Herbal supplements, when used as a replacement for conventional medication, can lead to increased symptoms of the illness because of the lack of reliable treatment. Another problem that herbal supplements can bring to people with illnesses is their interactions with medications.
Echinacea, which can suppress the effect of immunosuppressant drugs
Feverfew, which can enhance the effects of aspirin and anticoagulants
Garlic, ginkgo, ginseng, which can increase the risk of
hemorrhages if taken with anticoagulants, or antiplatelet drugs
which can increase the risk of liver damage if taken with acetaminophen, antifungal drugs, methotrexate, or steroids
Valerian, which can enhance drug effects, increase sedation if taken with antidepressants, antiepileptics, anesthetics, analgesics, barbiturates