Contact: Diane Relf, Extension Specialist, Environmental Horticulture
Posted April 1997
Never before, even during the heyday of botanic medicine, have laypeople expressed such interest in using herbs to maintain health and to treat disease. They are under the mistaken belief that herbs are healthier and safer than over-the-counter drugs. Nor have so many herbs been so widely available before to those wishing to use them.
Unfortunately, the quality and accuracy of information about the use of such plant materials have not kept pace with the availability. Most packages bear no indications for use, lest the seller run afoul of the Food and Drug Administration. The consumer must refer to popular herbal literature in an attempt to understand the usage, and most of it can only be classified as advocacy literature. In general, the literature is used to sell the product, not to provide sound information based on scientific evidence.
V. E. Tyler of the School of Pharmacy and Pharmacal Science at Purdue and author of "The Honest Herbal" has reviewed some various types of toxins found in herbs. For example, coltsfoot (one of the most popular herbal remedies), comfrey, and borage contain carcinogenic alkaloids. Carcinogenic derivatives are found in wild ginger, betel nuts, sassafras, and calamus. Croton seed and mezerion bark have been linked to tumor promoting compounds.
Arnica, an herb recommended for bruises and sprains may cause contact dermatitis. Angelica, rue, and St. John's wort may induce photosensitivity -- an allergic reaction to light.
Large quantities of Oriental, American, and Siberian ginseng have produced hormone-like effects including post menopausal bleeding. Heliotrine in heliotrope, nicotine in tobacco, and conine in poison hemlock contain alkaloids that induce birth defects. Apricot pits, wild cherry bark, and bitter almonds contain substances that are cellular respiratory inhibitors. Laetrile, which is derived from apricot pits, is not only an unproven cancer cure, but also a toxin belonging to this group.
Use of herbal cathartics and purgatives are risky since it is difficult to measure dosages or predict results. Common cathartics such as aloe, buckthorn berries, and senna; and purgatives such as ipomea and jalap should be avoided. Large quantities of parsley seed, juniper, American and European pennyroyal, tansy, and rue should be avoided as they may cause miscarriages. The oils derived from them should also be shunned. Pennyroyal and peppermint oils contain other volatile oils that can be toxic, respectively, to the liver and lungs. Therjone, derived from wormwood, is highly neurotoxic.
These are only a few of the potentially hazardous herbs commonly used for self-medication. Inclusion here does not mean that single or even repeated doses of the products are going to result in irreparable harm to the user, but it does mean these herbs contain constituents identified to be toxic. The prudent consumer would do well to avoid them.
(Originally published as "Caution: Herbs May Be Hazardous to Your Health," by Elissa Steeves, Extension Technician, Environmental Horticulture, Virginia Tech, in The Virginia Gardener Newsletter, Volume 4, Number 5.)
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