Aromatherapy and the Brain: Part 1

Image from Honolulu Media

The use of aromatherapy as a treatment for various ailments may seem like a “new age” invention, but in reality, “Essential oils have been used for therapeutic purposes for nearly 6,000 years. The ancient Chinese, Indians, Egyptians, Greeks, and Romans used them in cosmetics, perfumes, and drugs.” The term “aromatherapy” refers to the “use of essential oils from plants for healing. Although the word ‘aroma’ makes it sound as if the oils are inhaled, they can also be massaged into the skin or — rarely — taken by mouth.” A mounting body of evidence suggests that those ancient civilizations may have been onto something.

It is still unclear if essential oils exert a legitimate therapeutic effect, but one thing is for certain: odors do activate different parts of the brain. According to the National Cancer Institute (PDQ), “Studies have consistently shown that odors can produce specific effects on human neuropsychological and autonomic function and that odors can influence mood, perceived health, and arousal. These studies suggest that odors may have therapeutic applications in the context of stressful and adverse psychological conditions.” One possible mechanism that could explain the mood-altering effects of inhaling essential oils is the connection between the limbic system and the amygdala. Cynthia Deng explains, “When you smell lemon oil, some molecules dissolve in the mucus lining of the olfactory epithelium on the roof of the nasal cavity. There, the molecules stimulate olfactory receptors. Olfactory sensory neurons carry the signals from the receptors to the olfactory bulb, which filters and begins processing the input signals of the lemon scent. Mitral cells then carry the output signals from the olfactory bulb to the olfactory cortex, which allows you to perceive and recognize the tangy scent of lemon. Interestingly, the mitral cells do not only lead to the olfactory cortex, they also carry the signals from the lemon scent to other areas in the brain’s limbic system. Some mitral cells connect directly to the amygdala, the brain structure involved in emotional learning and memory.”

Furthermore, olfactory receptors are found in and around the entire human body, not just in the nose. In fact, “More than 150 olfactory receptors have been identified outside the nose and are currently an active area of study.” One recent study observed the olfactory response in skin: “The researchers found that Sandalore, a synthetic sandalwood oil used in aromatherapy, perfumes, and skin care products all bound to the receptor, triggering cells to divide and migrate, processes characteristic of skin healing.” Also of note is the fact that, “A therapeutic-grade essential oil can increase cellular oxygen up to 21 percent – no other plant component comes close.” While we can’t say for sure how these factors contribute to the brain’s response, it’s clear that at the very least, the brain responds. From here, we can further investigate potential therapeutic implications.

This is part one of a two part series on aromatherapy. Join us next week when we discuss the current research on specific oils, as well as side effects and research limitations.

-Written by Betty Vine

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