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Flu and Colds: In Depth

Flu and Colds: In Depth
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What’s the Bottom Line?

What do we know about the effectiveness of complementary approaches for flu and colds?

  • No complementary health approach has been shown to be helpful for the flu.
  • For colds:
    • Complementary approaches that have shown some promise include oral zinc products, rinsing the nose and sinuses (with a neti pot or other device), honey (as a nighttime cough remedy for children), vitamin C (for people under severe physical stress), probiotics, and meditation.
    • Approaches for which the evidence is conflicting, inadequate, or mostly negative include vitamin C (for most people), echinacea, garlic, and American ginseng.

What do we know about the safety of complementary approaches for colds and flu?

  • People can get severe infections if they use neti pots or other nasal rinsing devices improperly. Tap water isn’t safe for use as a nasal rinse unless it has been filtered, treated, or processed in specific ways.
  • Zinc products used in the nose (such as nasal gels and swabs) have been linked to a long-lasting or even permanent loss of the sense of smell.
  • Using a dietary supplement to prevent colds often involves taking it for long periods of time. However, little is known about the long-term safety of some dietary supplements studied for prevention of colds, such as American ginseng and probiotics.
  • Complementary approaches that are safe for some people may not be safe for others. Your age, health, special circumstances (such as pregnancy), and medicines or supplements that you take may affect the safety of complementary approaches.

Some Basics About Flu and Colds

Each year, Americans get more than 1 billion colds, and between 5 and 20 percent of Americans get the flu. The two diseases have some symptoms in common, and both are caused by viruses. However, they are different conditions, and the flu is more severe. Unlike the flu, colds generally don’t cause serious complications, such as pneumonia, or lead to hospitalization.

No vaccine can protect you against the common cold, but vaccines can protect you against the flu. Everyone over the age of 6 months should be vaccinated against the flu each year. Vaccination is the best protection against getting the flu.

Prescription antiviral drugs may be used to treat the flu in people who are very ill or who are at high risk of flu complications. They’re not a substitute for getting vaccinated. Vaccination is the first line of defense against the flu; antivirals are the second. If you think you’ve caught the flu, you may want to check with your health care provider to see whether antiviral medicine is appropriate for you. Call promptly. The drugs work best if they’re used early in the illness.

To find out more about flu and colds, visit the National Institute of Allergy and Infectious Diseases Web site.

What the Science Says About Complementary Health Approaches for the Flu

No complementary approach has been shown to prevent the flu or relieve flu symptoms.

Complementary approaches that have been studied for the flu include the following. In all instances, there’s not enough evidence to show whether the approach is helpful.

  • American ginseng
  • Chinese herbal medicines
  • Echinacea
  • Elderberry
  • Green tea
  • Oscillococcinum
  • Vitamin C
  • Vitamin D

What the Science Says About Complementary Health Approaches for Colds

The following complementary health approaches have been studied for colds:

Other Complementary Approaches

In addition to the complementary approaches described above, several other approaches have been studied for colds. In all instances, there is insufficient evidence to show whether these approaches help to prevent colds or relieve cold symptoms.

  • Andrographis (Andrographis paniculata)
  • Chinese herbal medicines
  • Green tea
  • Guided imagery
  • Hydrotherapy
  • Vitamin D
  • Vitamin E

NCCIH-Funded Research

NCCIH-supported researchers are conducting a variety of studies relevant to the flu or colds.

Topics of recent research include:

  • Whether probiotics can enhance older adults’ response to flu vaccine
  • Meditation and exercise for preventing acute respiratory infection
  • How psychosocial factors, such as the quantity and quality of social relationships, influence the likelihood of catching colds
  • The effects of echinacea on the immune system.

More to Consider

  • Complementary health approaches should never be used as a substitute for flu vaccination.
  • Tell all your health care providers about any complementary health approaches you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care

For More Information

NCCIH Clearinghouse

The NCCIH Clearinghouse provides information on NCCIH and complementary and integrative health approaches, 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

tty (for deaf and hard-of-hearing callers):

1-866-464-3615

Website: https://nccih.nih.gov/

Email: info@nccih.nih.gov (link sends e-mail)

National Institute of Allergy and Infectious Diseases (NIAID)

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.

Toll-free in the U.S.: 1-866-284-4107

Website: https://www.niaid.nih.gov

Flu.gov

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.

Website: https://www.flu.gov

PubMed®

A service of the National Library of Medicine, PubMed® contains publication information and (in most cases) brief summaries of articles from scientific and medical journals. For guidance from NCCIH on using PubMed, see How To Find Information About Complementary Health Approaches on PubMed.

Website: https://pubmed.ncbi.nlm.nih.gov/

MedlinePlus

To provide resources that help answer health questions, MedlinePlus (a service of the National Library of Medicine) brings together authoritative information from the National Institutes of Health as well as other Government agencies and health-related organizations.

Website: https://www.medlineplus.gov/

Key References

  • Barrett B, Hayney MS, Muller D, et al. Meditation or exercise for preventing acute respiratory infection: a randomized controlled trial. Annals of Internal Medicine. 2012;10(4):337–346.
  • Consumer update: Is rinsing your sinuses safe? U.S. Food and Drug Administration Web site. Accessed at www.fda.gov/ForConsumers/ConsumerUpdates/ucm316375.htm on January 25, 2013.
  • Davidson TM, Smith WM. The Bradford Hill criteria and zinc-induced anosmia: a causality analysis. Archives of Otolaryngology—Head & Neck Surgery. 2010; 136(7):673–676.
  • Hao Q, Dong BR, Wu T, et al. Probiotics for preventing acute upper respiratory tract infections. Cochrane Database of Systematic Reviews. 2015;(2):CD006895. Accessed at www.cochranelibrary.com on January 25, 2016.
  • Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews. 2013;(1):CD000980. Accessed at www.cochranelibrary.com on January 25, 2016.
  • Jiang L, Deng L, Wu T. Chinese medicinal herbs for influenza. Cochrane Database of Systematic Reviews. 2013;(3):CD004559. Accessed at http://www.cochranelibrary.com on January 25, 2016.
  • Karsch-Völk M, Barrett B, Kiefer D, et al. Echinacea for preventing and treating the common cold. Cochrane Database of Systematic Reviews. 2014;(2):CD000530. Accessed at www.cochranelibrary.com on January 25, 2016.
  • King D, Mitchell B, Williams CP, et al. Saline nasal irrigation for acute upper respiratory tract infections. Cochrane Database of Systematic Reviews. 2015;(4):CD006821. Accessed at www.cochranelibrary.com on January 25, 2016.
  • Lissiman E, Bhasale AL, Cohen M. Garlic for the common cold. Cochrane Database of Systematic Reviews. 2014;(11):CD006206. Accessed at www.cochranelibrary.com on January 26, 2016.
  • Oduwole O, Meremikwu MM, Oyo-Ita A, et al. Honey for acute cough in children. Cochrane Database of Systematic Reviews. 2014;(12):CD007094. Accessed at www.cochranelibrary.com on January 26, 2016.
  • Science M, Johnstone J, Roth DE, et al. Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials. CMAJ. 2012;184(10):E551-E561.
  • Seida JK, Durec T, Kuhle S. North American (Panax quinquefolius) and Asian ginseng (Panax ginseng) preparations for prevention of the common cold in healthy adults: a systematic review. Evidence-Based Complementary and Alternative Medicine. 2011;2011;282151.
  • Yoder JS, Straif-Bourgeois S, Roy SL, et al. Primary amebic meningoencephalitis deaths associated with sinus irrigation using contaminated tap water. Clinical Infectious Diseases 2012;55(9):e79–e85.
  • Zhang X, Wu T, Zhang J, et al. Chinese medicinal herbs for the common cold. Cochrane Database of Systematic Reviews. 2007;(1):CD004782 [edited 2010]. Accessed at www.cochranelibrary.com on January 25, 2016.

Acknowledgments

NCCIH thanks John S. Williamson, Ph.D., and David Shurtleff, Ph.D., NCCIH, for their contributions to the 2016 update of this publication, and Bruce Barrett, M.D., Ph.D., University of Wisconsin; Sheldon Cohen, Ph.D., Carnegie Mellon University; and Ronald B. Turner, M.D., University of Virginia School of Medicine for their assistance in the development of the original publication.

This publication is not copyrighted and is in the public domain. Duplication is encouraged.

NCCIH has provided this material for your information. It is not intended to substitute for the medical expertise and advice of your health care provider(s). We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by NCCIH.

Last Updated: November 2016