Some are even dangerous if taken improperly or for extended periods of time. Most problems stem from overuse and misuse. Herbs, when properly used, are safe, gentle and effective. Herbs should be treated like other medicines in that it is important to follow the recommended dosages. Herbs are not under the same strict control as pharmaceutical drugs.
Herbal preparations can vary widely, making the concentration of ingredients often inconsistent.
Toxic impurities have been found in some cases. You should be careful in using herbal products because they are largely unregulated meaning there are no guidelines to ensure dosage, purity or safety of the herbs. Congress passed the Dietary Supplement Health and Education Act of 1994 that limits government control over these products. The act reclassified herbs as dietary supplements which means that herbs are not subject to premarket approval and human clinical trials. If you take herbal supplements, inform your physician of the type and dose to determine whether there is a risk in taking the herb or of an interaction with other medications you may be taking.