Essential oils are the aromatic, or volatile constituents found in plants. They contain the most active physiological plant properties. Some experts say they contain the life force of the plants. Chemically, essential oils are made up of alcohols, aldehydes, ketones, phenols, terpenes, sesquiterpenes, ethers and esters.
The routes through which essential oils react with the body and its metabolism are called pathways. The most important pathway, in terms of its profound effect of the body, is through the sense of smell. When we smell essential oils, the vapor stimulates small hair-like extensions of our olfactory nerve. The olfactory nerve is the only nerve in the body that is directly contacts the external environment and goes all the way to the brain. All of our other senses (touch, hearing, sight, and taste) involves several nerves and synaptic junctions before the impulses reach the brain. The olfactory nerve stimulates the most primitive part of the brain know as the limbic system, also called the reptilian brain. This is important in the processing of the reaction to emotions, desires, appetites and memories.
In the second phase, essential oils penetrate the epithelial tissues; these include the skin, nasal passages, bronchioles, lungs and gastro-intestinal tract. The essential oils will have a strong effect on these primary contact tissues and pathways. Once absorbed into the surface layer, essential oils quickly penetrate into the lymphatic and blood capillary systems, entering into the general circulation. This is also true for the other epithelial tissues of the body, including sinuses and lungs.
Once the essential oils in the lymph circulatory system it can be carried directly to the liver or fed into the blood stream. As the oil circulates within the blood, body tissues and organs the body may choose any portion of the essential oil that it wishes to utilize in its metabolic process, or simply receive the stimulation, sedation or beneficial property of the oil as it passes through.
The third state of pathways involves the elimination processes of the body. Some components of essential oils are picked up by the surface of the lungs and are out gassed as a vapor. As an example, Eucalyptol (an alcohol in eucalyptus oil) is transported to the lungs surfaces by the blood stream and calms the mucous membranes as it exits. Others, such as terpenes in juniper berry oil, are filtered out by the kidneys, and have stimulating effects on the renal tissue, ureters, bladder and urethra as they exit. Some components of the essential oils are extracted by the liver, held briefly in the gall bladder, and dumped into the GI tract, having profound affects on these organ systems as they pass through. For example Rose oil can stimulate bile production as it is processed by the liver. Some constituents tend to migrate toward the skin, where they will exit via the sebaceous glands and become part of the protective acid mantle. Components of yarrow can increase perspiration as they are excreted.
These direct connection in the pathways are why essential oils can have such a profound and immediate effects on very deep aspects of your being. Research indicates that very small, almost homeopathic qualities create this stimulation. Larger doses do not increase the response appreciably.