Adverse Reactions to Herbal Therapy in Dermatology

R.B. Vender, MD, FRCPC

Dermatrials Research and Faculty of Medicine, McMaster University, Hamilton, Ontario, Canada

ABSTRACT

There are many herbal therapies available for dermatological diseases that patients have already begun to discover. Dermatologists must be educated not only in the benefits of these therapies, but must also be aware of some of the risks and adverse effects. They need information about the effects of herbal remedies in order to better serve their patients who may be using herbs to treat their dermatological conditions. This brief review summarizes some of the more common herbal therapies used by many dermatology patients for their skin diseases, and the adverse reactions and drug interactions that may occur.

Key Words: herbal remedies, adverse effects, dermatology, anti-inflammatory

The use of herbal therapy by dermatology patients is on the rise. Because of their convenient availability, many patients with chronic dermatological diseases have attempted to take more control over their health by using herbal remedies along with or instead of conventional treatments. Some patients have lost hope; standard treatments have failed to be effective for them. As a result, they seek newer therapies in an attempt to find a “cure” for their problems.

Government Regulations

The exact frequency of herbal use is not known because of its non-regulatory status. However, some regulations do exist at the federal level in Canada with the Natural Health Products Directorate (est. 03-99). Most of these regulations are still under review. However, regulations do exist with regard to definitions, product licensing, adverse reaction reporting, site licensing, good manufacturing practices, clinical trials, and labeling/packaging. These are pursuant to the subsection of the Food and Drugs Act entitled Natural Health Products Regulations. Some of these are expected to be phased in over the next two years. At the provincial level, British Columbia established the College of Traditional Chinese Medicine (TCM) Practitioners and Acupuncturists of B.C., becoming the first province in Canada to regulate the practice of TCM.¹ No other province thus far has a similar regulatory body.

There are many herbal remedies that have scientific merit; they may be of clinical benefit and provide safe, effective and reliable alternatives to conventional medicine. However, herbal products cannot be patented.² They are intended for the self-treatment of a self-diagnosed, selflimiting condition. Although there are numerous herbal therapies that are relevant to the specialty of dermatology, many of these have not been studied in proper randomized, double-blind, placebo controlled trials. Most herbal treatments have evidence that is based on sparse anecdotal reports and word of mouth.

Drug Interactions and Side-Effects

Many of these therapies are considered “natural” and therefore harmless. However, because of the poor regulations that exist in monitoring these drugs, adverse reactions do occur.³ Herbal therapy, therefore, should be avoided in pregnancy, infants and children because of the uncertainty of adverse reactions that could occur. There is little incentive for pharmaceutical companies to investigate or standardize these preparations because it is unlikely patents would be applicable.

Because of the assumed safety of natural products, many patients believe these products have “fewer” side-effects. Herbal therapies should be regarded as drugs. Since drugs have side-effects, such events can be seen with herbals. Drug interactions although infrequent, can also occur with herbal therapies and conventional medications.^4,8 This may be due to altered absorption, distribution, biotransformation and/or excretion.⁶ These interactions are often patientinitiated because of the lack of consultation with a physician. These effects can increase or decrease the activity of the corresponding drugs and lead to untoward or unexpected adverse events or changes in drug efficacy.⁵ Some herbals may be contaminated with toxic substances or the herbal can be toxic alone. Others may have traces of potent topical steroids.⁷ This makes it even more important for physicians to take a proper and complete drug history, including herbal medications.

Table 1: A review of some herbal remedies.

Table 2: Side-effects and drug interactions of some herbal remedies

The most common dermatologic reaction from herbal therapies is allergic contact dermatitis.⁸ Herbs that are known for causing this condition include: aloe, arnica, bromelain, calendula, chamomile, goldenseal, tea tree oil and yarrow.^6,4,9 However, more serious events have occurred including erythroderma and Stevens-Johnson syndrome from combination herbal preparations.⁸ Serious systemic adverse events have been reported with herbal therapies for the treatment of dermatological diseases as well.⁷ Most are hepatotoxic effects and some have been fatal although this is rare.⁸ Herbals that are recommended for topical use should not be ingested and vice-versa. Drug interactions that most commonly occur are due to immunomodulatory reactions, however effects on anticonvulsants and anticoagulants can occur.⁵

Conclusion

A brief search of the literature reveals many therapies used for dermatological disease however there are fewer reports of their side effects in dermatologic or medical literature. Only those therapies relevant to the specialty of dermatology that also have had reports of side-effects are discussed. Those therapies without known side-effects are excluded from this manuscript. It is important for dermatologists to become aware of these adverse events and interactions in order to better educate their patients and possibly prevent potential and unexpected adverse reactions.⁸

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