If you are currently being treated with any of the following medications, you should not use echinacea without first talking to your healthcare provider:

Econazole
Echinacea may be useful in combination with econazole, an antifungal agent used to treat yeast infections (such as athlete's foot). When echinacea is used together with econazole, recurrence rates of these infections may be reduced.

Immunosuppressants
Immunosuppressants refers to a group of medications that are used for two main purposes -- treat cancer and suppress the immune system following organ transplant so that the new organ is not rejected. Because echinacea can enhance immune function, it is not advisable to use the herb with medications in this class, especially for organ transplant.

In terms of cancer treatment, however, a couple of test tube studies imply that echinacea may prove useful when used in conjunction with cyclophosphamide, one medication in this class. The idea is that using echinacea with this or other chemotherapy agents that act as immunosuppressants, may allow the cancer-fighting medicines to kill the tumors while the immune system continues to be protected. If this theory proves to be correct, then, echinacea could possibly prevent many of the untoward side effects of chemotherapy.