But if you are already taking St John's wort with medication, don't stop without seeking your GP's advice, because the dose of your medicine may need to be changed. Many women take this popular herb to relieve premenstrual symptoms. For others, it soothes the maddening itch of eczema. The current lack of regulation has allowed sub-standard, often contaminated herbs to be imported from China, India and Africa. As the use of Chinese medicine soars, there are some 500 different species of Chinese herb available here.
Problems arise when practitioners unknowingly give patients the wrong herb or dose.
In July 1999, all species of the Chinese herb Aristolochia were banned after it was mistakenly used to treat eczema, instead of a harmless lookalike herb, Clematis. One herbal drug which has been adulterated is Tian Ma, used to treat high blood pressure and headaches. In one batch, dried dahlia tubers had been substituted for the herb Gastrodia elata. However, when used in conjunction with warfarin, it can cause bleeding, thus presenting a serious risk for coronary heart disease patients. Without informing her doctors, she took ginkgo biloba along with her prescribed drugs and suffered a brain haemorrhage.