This area is perhaps the most discussed and yet least understood area of activity regarding essential oils. There is no doubt that throughout history aromatic oils have been used for their power to influence the emotions and states of mind: this is the basis for their employment as incense for religious and ritualistic purposes. It is already known that two olfactory nerve tracts run right into the limbic system (the part of the brain concerned with memory and motion), which means that scents can evoke an immediate and powerful response that defies rational analysis.

Recent research at Warwick University, England, and Toho University, Japan, has aimed to put these traditionally held beliefs and applications into a scientific context. They came up with two types of reactions to odours which they called a 'hard-wired' response or a 'soft-wired' response; the first type is ingrained from before birth and is purely instinctual; the second is learned or acquired later on.

But to what extent is the effect of a particular oil dependent upon its chemical or physiological make-up, and to what extent does it rely upon a belief or an association? In dealing with the psychological or emotional responses to the scent of a particular oil, this kind of classification becomes much more difficult: surely here it is more appropriate to consider the temperament of each individual within a given context, rather than predict a set reaction.

At the Psychology of Perfumery Conference 1991, it was generally agreed that 'while pharmacological effects may be very similar from one person to another, psychological effects are bound to be different'. The effect of an odour on a human being was dependent an a variety af factors, which include:

1. how the odour was applied
2. how much was applied
3. the circumstances in which it was applied
4. the person to which it was applied (age, sex, personality type)
5. what mood they were in to start with
6. what previous associations they may have with the odour
7. anosmia, or inability to smell (certain smells).

When we begin to consider individual needs, essential oils start to demonstrate the versatility of their nature. The rose is a good example: a flower associated with beauty, love, and spiritual depth in folklore and religious texts, but also with a long tradition of usage for physical conditions such as skin problems, regulating the female cycle, promoting the circulation, purifying the blood and as a heart tonic. When we smell the fragrance of the rose, it carries all these rich associations with it, affecting our mind and body simultaneously, as the effect is moulded by personal experience.

'The general trend of modern thought is strictly dualistic; psychic and somatic happenings are treated as mutually exclusive rather then inclusive.' Trying to disentangle spirit from matter leads nowhere; as David Hoffmann says, 'Mind and Matter are mutually enfolded projections of a higher reality which is neither matter nor consciousness.'