Many people try herbal supplements containing echinacea to combat the common cold. According to a 2007 national survey, echinacea ranked third in herbal supplement use by adults and first in supplement use by children. Researchers have been investigating this widely used herb to see whether it is effective in preventing or treating colds. Three NCCIH-funded studies that compared echinacea with placebo did not find a benefit.
In one study, published in The New England Journal of Medicine, researchers at the University of Virginia School of Medicine examined Echinacea angustifolia root extracts for effects against rhinovirus (a virus that causes the common cold). The researchers compared three echinacea preparations in tincture form, each with different phytochemical properties. Participants—399 healthy young adults—received placebo or echinacea (300 mg three times daily), beginning 7 days before exposure to rhinovirus. None of the echinacea preparations in this study reduced the rate of infection, severity of symptoms, or inflammation.
In another study, published in Annals of Internal Medicine, researchers at the University of Wisconsin-Madison evaluated the effects of unrefined echinacea (capsules combining E. angustifolia root and Echinacea purpurea whole plant) on cold symptoms. Participants—142 college students with early symptoms of a cold—received placebo or echinacea (1 g six times on the first day and then three times daily, for up to 10 days). Echinacea did not reduce the severity or duration of symptoms in this study.
In a third study, published in the Journal of the American Medical Association, researchers from the University of Washington Child Health Institute evaluated echinacea for efficacy and safety in children with upper respiratory tract infections. The preparation was a syrup containing dried, pressed E. purpurea juice from the above-ground parts of the plant. Participants received either placebo or echinacea (3.75 mL twice daily for children ages 2 to 5; 5 mL twice daily for children ages 6 to 11). Analysis of data from upper respiratory tract infections in 407 children in this study found that echinacea did not reduce the severity or duration of symptoms and was associated with increased risk of rash.
Overall, results of echinacea research have been mixed. Some studies have found benefits; others, such as those described above, have not. Challenges associated with conducting this research include identifying the most effective parts of the echinacea plant, evaluating differences among echinacea species, and determining proper doses and preparations.
Barrett BP, Brown RL, Locken K, et al. Treatment of the common cold with unrefined echinacea: a randomized, double-blind, placebo-controlled trial. Annals of Internal Medicine.;137(12):939–946.2002
Taylor JA, Weber W, Standish L, et al. Efficacy and safety of echinacea in treating upper respiratory tract infections in children: a randomized controlled trial. Journal of the American Medical Association.;290(21):2824–2830.2003
Turner RB, Bauer R, Woelkart K, et al.. An evaluation of Echinacea angustifolia in experimental rhinovirus infections.. The New England Journal of Medicine. .;;353(4):341–348..2005