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Modern science has discovered a lot about how essential oils are absorbed into and interact with our bodies. This section will provide a quick overview of the basic understanding we have of how aromatherapy works.

3.1 The Effects of Scent

In order for us to detect an odor, it must volatize or release molecules into the air where they can be inhaled. Once taken into the nose, the molecules bind with receptors that then fire impulses to the olfactory bulbs located at the base of the brain where the fragrance messages are interpreted and transmitted to the limbic system.

The primary olfactory cortex forms a direct link with several structures (amygdale and hippocampus) of the brain's limbic system. The limbic system commands certain behaviors such as sex drive, sleep cycle, hunger and thirst and is the seat of emotion and feelings. This part of the brain also impacts long-term memory through a structure called the hippocampus that is necessary to the storage of those memories. Scientists divide the brain into three components – the first and oldest being the primitive (or reptilian) brain, the next being the intermediate (or old) mammalian brain and the last being the superior (or new) mammalian brain. While each of these brains is interconnected, they each retain their own particular type of intelligence and functions. So, for instance, the primitive brain, which is most responsible for functions associated with self-preservation, is home to the olfactory system. The limbic system is in the intermediate brain. Higher thought processes—including language, mathematical skills and abstraction—are seated in the superior brain. Because of the direct connection odors have to the limbic system, it's easy to understand why aromatherapy can impact memory and mood as well as behaviors such as appetite and sexual attraction. The structures of the limbic system are also responsible for the release of different neurotransmitters. For example, the pituitary gland releases endorphins, which help alleviate pain and promote a sense of well being. Essential oils have been shown to act on these structures of the brain to promote the production and release of various neurotransmitters which impact the nervous system. Our sense of smell and the impact odors have on us—directly and indirectly—through emotion and memory is a fascinating area of study that is still not wholly understood. Each of us, by paying close attention to our own emotional and physical reactions to various essential oils, can be a pioneer in the exploration of the effects of scent on human beings.

Other than through olfaction, there are a variety of ways in which essential oils can enter the body and impact us, including inhalation, skin, vaginal, rectal and oral.

Inhalation is an easy way for an oil to enter your system and have an impact on your respiratory tract. Once oils enter your respiratory system they then also enter the blood stream where they circulate throughout the body. They will also enter your blood stream directly from your nasal mucosa.

Inhalation can be accomplished via a variety of diffusers including electronic, candle heated, light bulb heated, hot water or simply applying an oil to a surface and breathing it up from that. Even more basic would be to simply breathe it right out of a bottle!

Many studies have been done on essential oils abilities to kill bacteria and fungus. Many oils when airborne have the capability to kill pathogens. More studies have been done on the ability of oils to kill microbes than on any other facet of their possible uses.

Though the tendency might be to think that more is better, the opposite has been shown to be true. Oils need only be breathed in very small amounts. In direct inhalation in a small space, like covering your face to breath in heated steam, one drop should be sufficient for most oils.

Applying oils on the skin is also a popular and effective way to incorporate them into your body. (Always make sure essential oils are properly diluted before skin application.) Even though your skin is a protective layer, oils can be incorporated into your blood system through it. One interesting study with lavender oil, applied via a stomach massage, showed that its key constituents were measurable in the blood within 20 minutes, and they stayed in the blood system for up to 90 minutes. Their ability to circulate throughout your body systems makes essential oils especially effective and efficient.

Some parts of your body absorb oils better than others. The best areas include your armpits, mucous membranes, soles and palms, genitals and any area where you have a small amount of hair. Following a hair follicle is the quickest way for an oil to penetrate the skin. (While the underarms and genitals are very efficient application points for absorption, care should be taken because of the sensitivity of these areas.)

Factors that can easily improve your ability to absorb oils via the skin include moisture, body temperature, the use of surfactants like soap, covering the skin with cloth after oil application and the use of easily absorbed carrier oils. Baths are great for essential oil application as they allow you to breathe in the oils, your body temperature goes up and your skin moisture level goes up. Exercise also raises body temperature and skin moisture and thus enhances absorption. A warm room is much more conducive to absorption than a cold room.

Though not common in the United States essential oils are sometimes absorbed vaginally and rectally. Some companies in the U.S. and many in Europe sell essential oil suppositories. (One of the most common is tea tree oil.) Because these oils are absorbed more rapidly and in much higher levels than in other methods, and the areas are so sensitive, we don't recommend this method of application.

Oral administration is more commonly practiced in Europe than in the U.S. We also do not recommend oral consumption. Virtually all serious cases of essential oil poisoning occurred from oral consumption. Even small amounts of some oils can be dangerous, and they can irritate the gastrointestinal tract. Some oils have constituents that must be processed via the liver and the end result may be damage to the liver.

It should be noted that many oils can be safely gargled (if properly diluted) or otherwise used for oral hygiene if not swallowed especially oils used on the gums for antibacterial or local anesthetic like clove bud and tea tree oil.

When oils are absorbed into the body, the body must then eliminate them. Oils are eliminated via the kidney, liver, skin or lungs. (Often it is possible, after applying an essential oil to the soles of your feet, to then smell the oil on your breath or as you perspire.)

Review Questions Section 3

1. Describe the process of olfaction.

2. What is the limbic system and why does it play such an important role in aromatherapy?

3. What ways other than olfaction, can essential oils enter the body?

4. Why is it best not to ingest essential oils?

5. How are essential oils eliminated from the body?

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