Many people have turned away from conventional medicines, with the belief that
‘natural’ substances like herbs are safer than synthetic substances. This belief is
augmented by many other unwarranted claims such as herbal products do not
contain chemicals while conventional medicines do, thus contributing to the latter’s
side effects. The increasing use of herbal medicines has resulted in concern about
the efficacy and safety of these products. Herbs can be hazardous in many ways.
They may be intrinsically toxic or toxic when taken in combination with other
preparations. Because herbal preparations are usually not evaluated for purity and
consistency of active compounds, they often contain contaminants. Inclusion of
incorrect but toxic species, allergens, pollen, insect parts, heavy metals such as lead,
mercury and arsenic and scheduled poisons (drugs), whether intentional or
unintentional, have been cited as the causes of herbal adverse reactions or toxicities.
The increasing use of herbal medicines means that there is potential for more drug
interactions, particularly between herbal products and conventional ‘Western’
medicines. Toxicity and drug-local herb interaction studies are scarcely conducted
and therefore should be encouraged. Proper documentation of adverse effects of
herbs should be initiated and patients should be asked about their use of herbal
products in order to evaluate the potential of these products to interact with
concurrent prescription medications. The public should be made aware of the
adverse effects of herbal products.