Where an alternative therapy does have an active ingredient (as opposed to touch based therapies or homeopathy) they can easily interact with each other or any conventional medication that is being taken or stop another medicine working. People often don’t disclose use of CAM to their mainstream healthcare provider. Adverse effects and interaction, associated with herbal products and dietary supplements, are not uncommon. Examples include St. John’s Wort, a herb used to treat depression that can also reduce how effective some drugs are. Among these are certain cancer medications, immunosuppressants, and antiretrovirals. Another is Kava kava, a herb often taken to ease anxiety, that can cause liver damage. High dose vitamin C – something often suggested as a complementary treatment during cancer treatment - can affect the effectiveness of chemotherapy and radiation therapies. Some of the herbal products used in Chinese and Ayurvedic Medicine may contain heavy metals, like lead or arsenic.
A proficient alternative therapist would ensure the treatment offered does not interact with orthodox treatment being taken.
[P1] Many alternative medicines can interact negatively with mainstream medicines. [P2] Alternative medicines can be actively harmful.
Rejecting the premises
[Rejecting P2] Alternative medicine is only harmful when taken irresponsibly.