What echinacea is: The leaves, roots or other parts of Echinacea purpurea, Echinacea angustifolia or other species are processed by different methods (drying, alcoholic extraction or pressing) and sold as capsules, tablets, tinctures and tea. Nine kinds of echinacea grow in this country, the most common being Echinacea purpurea. Known as purple coneflower, the plant is part of the daisy (Asteraceae) family, and its extracts have been used medicinally for centuries. It is a complex mix of chemicals, some of which may stimulate the immune system—for better or worse.
Claims, purported benefits: Prevents or reduces the duration and severity of colds; boosts immunity; has anti-inflammatory, antiviral and antibacterial effects. Various species have been extensively studied, but with conflicting results.
What the studies show: Some lab research has suggested that echinacea can stimulate the immune system (or various components of it) and have direct antibacterial/antiviral effects. Human studies on echinacea’s effect on colds or immunity have had inconsistent results. Most commercial preparations in this country have not been tested, and no clinical trials have been done to compare the widely differing preparations.
A meta-analysis from the University of Connecticut made headlines in 2007. It combined the results of 14 older studies and concluded that echinacea can reduce the chances of catching cold and shorten the duration or severity of colds. However, it included some questionable studies as well as many sponsored by the supplement makers. In contrast, some previous reviews, along with many of the better individual studies, have concluded that echinacea has little or no effect on colds. In 2010, for instance, a large study at the University of Wisconsin-Madison, published in the Annals of Internal Medicine, found that echinacea was not better than a placebo at preventing colds or reducing their severity.
In 2011, a study from the University of Wisconsin in Madison, published in Annals of Family Medicine, involved 719 people with early-onset colds who were divided into four groups: standardized echinacea pills (labeled as such), standardized echinacea pills (unlabeled), placebo pills or no pill. All three pill groups, including the placebo group, had slightly shorter and less severe colds than those taking no pills. Those people who said initially that they believed echinacea is effective benefited the most from the pills, whether they contained the herb or placebo.
But in 2012, a large study from Cardiff University in Wales compared a standardized Swiss echinacea extract to a placebo supplement, taken daily for four months. The study found that echinacea reduced the number and severity of colds by about 25 percent.
Side effects: Studies have not shown significant toxicity of echinacea. Nonetheless, echinacea should not be used by pregnant or nursing women or small children. Gastrointestinal upset, headache and rashes have been reported. People who are allergic to daisies, marigolds and other plants in the Asteraceae family should not use it.
Bottom line: It’s still not clear what effect echinacea has on colds and immunity. One problem is that preparations vary widely in the species and plant parts used, though there are some standardized products. Because echinacea may affect the immune system, some experts believe it might worsen autoimmune disorders such as lupus, multiple sclerosis, or rheumatoid arthritis. There are also concerns about echinacea use in people with HIV. The actual risks are unknown, but if you have any of these conditions, you should talk with your doctor before using echinacea, especially long term.