The ability of essential oils to affect our brain waves, emotions, physiology, memory and
other functions has to do with how our body processes scents.

The ability to smell is perhaps the most fascinating of our senses. Humans can
distinguish between 2000 and 4000 different odors, depending upon the individual. It is
the most immediate of our senses and in terms of evolution, perhaps the most important.
Early man’s survival in the wild was greatly aided by his ability to smell predator or prey
before he could see or hear it. At this early point of evolution, smell would have been a
most important sense for survival. In our modern times most of us have lost that
acuteness of the nose. The sense of sight has now surpassed all of the others as our
most important form of sensory awareness.

The sense of smell is the only one of our senses that is wired directly into the brain so that
the result is immediate. The brain must interpret the other senses before they can be
comprehended. The olfactory nerves have been described as "brain cells outside the
brain." The olfactory bulbs lie in the upper part of the nose. These nerves are then
connected directly to the limbic system.

The inside of the nose is moist and the moisture dissolves particles of aromatic vapor.
The olfactory nerves can only detect aromatic particles when they are in this liquid form.
Each olfactory cell has several fine filaments coming from it that are called cilia. The tips of
these cilia have receptor shapes that fit with the dissolved molecules of scent.

The scent information is then transmitted from these cilia to longer nerve cell fibers and is
taken directly to the limbic system of the brain. The limbic system is called the visceral or
emotional brain, also the old brain or reptilian brain. It is the part of the brain that was
developed first before speech and tools, the survival part of ourselves. It registers
emotions, pleasure, pain, fear, anger, sorrow and sexual feeling; it controls the involuntary
aspects of ourselves. The limbic system has nerve pathways to the hypothalamus and the
autonomic nervous system. The hypothalamus controls the endocrine system that
secretes the hormones that effect growth, sex, metabolism, etc. The autonomic nervous
system controls unconscious activities such as digestion, rate of heartbeat, body
temperature and hunger. Scents have far reaching effects upon the body.

Smell is innate. It is an unconscious activity that has enormous effect on our physiology.
Another attribute of scent is that it is strongly connected to memory. If you have a horrible
memory of your third grade teacher who always smelled of lavender, you would probably
not find lavender soothing and balancing as most people do. You may forever associate
that scent with unpleasantness. The same phenomenon is experienced in smelling a
scent connected to a loved one. A whiff of a perfume can bring back memories of the most
romantic night of your life.

There are some other interesting phenomena with smell. Saturation and fading is when
we are exposed to one smell for a long time. It disappears from our conscious
awareness. The most obvious is the cook who cannot smell the food cooking until she
leaves and comes back into the kitchen. Tiring is when we are exposed to a succession of
smells within a short time. If you smell essential oils you can only clearly smell about
three or four before they all start to smell similar. Sniffing coffee beans is said to help clear
the nasal pallet if you are smelling quite a number of scents.

Our ancestors recognized what science is now proving, that scents can effect your
emotions and your brain waves. Studies have shown that scents inhaled effect pulse rate,
blood circulation and breathing. Other studies have shown brain wave changes, sedating
or stimulating, depending on the scent. Scents like lavender, bergamot, marjoram,
sandalwood, lemon and chamomile are found to be calming and sedating. Stimulating
fragrances include peppermint, clove, basil and rosemary.
The Anatomy of Smell
http://www.juniperandsage.com/oils/anatomy-of-smell.php