The word aromatherapy is somewhat misleading, as it suggests that it is healing that only works using the sense of smell and on the emotions.

However, aside from the scent, each oil has a combination of constituents that interacts with the chemistry of the body which then affects particular organs or systems as a whole. When oils are used externally as with a massage oil, they are easily absorbed by the skin (at different rates depending on the type of oil) and sent around the body. If you rub a clove of garlic on the sole of the foot, it can be smelled on the breath shortly after.

Essential oils have three modes of action as to how they interact with the human body. Firstly, the pharmacological effect is related to the chemical changes that occur when an oil enters the bloodstream and reacts with hormones and enzymes; secondly, the physiological effect is related to the way that an oil affects the system of the body such as being sedated or stimulated and so on; and thirdly, the psychological effect which happens when an oil is inhaled and causes a response to the smell.

The effect on the mind is probably the most well known but least understood area of aromatherapy. It is known that through history aromatic oils have been used for their power to influence the emotions and mental state, such as with the use of incense in ceremonies.

The olfactory nerve tracts run directly into the limbic system which is the part of the brain connected with memory and motion. This shows that scents can evoke a powerful and immediate response which is not clearly understood. It is also not known to what extent the effect of an oil is dependant upon its chemical or physiological make-up, or to what extent it relies upon a belief or an association.