Recurrent erythema nodosum associated with Echinacea herbal therapy.

We report a case of recurrent erythema nodosum that is temporally and perhaps causally associated with use of echinacea herbal therapy. The genus Echinacea is traditionally used as an immunostimulant in the prophylaxis and treatment of upper respiratory tract infections. In vitro and in vivo studies of echinacea administration in animal and human-derived models suggest a definite stimulatory effect on the cellular immune system, although the clinical impact of echinacea is still unknown. The public's increasing use of alternative and complementary therapies necessitates that dermatologists be familiar with the cutaneous adverse effects of these agents.