza virus: influenza A, B, and C

Site of Infection

Upper respiratory tract

Entire respiratory system

Symptom Onset

Gradual: 1-3 days

Sudden: within a few hours

Fever, chills

Occasional, low grade (<101° F)

Characteristic, higher (>101° F),

lasting 2-4 days


Infrequent, usually mild

Characteristic, more severe

General aches, pains

Mild, if any

Characteristic, often severe and affecting the entire body

Sore throat

Common, usually mild

Sometimes present

Cough, chest congestion

Common; mild-to-moderate, with hacking, productive cough

Common; potentially severe dry, non-productive cough

Runny, stuffy nose

Very common, accompanied by bouts of sneezing

Sometimes present

Fatigue, weakness

Mild, if any

Usual, may be severe and last 2-3 weeks

Extreme exhaustion


Frequent, usually in early stages of illness


Year around, peaks in winter months

Most cases between November and February

Antibiotics helpful?

No, unless secondary bacterial infection develops

No, unless secondary bacterial infection develops

(Roxas 2007; MD Consult 2012c; Utah Dept. Health 2010; CDC 2011; Oklahoma State Dept. of Health 2011)

5 Common Cold Prevention

Suggestions for preventing the common cold include:

Avoid others while you have cold symptoms and are contagious (i.e., 2-7 days) - Depending on the offending virus, the common cold may be transmitted from one person to another via inhalation. This is because viral particles are small enough to be suspended in the air when an infected person coughs, sneezes, or blows their nose. Since some viruses can live for up to 3 hours on human skin, the cold can also be transmitted via direct contact with an infected person (NIAID 2011c; Turner 2011; NIH 2012A).

Infected individuals should direct their cough or sneeze into the inner crook of their elbow, rather than into their hand(s) or directly into the air - The contagious particles from a cough or sneeze occasionally land on environmental objects or surfaces, where rhinoviruses can also survive for up to 3 hours (NIH 2012a; Nicas 2008; NIAID 2011c).

Avoid touching eyes, nose, and/or mouth during cold outbreaks - For most people this task is extremely difficult, especially since the average person touches their face approximately 16 times per hour. Given that unconscious face touching is almost unavoidable, hand washing/sanitizing and using surface disinfectants to prevent the spread of the common cold is important (NIH 2012a; Nicas 2008; NIAID 2011c).

Lifestyle modifications such as exercising have proven to be effective at reducing the number of common cold infections (NIAID 2011c). Individuals who become infected with mild to moderate cases of the cold should continue their exercise routine, provided their symptoms are not body-wide (Simon 2012).

Adequate sleep quantity and quality are important for protecting against common cold – Sleep is known to modulate the immune responses through the production of regulatory cytokines (Teodorescu 2012; Walsh 2011).

When possible, limit your exposure to children (particularly via day-care centers) during peak cold season – Since children are much more likely to contract a cold than adults (6-8 colds/yr. vs. 2-4 colds/yr., respectively), the adult risk of infection increases with increased contact with children, especially in close quarters (Lissiman 2012; Turner 2009). If this cannot be avoided, you should take extra precautions to wash/sanitize your hands and disinfect surfaces that may be contaminated (NIH 2012a; Nicas 2008; NIAID 2011c).

6 Conventional Treatment

Although the common cold is caused by viral infection, due to the sheer volume of potential common cold viruses and treatment timing, targeted anti-viral drugs are not typically beneficial (Pappas 2009). In addition, antibacterial drugs (i.e., antibiotics) are of no benefit in the treatment of the common cold (Turner 2009), except for in severe cases involving complication such as secondary bacterial sinusitis (Nussenbaum 2010). In fact, the use of antibacterial medications for treating uncomplicated colds is likely to do more harm than good, as they can induce adverse reactions as well as contribute to the development of drug resistant pathogens (CDC 2012b).

Over-the-Counter Cold Medicines Nearly $3 billion worth of OTC cold medicines are purchased each year, but randomized trial evidence suggests minimal effectiveness (Turner 2009; De Sutter 2009; Barrett 2007).

The following list comprises commonly used over-the-counter cough and cold medications along with their specific indications (Turner 2009; Simasek 2007; Dealleaume 2009):

Oxymetazoline and pseudoephedrine – These drugs are alpha-adrenergic agents. When use topically or orally, these agents may help relieve stuffy nose symptoms by causing blood vessels to constrict (Atkins 2011). Decongestants like pseudoephedrine can increase blood pressure and should not be used by people with hypertension (Simasek 2007).

Diphenhydramine – Diphenhydramine blocks the effects of histamine in the body, which is a proinflammatory component of the immune system. It may be beneficial for treating runny nose, sneezing, coughing, and nausea (Turner 2009; Clinical Pharmacology 2012a; MD Consult 2012a). Diphenhydramine also causes sedation and may cause arrhythmia and/or tachycardia and so should be used with caution by people who have heart problems (Simasek 2007).

Dextromethorphan – Dextromethorphan is a cough suppressant drug. It appears to reduce coughing via several actions within the brain (Clinical Pharmacology 2012b; MD Consult 2012b). Potential side effects of dextromethorphan include confusion, excitability, gastrointestinal disturbances, irritability, nervousness, and sedation (Simasek 2007).

Mild Analgesics - Acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs) (e.g., aspirin, ibuprofen, and naproxen) are drugs that provide analgesic, fever-reducing, and anti-inflammatory effects. These drugs may help alleviate painful symptoms such as a sore throat or muscle pain associated with the common cold (Turner 2009). It is important to consider that acetaminophen is an ingredient in many OTC cold medicines and can be toxic if consumed in excess. Therefore, it is imperative to read the labels of cold medicines carefully to avoid excess consumption of acetaminophen. Life Extension suggests that at least 600 mg of N-acetyl cysteine be taken with each dose of acetaminophen to help the liver detoxify harmful metabolic derivatives of the drug. More information is available in the Acetaminophen and NSAID Toxicity protocol.

People taking combination cough and cold medicines should be conscious of all the ingredients and doses contained within (e.g., some products contain up to 5 distinct ingredients), and make sure that they are not duplicating therapy or taking more than is recommended (Mayo Clinic 2012; Erebara 2008). Given that over-the-counter drugs have not been demonstrated to be beneficial for the treatment of cold in young children and their potential for toxicity, these medications are not recommended for children under 4 (Turner 2009).

Protecting Against the Common Cold with a Stomach Acid Medication Cimetidine is an over-the-counter drug that blocks certain histamine receptors (i.e., histamine receptor type 2 antagonist); it is approved by the FDA for inhibition of gastric acid secretion. In addition to its usefulness for treating gastric or duodenal ulcers (Scheinfeld 2003; Kubecova 2011), cimetidine has also been shown to augment immune response against viral pathogens (Shin 2012; Arae 2011; Wang 2008; Zhang 2011; Wang 2008; Stefani 2009).

One of cimetidine's important actions is inhibition of suppressor T-cells, which are cells of the immune system that normally "turn down" the immune response (Wang 2008; Li 2011). In other words, taking cimetidine at the first sign of a cold may allow for a more robust immune response by countering the effects of these intrinsic immune regulators.

New Drug Significantly Reduces Cold Symptoms in Clinical Trial

Results of a phase II clinical trial show that a new antiviral, vapendavir, reduced symptoms of rhinovirus infection among people with asthma (EvaluatePharma 2012).

Vapendavir works by blocking entry of viruses into host cells, thereby preventing infection.

Compared to those who took a placebo, vapendavir recipients experienced significantly less cold symptoms during days 2 and 4 of infection, when symptoms are typically worst. Moreover, those who took the new drug experienced earlier improvement of symptoms compared to those who took a placebo (1.7 days vs. 2.5 days).

More trials are needed before vapendavir becomes widely available as a common cold treatment, but these early results are encouraging.

7 Targeted Nutritional Therapies

After infection, viruses causing the common cold multiply rapidly. While most people wait until their symptoms become unbearable, then use an over-the-counter medication, Life Extension recommends aggressive action when the viral count is still relatively low and symptoms are mild.

Vitamin D. Evidence suggests vitamin D has a significant role in the regulation of the human immune system, and may reduce the risk of certain bacterial and viral infections (Beard 2011; Grant 2010). Theoretically, vitamin D supplementation may produce a sufficient amount of cathelicidin (a naturally occurring antimicrobial and antiviral) to cure viral respiratory infections such as the common cold (Cannell 2008; Barlow 2011). Furthermore, data show that higher vitamin D levels are associated with a decreased risk of contracting a seasonal viral infection (Berry 2011; Cannell 2011). In a comprehensive review, researchers analyzed data from 10,933 participants in 25 randomized controlled trials looking at the effect of vitamin D on risk of acute respiratory infections, including common colds. The analysis found that those receiving daily or weekly vitamin D, in doses ranging from 300 IU to 4000 IU per day, had a 19% reduction in acute respiratory infection risk, and those with vitamin D deficiency (levels below 25 nmol/L or 10 ng/mL) at the beginning of the trial experienced a greater protective effect. A risk reduction was not seen in participants who received individual large doses of vitamin D (30,000 IU or more), either once or at intervals of one to three months, whether alone or in addition to daily or weekly doses (Martineau 2017). Life Extension recommends an optimal 25-hydroxyvitamin D blood level of between 50 and 80 ng/ml.

Vitamin C. Evidence shows that vitamin C augments several aspects of the immune system and helps defend against infections (especially viral infections) (Ely 2007; Holt 2010; Heimer 2009; Khalid 2011). Vitamin C enhances the production and action of white blood cells; for example it increases the ability of neutrophils (a type of white blood cell) to attack and engulf viruses (Heimer 2009; Jariwalla 1996; Anderson 1984). Vitamin C has been shown to reduce the chances of catching a cold, and may reduce cold duration (Holt 2010; Hemila 2011). Upon review of clinical data from 2 studies, researchers found that using vitamin C (1000 mg) plus zinc (10 mg) during a cold could reduce runny nose symptoms by up to 27 % over 5 days of treatment compared to placebo (Maggini 2012).

Zinc – Zinc helps maintain a healthy immune system, and zinc deficiency has been linked to significant immune impairment and susceptibility to infections (Roxas 2007; Maggini 2012). Unfortunately, zinc deficiency is a common problem affecting approximately 2 billion people worldwide, even many people in Western populations. Correcting zinc deficiency through supplementation has been shown to bolster aspects of the immune system involved in fighting viral infections (Maggini 2012; Sandstead 2010; Pae 2012). Zinc's antiviral properties may come from its ability to prevent the rhinovirus from attaching to cells in the nasal passages. In addition, zinc has been shown to prevent viral replication, reduce histamine release, and inhibit the production of other inflammatory mediators (Singh 2011).

A comprehensive review concluded that zinc was associated with a significant reduction in the duration and severity of the common cold (when administered within 24 hours of onset of symptoms). It was also found that zinc supplementation over 5 months was helpful for preventing the common cold (Singh 2011). Life Extension Magazine® published a comprehensive overview of the evidence suggesting that zinc acetate lozenges dissolved in the mouth every two waking hours may be an ideal approach during the early stages of the common cold.

DHEA. Dehydroepiandrosterone (DHEA) is a steroid hormone synthesized by the adrenal gland. Research has revealed that DHEA possesses powerful immune-enhancing and antiviral properties, and can enhance resistance to many different experimental infections (Romanutti 2010; Torres 2012; Kuehn 2011; Roxas 2007). DHEA accomplishes this in part by modulating several aspects of the immune system. For example, administering 50 mg of DHEA daily to an elderly population resulted in an increase in natural killer cell activity, a 62% increase in B cell activity and a 40% increase in T cell activity, all of which are important for defending against infectious pathogens (Roxas 2007).

DHEA supplementation is likely to be especially important among the aging and elderly, since DHEA levels decline sharply with age (Roxas 2007; Khorram 1997).

Melatonin. Melatonin is a hormone produced in the brain and the gut. It helps regulate the sleep-wake cycle and is a powerful antioxidant. Research indicates that melatonin helps combat many types of viral infections (Srinivasan 2012; Arushanian 2002; Boga 2012). For example, melatonin appears to "prime" the immune system by interacting with specialized immune cells called "T-helper cells", allowing for a more efficient immune response against pathogens. Furthermore, melatonin administration is also associated with an increased production of antibodies (Bonilla 2004).

Melatonin's role as an antioxidant may be helpful during a cold as well, since most viral infections are associated with high amounts of oxidative stress (Boga 2012). This may be especially true for elderly populations, since these patients frequently experience age-related impairment of the immune system, which coincides with declining melatonin concentrations (Srinivasan 2005).

Astragalus membranaceus. Astragalus membranaceus is a Chinese herb that contains a number of immune-stimulating ingredients such as polysaccharides, flavonoids, trace minerals, and amino acids. While it has been traditionally used to treat colds and flu as well as for increasing stamina and overall vitality, much of the research performed on Astragalus membranaceus is focused on its application for treating immune deficiency conditions (Roxas 2007; AMR 2003). In a clinical study comparing various natural products (i.e., echinacea, astragalus membranaceus, and licorice), Astragalus membranaceus demonstrated the strongest ability to activate immune cells (Roxas 2007).

Elderberry. Elderberry, also known as Sambucus nigra, has been used for its medicinal properties since at least 400 BC (Krawitz 2011; Roxas 2007). The purplish-black fruits of the elderberry plant are a rich source of antioxidants, and have long been considered a folk remedy for the treatment of influenza as well as the common cold (Ozgen 2010; Zakay-Rones 2004). Even today, elderberry extracts are commonly employed as an alternative to conventional drugs for the management of a variety of viral infections and are recognized as supportive agents against common cold (Krawitz 2011). Researchers believe that elderberry fights colds by activating white blood cells that engulf pathogens. The German Commission E (a therapeutic guide for the safety and efficacy of herbal products) has identified the constituents of elderberry as effective for the relief of colds (Roxas 2007).

Garlic. Garlic (i.e., allium sativum) has been traditionally used for both its culinary and therapeutic properties (Lissiman 2012). A clinical survey found that garlic is one of the most common herbs used for its medicinal properties including for the treatment of colds, flu, and cough (Zhang 2008). When raw garlic is chopped or chewed, it releases an active organo-sulfur compound called allicin, which has demonstrated antiviral activity against rhinovirus and a variety of other pathogens (Nahas 2011). While studies evaluating the use of garlic/allicin for the treatment of the common cold are lacking, evidence suggests it may be useful for the prevention of such infections (Nahas 2011). For example, one clinical study demonstrated that allicin-containing garlic taken once daily (over a 12-week period) was associated with 65% fewer colds than the placebo group (24 vs. 65). When compared with placebo, garlic/allicin was also linked to 70% reduction in symptom duration (~ 1.5 vs. 5 days) (Josling 2001).

Andrographis. Andrographis paniculata has been effectively used among Asian cultures for the treatment of colds for centuries (Chandrasekaran 2009; Ozolua 2011; Ji 2005; Akbar 2011; Valdiani 2012). It is reported to have anti-inflammatory, blood pressure lowering, antiviral, and immune-stimulant properties (Yang 2010). A 2009 study found that an extract of Andrographis enhanced immune function as well as reversed drug-induced immunosuppression (Naik 2009). Accumulating evidence suggests that Andrographis paniculata is effective as an alternative treatment option for the common cold (Coon 2004; Poolsup 2004; Kligler 2006). For example, a 2010 study found that a standardized extract of Andrographis paniculata was more than twice as effective as placebo in reducing symptoms of upper respiratory tract infections (Saxena 2010). Preliminary evidence suggests that Andrographis paniculata may be effective for the prevention of colds as well (Coon 2004).

Lactoferrin. Lactoferrin is an iron-binding protein found in milk. It is a powerful immune modulator and has shown marked ability to fight bacteria, fungi, protozoa, and viruses (Roxas 2007; Orsi 2004; Lonnerdal 2009). Laboratory studies reveal lactoferrin inhibits viral infection by interfering with the ability of certain viruses to bind to cell receptor sites and prevents entry of viruses into host cells (Waarts 2005; Berlutti 2011). In addition, lactoferrin may be beneficial for alleviating the symptoms or complications of viral infections like the common cold, because it suppresses free radical-mediated damage (Roxas 2007).

Beta-glucan. Beta-glucans are naturally occurring glucose polymers that constitute the cell walls of certain plants and pathogenic agents (Akramiene 2007). These polysaccharides have been shown to increase host immune defense, and are associated with enhancing macrophage and natural killer cell function (Pence 2012; Akramiene 2007). Beta glucans also appear to mitigate the symptoms of the common cold. The Montana Center for Work Physiology and Exercise Metabolism examined beta glucans' ability to mitigate upper respiratory infections in a single blind, randomized trial in 2008. Participants who consumed beta-glucans had 23% fewer upper respiratory tract infections, compared to the group taking a placebo (PRNewswire 2008).

Probiotics. Probiotics are defined as living microorganisms (i.e., bacteria and fungi) that confer a health benefit to the host when administered in adequate amounts (Gilliland 2001; MacDonald 2010). Clinical studies suggest that certain probiotics may help prevent viral respiratory tract infections such as the common cold by enhancing the immune system. Some probiotics are associated with a reduction in severity and duration of symptoms caused by common upper respiratory tract infections (de Vrese 2008; MacDonald 2010; Wolvers 2010; Vouloumanou 2009; Baron 2009; Leyer 2009). Probiotics may be useful for managing infectious diseases because of their potential for stabilizing the micro-flora of the gut, enhancing resistance against pathogenic colonization, and modulating immune functions (Wolvers 2010; Kimmel 2010; Baron 2009). A 2011 clinical study found that a probiotic lactobacilli was able to strengthen the body's immune defense against viral infections and reduce the risk of acquiring the common cold (Berggren 2011). Furthermore, the consumption of yogurt fermented with Lactobacillus augmented natural killer cell activity and reduced the risk of catching common cold infections among the elderly (Makino 2010).

Echinacea. Echinacea is an herb that was first utilized for its medicinal value by the Native Americans in the treatment of cough, sore throat, and tonsillitis (Caruso 2005). Today, echinacea represents one of the most popular herbs used for the treatment and prevention of upper respiratory tract infections (like the common cold) in both European and American markets (Tierra 2007; Woelkart 2008; Toselli 2009). Clinical evidence shows that echinacea has beneficial effects on the common cold, including reduced severity and duration of cold symptoms, as well as increases in monocytes, neutrophils, natural killer (NK) cells, and total white blood cell count (Roxas 2007). A 2010 clinical study found that a standardized extract of E. purpurea was able reduce the risk of common cold among athletes (Ross 2010).

Honey. Honey has been used since ancient times as a cough and cold remedy in some countries (Pourahmad 2009). Studies have shown that honey possesses antimicrobial properties and helps combat infection in a variety of clinical settings (Al-Waili 2011). Clinical trials have compared the efficacy of honey to that of placebo and several conventional medicines for relieving symptoms of the common cold (Pourahmad 2009). Evidence suggests that honey can relieve symptoms of the common cold in adults and children more effectively than some, but not all, conventional medicines (Heppermann 2009; Paul 2007; Oduwole 2012; Cohen 2012).

Enzymatically modified rice bran. Enzymatically modified rice bran is made by fermenting rice bran with enzymes extracted from the shiitake mushroom (Lentinus edodes). Through the fermentation process, immunologically active polysaccharides, including one called arabinoxylan, become more bioavailable (Choi 2014).

Animal research provides support for the immune-stimulating ability of enzymatically modified rice bran. In an experimental model of immune senescence using aged mice, treatment with enzymatically modified rice bran led to increased NK cell activity (Ghoneum, Abedi 2004). And, in a study in rats, immune cells from those fed enzymatically modified rice bran for two weeks exhibited a stronger response to an immune challenge (Giese 2008).

A number of laboratory studies further demonstrate the immune-enhancing effects of enzymatically modified rice bran. Human natural killer (NK) cells treated with fermented rice bran extract increased their production of the immune-stimulating cytokines interferon-gamma and tumor necrosis factor-alpha (Ghoneum 2000). Human monocytes, macrophages, and neutrophils have been shown to increase their phagocytic activity (ie, engulfing and digestion of foreign substances) upon treatment with enzymatically modified rice bran (Ghoneum, Matsuura 2004; Ghoneum 2008). Enzymatically modified rice bran was also found to stimulate maturation and increase activity in human immature dendritic cells, which are immune cells that help activate other immune cells (Cholujova 2009; Ghoneum 2011; Ghoneum 2014).

Arabinoxylan from enzymatically modified rice bran may protect against the common cold in older people. In healthy individuals, arabinoxylan increased levels of interferon-gamma (Choi 2014), a cytokine essential to the body’s antiviral defenses (Chesler 2002). Arabinoxylan was found in one study to protect against upper respiratory viral infections (common colds) in older people. In a double-blind, placebo-controlled, crossover trial, 36 subjects between 70 and 95 years of age received both 500 mg arabinoxylan and placebo, each for six weeks. Scores measuring total common cold symptoms were three times higher and duration of symptoms twice as long in participants during the placebo phase compared with the arabinoxylan phase. In those with low NK cell activity, the increase in NK cell activity was more than double in the arabinoxylan group compared with placebo (Maeda 2004).

Quercetin. Quercetin is a flavonoid with anti-inflammatory, antioxidant, and antiviral properties. It is naturally found in foods such as apples, grapes, broccoli, kale, red onions, green tea, and wine. Research suggests quercetin may decrease infection risk, prevent histamine release, and support a balance between TH1 and TH2 cells, which regulate the immune system (Kinker 2014; Mlcek 2016; Li 2016). Cellular research suggests quercetin inhibits viral replication and reduces the overexpression of cytokines (Ganesan 2012). Quercetin may also enhance antiviral signaling and inhibit the enzymes involved in viral replication (Kinker 2014).

In an animal study, mice with a condition similar to COPD were given either rhinovirus or sham injections, followed by placebo or quercetin. The researchers examined the mice for lung inflammation and changes in lung mechanics. They found that quercetin in the COPD mice reduced viral load and rhinovirus-induced changes in the lungs. The authors suggested quercetin may inhibit viral replication, enhance viral clearance, and limit inflammatory responses to rhinovirus that worsen lung disease (Ganesan 2011). 

A randomized, double-blind, placebo-controlled trial of over 1,000 people compared 12 weeks of placebo and quercetin (at 500 and 1,000 mg/day, with 500‒1,000 mg of vitamin C and 20‒40 mg of niacin) in reducing rates of upper respiratory tract (URT) infections. While there was no significant difference in infection rates for all subjects (aged 18 to 85 years), a separate analysis of physically fit individuals aged 40 years and older found that 1,000 mg quercetin daily reduced URT infection severity and the number of sick days reported (Heinz 2010).

A randomized, double-blind, placebo-controlled study in which 40 trained male cyclists were given either quercetin (1,000 mg/day) or placebo one week before, during, and two weeks after a three-day period of intense exercise (three hours of cycling per day) found that quercetin significantly reduced URT infection incidence in the two weeks after intense exercise. The authors concluded that quercetin may reduce rates of respiratory illness in athletes after periods of heavy training (Nieman 2007).

Disclaimer and Safety Information

This information (and any accompanying material) is not intended to replace the attention or advice of a physician or other qualified health care professional. Anyone who wishes to embark on any dietary, drug, exercise, or other lifestyle change intended to prevent or treat a specific disease or condition should first consult with and seek clearance from a physician or other qualified health care professional. Pregnant women in particular should seek the advice of a physician before using any protocol listed on this website. The protocols described on this website are for adults only, unless otherwise specified. Product labels may contain important safety information and the most recent product information provided by the product manufacturers should be carefully reviewed prior to use to verify the dose, administration, and contraindications. National, state, and local laws may vary regarding the use and application of many of the therapies discussed. The reader assumes the risk of any injuries. The authors and publishers, their affiliates and assigns are not liable for any injury and/or damage to persons arising from this protocol and expressly disclaim responsibility for any adverse effects resulting from the use of the information contained herein.

The protocols raise many issues that are subject to change as new data emerge. None of our suggested protocol regimens can guarantee health benefits. Life Extension has not performed independent verification of the data contained in the referenced materials, and expressly disclaims responsibility for any error in the literature.

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