Homoeopathy is one of the very few systems of natural medicine which may not be entirely compatible with aromatherapy. The reasons for this will be explored a little later.

Homoeopathy is a system for the treatment of illness that is based both on the recognition of patterns within the symptoms of the illness and a wider consideration of how the individual is as a person. Although conventional medical assessment also takes these issues in to account, the homoeopathic approach integrates personality type, previous experiences, emotional state, the influence of the environment and other social factors to a greater degree than is usual with 'standard' medical practice.

Formulated in the first half of the 19th century by Samuel Hahnneman, a German physician, homoeopathy means the treatment of like with like. It depends on the fact that infinitely small amounts of a substance will cure the symptoms that are produced by a larger amount of the same substance. Homoeopathic remedies are prepared by making successive dilutions of animal, vegetable or mineral materials and sometimes bacteria and viruses. As each dilution is further diluted, the mixture is vigorously agitated, or 'succussed', a process which is called potentisalion. Conversely to what might be expected, the more a remedy is diluted, the more powerfully active it becomes. Scientists dismiss homoeopathy because they are unable to detect any measurable trace of the original material in the higher potencies; but yet they are effective, often when more scientifically justifiable treatment has failed.

It seems that homoeopathic remedies work on the level of very subtle vibrational energy and this is why essential oils may be antipathetic to them. Aromatic particles each have their own characteristic rate of vibration, which is involved in the mechanism of smell, but these vibrations are of a less subtle nature than those of homoeopathic remedies, and can negate their action. It has long been known that people taking a homoeopathic medicine should avoid such strong smells as peppermint or eucalyptus, and that the remedies must be stored away from all strong smells. However, homoeopaths are by no means unanimous about the relationship between their art and that of the aromatherapist. Opinions vary from a total ban on the use of essential oils, to a feeling that no harm can be done provided that Eucalyptus, Peppermint and a few other rather powerful oils are avoided. Other suggestions include separating aromatherapy treatment from taking a remedy by at least half an hour, restricting it to some of the gentler oils, such as Camomile and Rose, and that while low potencies are probably not antidoted by essential oils the higher potencies almost certainly are.

The only practical course of action is to make sure that the homoeopath is carefully consulted before using essential oils for anybody who is currently taking a homoeopathic remedy. This would, in any case, be correct professional etiquette. If necessary, massage can be given with a carrier oil only until the course of homoeopathic treatment is finished. Having said that, there are people who use homoeopathic remedies for self treatment and combine them quite happily with aromatherapy, with no apparent detriment to either treatment! Clearly, homoeopathic remedies need to be stored quite separately from essential oils {or any other highly perfumed materials). Keep them in a separate room if possible, or if not, at least in a separate cupboard. One homoeopath suggests that if you use essential oils all the time, any homoeopathic remedies you may have should be replaced at fairly frequent intervals if not used up. Throw them away and replace at least every six months would seem to be a sensible guideline, or buy and use only as needed.

See the entry for Sense of Smell, for a discussion of how vibration relates to smell.