While the popular herbal remedy echinacea may help shorten the length and severity of cold symptoms, it does not prevent a cold, German researchers report.

"Frankly, I would not actively recommend that consumers take echinacea preparations at the moment," study author Dr. Klaus Linde, of the Center for Complementary Medicine Research, Technical University of Munich, said in a prepared statement.

The findings appear in the current issue of The Cochrane Library.

Echinacea, made from the echinacea purpurea plant, is the top-selling herb in Europe and the United States for the treatment and prevention of colds. In their review, Linde and his team analyzed results from 16 clinical trials. The majority of those studies compared echinacea to a placebo or no treatment. Pressed juices, tablets made from dried extracts, and echinacea suspended in alcohol were the most common forms of the supplement used in the studies.

"There is some evidence that preparations based on the aerial (above-ground) parts of echinacea purpurea might be effective for the early treatment of colds in adults, but results are not fully consistent," the study authors wrote.

They noted there are many different kinds of echinacea preparations on the market. The above-ground parts of the plant and the roots can be used fresh or dried to make tea, squeezed juice, extracts or preparations for external use.

"If someone wants to try echinacea, I would indeed recommend the use, if available, of the products tested positively in clinical trials. If you use other products, you cannot be certain whether they have a similar composition and effect," Linde said.

"Consumers must be aware that ingredients of quality of available products vary greatly -- there might be products which are better than those tested, but we don't know about them," he added.

• More articles on Echinacea

For more information on how to prevent other diseases, use
PreventDisease.com's "Quick Prevention Resources".