Summary : We performed a systematic review of controlled clinical trials to check the evidence for the immunomodulatory efficacy of preparations containing extracts of Echinacea. Trials were searched by on-line searches in Medline and Embase, a search in the private database Phytodok, contacts with researchers and drug companies, and by checking references in available articles.
All available historically and prospectively controlled trials investigating the prophylactic or therapeutic immunomodulatory activity of preparations of Ecbinacea alone or in combination with other plant extracts or homeopathic dilutions in humans were included. Study characteristics, results, and conclusions of primary authors were analyzed using standardized evaluation forms and methodological quality assessment using a predefined score system.
A total of 26 controlled clinical trials (18 randomized, 11 double-blind) were identified; 6 of these involved testing three different mono-extracts, and 20 involved testing three different preparations also containing other ingredients. Nineteen trials studied the efficacy of the prophylactic or curative treatment of infections; 4 trials the reduction of side-effects of antineoplastic therapies and 3 trials the modulation of various laboratory immune parameters. The primary authors claimed that 30 of the 34 treatment strategies showed a superior efficacy to those of the control groups. The methodological quality of most studies was low and only 8 trials scored more than half of the maximum possible score points.
Existing controlled clinical trials indicate that preparations containing extracts of Echinacea can be efficacious immunomodulators. However, the evidence is still insufficient for clear therapeutic recommendations as to which preparation to use and which dose to employ for a specific indication. Further methodologically sound, randomized clinical trials should be conducted.
Keyword : systematic review, randomized clinical trials, clinical trials, immunomodulation, medicinal plants, Echinacea
Immunomodulation with Echinacea - a systematic review of controlled clinical trials - D. Melchart, K. Linde, F. Worku, R. Bauer, H. Wagner - Phytomedicine Vol. 1/1994, pp. 245-254

Abstract : A number of immunomodulatory effects have been attributed to the medicinal plants Echinacea angustifolia and Goldenseal (Hydrastis canadensis); however, little is known about whether treatment with these plants can enhance antigen-specific immunity. We investigated the antigen-specific in vivo immunomodulatory potential of continuous treatment with Echinacea and Goldenseal root extract over a period of 6 weeks using rats that were injected with the novel antigen keyhole limpet hemocyanin (KLH) and re-exposed to KLH after the initial exposure. Immunoglobulin production was monitored via ELISA continuously over a period of 6 weeks. The Echinacea-treated group showed a significant augmentation of their primary and secondary IgG response to the antigen, whereas the Goldenseal-treated group showed an increase in the primary IgM response during the first 2 weeks of treatment. Our results suggest that medicinal plants like Echinacea or Goldenseal may enhance immune function by increasing antigen-specific immunoglobulin production.
Keywords : Antibody production; Echinacea angustifolia; Goldenseal; Hydrastis canadensis; Immunomodulation; Immunostimulation; KLH
Increased production of antigen-specific immunoglobulins G and M following in vivo treatment with the medicinal plants Echinacea angustifolia and Hydrastis canadensis - Jalees Rehman, Jennifer M. Dillow, Steve M. Carter, James Chou, Brian Le, Alan S. Maisel - Immunology Letters 68 (1999) 391–395