What it 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.
Intended uses: 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 science says: Some lab research has suggested that echinacea can stimulate the immune system (or various components of it) and have direct antibacterial/anti-viral 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.
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.
In 2014 a research review by the Cochrane Collaboration looked at 24 clinical trials. In individual trials, echinacea did not prevent colds, but a meta-analysis combining the studies did suggest that the herb might have a small effect on cold incidence. In treatment trials, echinacea did not shorten duration of colds.
A meta-analysis in Advances in Therapy in 2015, which included six clinical trials, found that echinacea reduced the risk of recurrent respiratory tract infections by about a third, as well as reducing their complications.
Also in 2015, a Czech clinical trial in Current Therapeutic Research found that a standardized extract of echinacea herb and root (along with elderberry) was as effective as oseltamivir (Tamiflu) in treating 473 people with early symptoms of the flu.
Common side effects: Studies have not shown significant toxicity of echinacea. Nonetheless, echinacea should not be used by people taking immunosuppressive drugs. 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.
Our advice: 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.