No one looks forward to the cold and flu season. Americans catch an estimated 1 billion colds each year. In fact, the common cold is among the leading reasons for visiting a doctor and for missing school or work. The flu, with its potential complications, can be an even greater concern. Each year, an estimated 5 to 20 percent of Americans come down with the flu. Although most recover without incident, flu-related complications result in more than 200,000 hospitalizations and 36,000 deaths annually.
In an effort to prevent or treat these all-too-common illnesses, some people turn to complementary and alternative medicine (CAM) approaches. This fact sheet provides basic information on colds and flu, as well as “what the science says” about some of these CAM approaches. If you are considering using a CAM therapy for colds or flu, this information can help you talk to your health care provider about it.
About the Common Cold
The common cold is a viral infection of the upper respiratory system. Many different viruses, including various types of rhinovirus, can cause colds. Children are especially susceptible, in part because their immune systems have not yet developed resistance to cold-causing viruses. Research suggests that stress can lower resistance to colds. Researchers are also looking at possible connections between a number of other factors—environmental and personal—and susceptibility to colds.
People can catch a cold by touching a virus-contaminated surface and then touching their eyes or nose, or by inhaling airborne droplets of infected mucus. Symptoms usually appear 1 to 3 days after exposure and include sneezing, runny or stuffy nose, sore throat, and cough. The average cold lasts a week. Although colds sometimes are mistaken for influenza, the two conditions are caused by different viruses, and only the flu is likely to involve a high fever and extreme fatigue.
The chances of catching a cold can be reduced by washing the hands frequently and avoiding contact with people who have colds. People with colds are advised to rest and drink fluids. Over-the-counter pain or cold medicines can help relieve symptoms. Antibiotics do not fight cold viruses. There is no vaccine to prevent the common cold, and there is no known cure.
CAM Practices People Use for Colds
People try many different CAM therapies in their efforts to fight colds (see Fighting Colds With CAM). According to estimates based on the 2007 National Health Interview Survey (NHIS), colds ranked eighth among adults and third among children as a medical condition prompting CAM use.
What the Science Says About CAM and the Common Cold
There is no conclusive scientific evidence that any CAM therapy prevents colds or substantially reduces their duration or severity in adults or children. Although some studies suggest possible benefits, overall evidence for specific CAM therapies is limited and/or mixed, and many studies have been methodologically flawed. Given the public health burden of the common cold, and the widespread use of some CAM therapies to fight colds, researchers continue to investigate potential CAM options, including the dietary supplements commonly used for colds—echinacea, vitamin C, and zinc.
Many people take echinacea supplements to prevent or treat colds. (In the 2007 NHIS, echinacea was the most commonly used natural nonvitamin/nonmineral supplement among children, and the third most commonly used supplement among adults.) These products vary widely, using different echinacea species, plant parts, and preparations. The many clinical trials of echinacea for colds have also varied widely, in terms of products studied, research methodology, and study results. Reviews of the research have found some limited evidence that echinacea may be useful for treating colds in adults. Results are less promising for children and for preventing colds. Three NCCAM-funded trials found no benefit from echinacea for preventing or treating colds. A 2008 evaluation of the research concluded that clinical data on echinacea so far are not conclusive and suggested directions for further research.
Evidence of vitamin C for the prevention and treatment of the common cold has been mixed. A 2007 analysis of results from 30 clinical trials involving 11,350 participants found that taking vitamin C regularly (at least 0.2 grams per day) did not reduce the likelihood of getting a cold, but was associated with slight reduction in the duration and severity of cold symptoms. Among participants in six trials who were exposed to extreme physical or cold stress (e.g., soldiers in subarctic conditions) and took vitamin C, a 50-percent reduction in the risk of getting a cold was seen. Analysis of several other trials involving adults who started vitamin C therapy after onset of cold symptoms did not find convincing evidence of an effect on duration or severity of colds. A 2009 review of the research on vitamins and minerals for colds concluded that vitamin C supplementation has shown some potential for treating colds; the review noted, however, that few therapeutic trials have been published (none studying children) and that more research is needed to determine optimal doses and treatment strategies. Vitamin C is generally considered safe; however, side effects have been reported when taken in high doses.
Zinc is present in a number of products sold as natural medicines for colds. In 2009, the U.S. Food and Drug Administration warned consumers to stop using intranasal zinc products (zinc-containing homeopathic cold remedies), because of case reports of nosmia (loss of smell). The effect of zinc on the severity or duration of cold symptoms is inconclusive; some studies find benefits, others do not. In a 2007 review of the research, three of the four studies that met all of the reviewers’ quality criteria found no therapeutic effect from zinc lozenges or nasal spray; one study reported positive results for zinc nasal gel. A study reported in 2008 found that zinc acetate lozenges reduced the severity and duration of cold symptoms, compared with placebo. A 2009 review of the research on vitamins and minerals for colds noted that variations in the results of zinc lozenge trials are related mainly to variations in dosage, and that doses of more than 70 mg per day have consistently reduced the duration of colds; the review concluded that zinc has shown potential for treating colds, and that additional research is needed to determine optimal doses and treatment strategies.
Echinacea, vitamin C, and zinc are not the only CAM therapies that people sometimes try in hopes of preventing colds or relieving cold symptoms. Here are some other examples:
North American ginseng (Panax quinquefolium)
South African geranium (Andrographis paniculata)
Umckaloabo (Pelargonium sidoides)
Scientific evidence to date does not support recommending any of these therapies for general use against colds. People should check with their health care provider before using any CAM therapy for colds-especially before treating a child.
About the Flu
Influenza (flu) is a contagious respiratory illness caused by influenza viruses. Seasonal flu outbreaks occur annually. Flu viruses are very changeable, and the common strains are different from year to year. Usually these changes are gradual; however, sometimes a new, potent strain (such as 2009’s H1N1 virus) emerges suddenly and causes a major flu epidemic, or even a pandemic—i.e., the illness becomes very widespread.
The flu is not the same as the common cold (different viruses are involved), and it is unrelated to what is often called “stomach flu.” Like colds, though, the flu spreads easily from person to person through virus-contaminated surfaces or through the air. Symptom onset is likely to be abrupt for the flu, more gradual for colds. Flu symptoms are usually more severe than cold symptoms and are likely to include fever (often high), headache, muscle and joint pain, and extreme fatigue. Young children, older adults, pregnant women, and people with certain chronic health conditions are at increased risk of flu-related complications such as pneumonia.
Vaccination is the best protection against contracting the flu. As with colds, the chances of catching the flu can also be reduced by washing hands frequently and avoiding contact with people who have the flu. If taken within 48 hours of symptom onset, the prescription antiviral drugs oseltamivir (Tamiflu®) and zanamivir (Relenza®) can reduce the severity and duration of flu symptoms.
CAM Practices People Use for the Flu
Although there are vaccines to prevent the flu, prescription drugs to treat it, and over-the-counter remedies that can help relieve symptoms, people may use CAM approaches—including various natural products and mind-body practices—in hopes of strengthening their resistance to flu viruses and recovering more quickly from bouts of the flu.
There is no conclusive scientific evidence that any CAM therapy is useful against the flu. Some studies suggest a potential role for certain therapies, but the evidence is very limited, and additional research is needed before any of these therapies can be recommended as safe and helpful in preventing or treating the flu. Research is ongoing in areas of CAM that may have relevance for combating the flu.
Examples of natural products that some people try in their efforts to combat the flu include elderberry, echinacea, North American ginseng, Chinese medicinal herbs, oscillococcinum, green tea, vitamin D, vitamin C, N-acetylcysteine (NAC), and dehydroepiandrosterone (DHEA). The mind-body practices sometimes used for flu include mindfulness meditation and tai chi.
NCCAM-supported researchers are conducting a variety of studies relevant to colds and flu. Examples of recent research include:
>Effects of echinacea, placebo, and doctor-patient interactions on the duration and severity of colds
Do not use any CAM therapy as a substitute for vaccination against the flu. There is no conclusive scientific evidence that any CAM therapy works to prevent or treat colds or the flu, but evidence is especially limited for the flu.
Talk to your health care providers. Tell them about the CAM therapy you are considering for preventing or treating colds or flu, and ask any questions you may have. They may know about the therapy and be able to advise you on its safety, use, and likely effectiveness.
If you are considering dietary supplements, keep in mind that they can act in the same way as drugs. They can cause medical problems if not used correctly or if used in large amounts, and some may interact with medications. Your health care provider can advise you. If you are pregnant or nursing a child, or if you are considering giving a child a dietary supplement, it is especially important to consult your health care provider. To learn more, see the NCCAM fact sheet Using Dietary Supplements Wisely.
Tell all your health care providers about any complementary and alternative practices you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care. For tips about talking with your health care providers about CAM, see NCCAM’s Time to Talk campaign.
Protecting Yourself and Your Family Against the Flu
According to the U.S. Food and Drug Administration, there are many unfounded claims for products to prevent or treat the flu. Vaccination is the best protection against contracting the flu. Visit the Web site Flu.gov for comprehensive information on the flu.
The NCCAM Clearinghouse provides information on CAM and NCCAM, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.
Toll-free in the U.S.: 1-888-644-6226
A service of the National Library of Medicine (NLM), PubMed contains publication information and (in most cases) brief summaries of articles from scientific and medical journals. CAM on PubMed, developed jointly by NCCAM and NLM, is a subset of the PubMed system and focuses on the topic of CAM.
NIAID conducts and supports research to study the causes of allergic, immunologic, and infectious diseases, and to develop better means of preventing, diagnosing, and treating these illnesses.
Web site: www3.niaid.nih.gov
NIH National Library of Medicine’s MedlinePlus
Managed by the U.S. Department of Health and Human Services, Flu.gov provides comprehensive government-wide information on seasonal, H1N1 (swine), H5N1 (bird), and pandemic influenza for the general public, health professionals, and others.