Aromatherapy Research: Essential Oils Change Brainwaves When Inhaled Digging through the research on the National Institutes of Health website, Pub Med (see http://www.ncbi.nlm.nih.gov/pubmed/) can really be fruitful for scientific data on the effects of essential oils.
A great many studies have been published over the last ten years validating the use of essential oils in many realms of natural health, from immunity and infectious illness to wound healing and pain relief, to sleep, mood and cognitive effects. Here are a few studies noting measurable changes in brainwaves upon inhalation of aromas. Now it’s not surprising that essential oils elicit changes in brainwaves – really this happens with anything we perceive with our sense organs: touch, sight, hearing, taste OR smell. What’s interesting is that the brainwaves are in-fact measurably different depending on the oil inhaled.
Further, the brainwave response was also dependent on the time of day and type of action the subjects were performing when inhaling the oils. Some oils seemed appreciated during physical work, some during mental work, some before work and some after. The first study describes changes in Alpha brainwaves. These waves are associated with a relaxed, steady, perhaps even ‘contemplative’ state (one website described most of America as ‘alpha wave challenged’!) Lavender essential oil produced the most significant, fairly rapid increase in Alpha wave activity.
The second study describes differences between oils which may be considered relaxing, uplifting or mentally stimulating before and after both physical and mental work. Some oils tested produced very statistically significant results: In summary, try Orange before physical work and Cypress after. Try Basil before mental work and Juniper afterward. Study: Effects of inhalation of essential oils on EEG activity and sensory evaluation. Masago R, Matsuda T, Kikuchi Y, Miyazaki Y, Iwanaga K, Harada H, Katsuura T. Graduate School of Science and Technology, Chiba University. The purpose of this study was to investigate EEG changes in subjects directly after inhalation of essential oils, and subsequently, to observe any effect on subjective evaluations.
EEG and sensory evaluation were assessed in 13 healthy female subjects in four odor conditions. Four odor conditions (including lavender, chamomile, sandalwood and eugenol) were applied respectively for each subject in the experiment. The results were as follows. 1) Four basic factors were extracted from 22 adjective pairs by factor analysis of the sensory evaluation. The first factor was “comfortable feeling”, the second “cheerful feeling”, the third “natural feeling” and the fourth “feminine feeling”.
In the score of the first factor (comfortable feeling), the odors in order of high contribution are lavender, eugenol, chamomile and sandalwood. 2) Alpha 1 (8-10 Hz) of EEG at parietal and posterior temporal regions significantly decreased soon after the onset of inhalation of lavender oil. The change after inhalation of sandalwood was not significant. These results showed that alpha 1 activity significantly decreased under odor conditions in which subjects felt comfortable, and showed no significant change under odor conditions in which subjects felt uncomfortable. These results suggest a possible correlation between alpha 1 activity and subjective evaluation.
Study: Alteration of perceived fragrance of essential oils in relation to type of work: a simple screening test for efficacy of aroma. Sugawara Y, Hino Y, Kawasaki M, Hara C, Tamura K, Sugimoto N, Yamanishi Y, Miyauchi M, Masujima T, Aoki T. Department of Health Science, Hiroshima Prefectural Women’s University, Japan. The perceptional change of fragrance of essential oils is described in relation to type of work, i.e. mental work, physical work and hearing environmental (natural) sounds. The essential oils examined in this study were ylang ylang, orange, geranium, cypress, bergamot, spearmint and juniper. In evaluating change in perception of a given aroma, a sensory test was employed in which the perception of fragrance was assessed by 13 contrasting pairs of adjectives. Scores were recorded after inhaling a fragrance before and after each type of work, and the statistical significance of the change of score for 13 impression descriptors was examined by Student’s t-test for each type of work.
It was confirmed that inhalation of essential oil caused a different subjective perception of fragrance depending on the type of work. For example, inhalation of cypress after physical work produced a much more favorable impression than before work, in contrast to orange, which produced an unfavorable impression after physical work when compared with that before work. For mental work, inhalation of juniper seemed to create a favorable impression after work, whereas geranium and orange both produced an unfavorable impression then.
From these studies, together with those conducted previously with lavender, rosemary, linalool, peppermint, marjoram, cardamom, sandalwood, basil and lime, we thus concluded that the sensory test described here might serve not only as a screening test for efficacy of aroma but also as a categorized table for aroma samples which can act as a reference to each other.
Because the limbic system is directly connected to the parts of the brain that control heart rate, blood pressure, breathing, memory, stress levels, and hormone balance, therapeutic-grade essential oils can have profound physiological and psychological effects. The sense of smell is the only one of the five senses directly linked to the limbic lobe of the brain, our emotional control center.
Scent stimulates nerves to fire in the emotional center of the brain, but it also stimulates the master gland to release hormones. Hormones affect the fight/flight response, as well as digestion and heart rate. In this way, essential oils can affect us in many ways all at once, just through their fragrance. Anxiety, depression, fear, anger, and joy all emanate from this region. The scent of a special fragrance can evoke memories and emotions before we are even consciously aware of it. When smells are concerned, we react first and think later. All other senses (touch, taste, hearing, and sight) are routed through the thalamus, which acts as the switchboard for the brain, passing stimuli onto the cerebral cortex (the conscious thought center) and other parts of the brain. The limbic lobe (a group of brain structures that includes the hippocampus and amygdala located below the cerebral cortex) can also directly activate the hypothalamus.
The hypothalamus is one of the most important parts of the brain, acting as our hormonal control center. It releases chemical messengers that can affect everything from sex drive to energy levels. The production of growth hormones, sex hormones, thyroid hormones, and neurotransmitters such as serotonin, are all governed by the hypothalamus. Thus, the hypothalamus is referred to as the “master gland.” Essential oils–through their fragrance and unique molecular structure–can directly stimulate the limbic lobe and the hypothalamus. Not only can the inhalation of essential oils be used to combat stress and emotional trauma, but it can also stimulate the production of hormones from the hypothalamus.
This results in increased thyroid hormones (our energy hormone) and growth hormones (our youth and longevity hormone). A therapeutic-grade essential oil can increase cellular oxygen up to 21 percent – no other plant component comes close. For instance, hydrogen peroxide increases cellular oxygen only 9%. Bacteria and viruses cannot live in a negative ion environment. And, there has never been an instance of any bacteria or virus developing resistance to or mutating in the presence of a high quality essential oil – without doubt the reason being due to the extremely complex compounds. In a large clinical study , Alan Hirsch, MD, tested the fragrances of peppermint, to trigger significant weight losses in a large group of patients who had previously been unsuccessful in weight-management programs. During the course of the six-month study involving over 3,000 people, the average weight loss exceeded 30 pounds. According to Dr. Hirsch, some patients actually had to be dropped from the study to avoid becoming underweight.
Another double blind, randomized study by Hirsch  documented the ability of aroma to enhance libido and sexual arousal. When 31 male volunteers were subjected to the aromas of 30 different essential oils, each one exhibited a marked increase in arousal, based on measurements of brachial penile index and the measurement of both penile and brachial blood pressures. Among the scents that produced the most sexual excitement, was a combination of lavender and pumpkin fragrances. This study shows that fragrances enhance sexual desire by stimulating the amygdala, the emotional center of the brain.
In 1989, Dr. Joseph Ledoux , at New York Medical University, discovered that the amygdala plays a major role in storing and releasing emotional trauma. From the studies of Dr. Hirsch and Dr. Ledoux we can conclude that aromas may exert a profound effect in triggering a response from this almond-shaped neuro-structure. In studies conducted at Vienna and Berlin Universities, researchers found that sesquiterpenes, a natural compound found in essential oils of Vetiver, Patchouli, Cedarwood, Sandalwood and Frankincense, can increase levels of oxygen in the brain by up to 28 percent (Nasel, 1992).
Such an increase in brain oxygen may lead to a heightened level of activity in the hypothalamus and limbic systems of the brain, which can have dramatic effects on not only emotions but on learning, attitude, and many physical processes of the body such as: immune function, hormone balance, and energy levels. High levels of sesquiterpenes also occur in Melissa, Myrrh, Cedarwood, and Clove essential oils. Therapeudic grade Essential oils can provide many benefits to the human body without side effects, whether it is through diffusing or simply inhaling the aroma straight from the bottle. Proper stimulation of the olfactory nerves may offer a powerful and entirely new form of therapy that could be used as an adjunct against many forms of illness. Therapeutic essential oils, through inhalation, may occupy a key position in this relatively unexplored frontier in medicine. Resources
Hirsch, AR, Inhalation of Odorants for Weight Reduction, Int J Obes, 1994, page 306
Alan R. Hirsch, MD, FACP, Dr. Hirsch’s Guide to Scentsational Sex, Harper Collins, 1998 1993 Dec. 20;58(1-2):69-79
LeDoux, JE, Rationalizing Thoughtless Emotions, Insight, Sept. 1989