Echinacea is one of the most popular herbal remedies used today for the common cold. Echinacea is purported to aid in the treatment or prevention of upper respiratory tract infections. Clinical trial data, recently appearing in an issue of Annals of Internal Medicine, raised questions concerning its efficacy. Investigators at the University of Wisconsin assessed efficacy of dried, encapsulated, whole plant echinacea, for early treatment of symptoms associated with the common cold. The study group consisted of 150 students experiencing symptoms depicting the onset of the common cold.
In a double-blinded, randomized trial, half the group received an encapsulated mixture of unrefined Echinacea purpurea herb (25 per cent), root (25 per cent) and E. augustifolia root (50 per cent). They were exposed to 1g doses six times during the first day of illness and three times on each subsequent day of illness for the duration of 10 days. The other half of the study group received a placebo. The severity of symptoms over time was nearly identical in both study groups. This group of investigators concluded that echinacea provided no detectable benefit, or harm, in the study participants.
However, it may be noted that earlier studies have shown positive effects from the herb. The failure to show effect in the recent study may be due to a huge variation of different blends and concentrations available on the market. There exist 200 different forms of echinacea sold worldwide, from teas to capsules, but few have been tested. The plant chemicals vary among botanical species. Contributing factors such as growing conditions, plant part and method of extraction can also affect efficacy. Thus, it is possible that one preparation may be beneficial while another may appear to have no effect.