Essential Oils - Absorption through inhalation

With every breath we take, we receive the most minute pieces of information from our environment.  The Olfactory system carries the fragrance molecules of an essential oil to the Limbic system.  Scents directly influence this area of the brain allowing essential oils to produce feelings, sensations & emotions to reduce pain, arouse, stimulate or relax and to produce a sense of well-being.
(Guide to Aromatherapy-Susanne Blake)