Always consult a healthcare provider before using herbal products, as they can cause serious side effects and interact dangerously with prescription medications. The U.S. Food and Drug Administration (FDA) classifies herbal products as dietary supplements, meaning they do not undergo the same strict pre-market testing for safety and efficacy as prescription drugs. Many common herbs can change how prescription medicines work. For example, St. John's wort can dangerously reduce the effectiveness of birth control pills, heart medications, and antidepressants. Many herbs can stimulate uterine contractions, cross the placenta, or pass into breast milk, posing hidden risks to a developing fetus or infant.