Smell is a specialised chemical sense. It is interesting to note that the olfactory cells are the only place in the human body where the central nervous system is in direct contact with the external environment. When we detect the smell of something, there is a direct contact between the molecules of scent and our own receptors.

The message regarding the molecule of scent is passed along the olfactory nerve to the nerve centre in the brain. The neurons of the olfactory nerve, control the inner responses, i.e. emotions and memories, as well as the body’s hormones. There is no generally accepted classification of the basic types of smells recognized by man. The sense of smell can be very sensitive, sensing minute concentrations of some substances in the air.

There is considerable individual variation in the activity of the sense of smell. Adaption can occur to pleasant as well as nasty smells, due to changes in both the receptors and the central connections.

It is important to remember that the inhalation of the aromas of essential oils also has a profound and instantaneous effect on us today. The limbic lobe of the brain receives information about smell via the olfactory nerve and this part of the brain is also concerned with our emotional memory. The limbic system produces the autonomic responses that accompany emotional states and behaviours.

Particular scents can trigger strong, emotional responses which are pleasant or unpleasant according to our own individual experience. Which smells do you find repellent? What are your favourite scents? Perhaps the perfume of a favourite blossom or newly-mown grass, the scents of the garden after light summer rain, the smell of your favourite meal cooking or the perfume worn by a friend, the special scent of a baby or small child.

When oils are inhaled, micro-molecules of essential oils travel through the nasal passages to the limbic system of the brain which is the seat of memory and emotion.

The breathing in of essential oils is thought to trigger memories and emotions within the limbic system, which in turn stimulates a response within the entire system.

With the memory comes instant recall of the associated emotion – pleasure, happiness, laughter, affection or perhaps sadness, pain, grief.

For this reason, it is important to always heed the emotional responses to the aroma of the essential oils you intend to use. If the scent is in any way repellent, then it is wise to adjust your choice of oils for your blend. The subconscious, emotional responses are telling you something of vital importance and you would be wise to listen. Otherwise, you severely curtail the degree of benefit given.

Smell takes a direct, physical route to the brain because they employ nerve cells as transmitters and receivers. Odours travel directly through the olfactory system in the nose and the front part of the head into the limbic area of the brain which processes the smell.