There are conflicting reports as to the appropriateness of this herb in relation HIV and AIDS due to the stimulation of T cell replication and tumor necrosis factor (TNF). Echinacea may support virus replication.

Do not use this herb as a preventative as it unnecessarily stimulates the immune system and provokes a response. Use of this herb should be limited to no more than two weeks at a time. If taken for more than two months, echinacea can cause liver damage.

Do not taken in concert with hepatoxic (potentially liver damaging) drugs such as anabolic steroids, amiodrane, methotrexate, and ketoconazole. High doses of this herb can cause dizziness and nausea in some individuals.

Echinacea should not be used in concert with immunosuppressants such as corticosteroids and cyclosporine.