When essential oils are breathed in, the molecules rise to the top of the nose. Here they meet the olfactory mucous membrane with its receptors made up of thousands of hairy sensory cells. The receptors identify the smell and the sensory stimulation is passed on through the olfactory bulb. The olfactory bulb is an amplifier and the stimulation passes on through the olfactory nerve and directly into the limbic system of the brain.
The limbic system is the oldest part of our brain. Two important parts of the limbic system are triggered by the nerve impulses, the
Two important parts of the limbic system are triggered by the nerve impulses, the amygdala, and hippocampus. The centers of memory, sexuality, emotional reactions and creativity are found here. While the scent is being compared to a known scent and labeled, pictures and feelings from the past (which can include events, people, places, and objects) are associated with the scent information. As a consequence, we will react emotionally and physically through our autonomous nervous system to an aroma.
In the limbic system, the nerve impulse is led to the hypothalamus. The hypothalamus serves as a switching point for the transmission of aroma messages to other areas of the brain.
The hypothalamus is also the control station for the pituitary. As it receives scent data, it conveys chemical messages to the bloodstream. It is the hypothalamus that activates and releases hormones and regulates body functions.
The thalamus connects the scent information of the limbic system to the area of thinking and judgment. The entire process, from the perception of a smell to the corresponding gland secretion, takes a few seconds. Therefore a simple inhalation of an aroma can cause changes in the body and, depending on the information received, can initiate any number of physiological processes. For example, the immune system could be activated, blood pressure changed, digestion could be stimulated etc. This complex reaction of brain and body takes place every time you smell something. Aroma data received in this manner can cause us to become calm, lively, euphoric, hungry, satiated, sleepy, active, free from pain, etc.
Clary sage has been found to stimulate the thalamus into releasing encephalin, a neurochemical that creates a sense of euphoria and simultaneously gives pain relief.Ylang ylang appears to stimulate the pituitary gland into releasing endorphins, a sexually stimulating neurochemical. While lavender, chamomile or neroli appear to stimulate the release of serotonin, which has a calming effect on fear, stress, aggravation and sleeplessness. Although most of the essential oil molecules which are breathed in are exhaled, some will find their way into the bloodstream via the lungs.
Peter & Kate Damian, Aromatherapy Scent and Psyche, Healing Arts Press, Rochester, Vermont, 1995.
Beverley Hawkins, Aromatherapy 101 Course Notes & Aromatherapy 201 Course Notes, 1999.