Apothecaries realised that there were differences in the purity and potency between the substances found in similar species, and that the effects also depended on factors such as the site where they were gathered, or the time of the month or year. Very often scientific discoveries are based on established local use. Romanies, peasants and rainforest tribesmen alike have needed to be accurate botanists for their very survival. These people have understood the healing powers of plants in skilled hands, but they have also appreciated the potential dangers of misuse. Rue was chosen by Mohammed, for example as the most blessed of herbs and it is central to many Arab and Chinese therapies, but it contains a number of active principles which often cause sensitivity to light, and people often develop skin rashes after contact with the plant.
Herbs interact in complex ways with our body chemistry, and their power to heal is formidable.
Compared with synthetic drugs their actions may seem very mild but we should never underestimate the dangers of self-medication on the assumption that herbs are harmless. Many traditional remedies are based on fantasy, guesswork and suggestion, while even the most reputable herbs are selective in their effects, working for one patient but not another. Only a trained practitioner is qualified to diagnose an ailment, and then to suggest a personal prescription after fully assessing your individual needs. The medical benefits of herbs are no longer in doubt, and many are generally quite safe, provided that they are not misused or taken in circumstances where allergic reaction or side effects are possible - even garlic, widely regarded as an infallible panacea, may reduce blood pressure and so cancel the impact of drugs taken for cardiac disorders. All the plants are complex factories producing diverse chemicals, some of them fragranced to attract pollinating insects, others toxins to deter predators, and any one of these substances may be harmful in particular circumstances.