ABC of complementary medicine. Homoeopathy.

Homoeopaths treat disease using very low dose preparations administered according to the principle that “like should be cured with like.” Practitioners select a drug that would, if given to a healthy volunteer, cause the presenting symptoms of the patient. For example, the homoeopathic remedy Allium cepa is derived from the common onion. Contact with raw onions typically causes lacrimation, stinging and irritation around the eyes and nose, and clear nasal discharge. Allium cepa might be prescribed to patients with hay fever, especially if both nose and eyes are affected. Other common homoeopathic medicines include those made from plants such as belladonna, arnica, and chamomile; minerals such as mercury and sulphur; animal products such as sepia (squid ink) and lachesis (snake venom); and, more rarely, biochemical substances such as histamine or human growth factor. The remedies are prepared by a process of serial dilution and succussion (vigorous shaking). The more times this process of dilution and succussion is performed, the greater the “potency” of the remedy. Prescribing strategies in homoeopathy vary considerably. In what is often termed “classical” homoeopathy, practitioners attempt to identify the single medicine that corresponds to a patient’s general “constitution”—a complex picture incorporating current illness, medical history, personality, and behaviour. Two patients with identical conventional diagnoses may receive very different homoeopathic medicines. Other practitioners prescribe combinations of medicines (“complex homoeopathy”) or prescribe on the basis of conventional diagnosis alone. There is currently insufficient evidence concerning the relative benefits of the different approaches to treatment.