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Safety Issues

The question of possible side effects and toxicity has arisen more lately as herbs are increasingly under the scrutiny of the scientific eye. However, adverse reactions to herbal medicines seldom occur in practice, and those that do occur generally consist of mild rashes or bowel changes. A herbal practitioner would not normally expect a “healing crisis” with an exacerbation of symptoms before they start to recede.

There are two main sources of information about the efficacy and the safety of herbal medicines – ancient folklore and modern science. The empirical evidence gathered by herbalists over thousands of years, which is now being increasingly justified by scientific research, means that patients may be assured that their herbal prescriptions are based on reliable foundations. Many herbs form the basis of modern orthodox medicines, and it may be surprising to learn that the pharmaceutical industry harvests huge plantations of herbs for use in the production of drugs each year. It also grows herbs for further research activities.

The use of whole plant medicines, as opposed to isolated active ingredients, helps to prevent adverse side effects. The many types of substances in medicinal plants work synergistically together, and probably all have important roles to play in the healing process. The primary healing agents are the active constituents that were isolated by the early chemists and developed into modern drugs, but the importance of the other apparently secondary constituents should not be ignored, since they are vital for determining the efficacy of the primary healing agents. Some secondary synergistic substances make the active constituents more easily assimilated and available in the body, while others will buffer the action of other potent plant chemicals, preventing possible side effects. It is largely the combination of both types of substances occurring in the whole plant that determines the potency and safety of herbal medicine.

Potential Adverse Reactions

Having said this, with the huge range of biochemical constituents that occur in herbs it is possible that, though generally safe, some could potentially cause allergic reactions and idiosyncratic responses in the same way that foods do. Most of these can be avoided by herbalists who are generally familiar with the chemistry of herbs they are prescribing and only prescribe herbs which are formulated to suit the specific needs of the patient in appropriate doses only after taking a detailed case history. Certain people are more likely to have hypersensitive reactions to herbs than others, particularly those who already have a history of food allergy or intolerance or chemical sensitivity. This is more likely if they suffer from digestive problems, specifically imbalances in the intestinal flora and leaky gut syndrome, which actually lend themselves very well to herbal treatment.

The risk of adulteration of herbs supplied to herbalists is one that is obviously a concern. Adverse effects have occurred on occasions due to adulteration with toxic herbs, as well as bad labelling. When buying herbs, it is vital that their sources are known, reputable and preferably organic, since adverse reactions to pesticides and preservatives are hard to quantify and could be confused with reactions to a plant itself. Indian and Chinese herbs are considered more of a safety problem than European herbs, although the use of pesticides in Eastern Europe has also attracted negative attention.

Herb/Drug Interactions

This is a relatively new science but available information on the subject (much of which may be speculative rather than empirical) is growing all the time. Although herbs have been taken for thousands of years, they have only been used in combination with nutritional supplements and allopathic drugs on a widespread basis for approximately the last forty years or so. The concern is not so much that the reaction between a herb and a drug is toxic, rather that it is possible that certain herbs can affect the bioavailability of drugs and nutrients, and cause an increase or decrease in levels of drugs in the blood. This is important to know, especially if patients are taking specific doses of powerful drugs such as cardiac medication, anti-clotting agents or they may need to have surgery.

Herbs high in mucilage or fibre, such as slippery elm or psyllium seeds, or herbs rich in tannins which might bind up drugs in the intestines, may inhibit absorption. Warming digestive herbs such as cayenne, long and black pepper can increase absorption of medicines, while herbs that act on liver enzyme systems may affect the break down of certain drugs and inhibit their elimination, effectively raising the drug dosage which could cause side effects. Care needs to be taken with insulin-dependent diabetics as certain herbs lower blood sugar. Interestingly in China, where the herbal tradition has remained unbroken and there is less suspicion about herbs than there is in the West, herbs are often combined with drugs for intentional effects, either to reduce side effects of drugs or to enhance their effects.

Filipendula, or meadowsweet, is rich in tannins, which may inhibit the absorption of some drugs.