Common colds: Does echinacea work?

It is not clear whether echinacea extracts can prevent colds. Taking some echinacea products when a cold starts might help to reduce the cold's length and severity. Because the available products are very different to one another, more research is needed to be sure. Adverse effects are rare.

Echinacea is a plant that is a popular treatment for the common cold. The wide variety of echinacea products available differ in strength and content, depending on which species or part of the plant they use (leaves, roots, flowers or whole plants), how the plant is processed and whether the product includes other ingredients. This means that there is no guarantee that the products that you can buy have the same effect as the few that have been tested in trials.

A group of Cochrane Collaboration researchers reviewed the trials that tested whether echinacea is effective and whether any products are better than others for preventing or treating the common cold.

The researchers found 16 clinical trials comparing echinacea with a fake treatment (a placebo), two comparing it with no treatment, and one trial comparing it with a different type of herbal preparation. Most trials looked at its effectiveness in treating colds, but three looked at whether echinacea could prevent colds.

Good quality trials are needed in order to say whether echinacea really helps to treat colds. People usually recover from colds quite quickly, with or without treatment. This means that it is easy to get a false impression of whether or not cold treatments work.
Although some of the trials were of high quality, they tested so many different types of echinacea treatments that it was difficult to compare them to obtain an overall idea of the plant's relative effectiveness.

There is some evidence that products using the flowers and leaves of one type of echinacea (Echinacea purpurea) might help in the early stages of colds in adults. However, not all of the trials came to the same conclusion so more research is needed to be sure.

Adverse effects of the different echinacea products were rare. If any did arise, they were usually nausea or rashes. In another study, an increase in rashes in children was reported. That may have been caused by an allergic reaction. Although allergies to echinacea are rare, some researchers believe that people who have other allergies or asthma should be aware of the allergy risk when using echinacea.

A lot of people take echinacea products for long periods of time. In Germany, the drug regulatory authority recommends that echinacea not be taken for longer than eight weeks at a time. According to the Cochrane researchers there are no trials on this so far, so it is not clear what the effects of taking echinacea for long periods are.

You can read more about the common cold in our fact sheet.

© IQWiG (Institute for Quality and Efficiency in Health Care)