Studies with brain wave frequency has shown that smelling lavender increases alpha waves in the back of the head, which are associated with relaxation. Fragrance of Jasmine increases beta waves in the front of the head, which are associated with a more alert state.

Scientific studies have also shown that essential oils contain chemical components that can exert specific effects on the mind and body. Their chemistry is complex, but generally includes alcohols, esters, ketones, aldehydes, and terpenes. The effect of these chemical components are summarized in the accompanying table.

Name of the chemical component Properties of the chemical component Essential oils that contain the chemical
Aldehydes anti-inflammatory,calming, sedative and anti-viral. Characteristic lemon-like smell, such as lemon grass, lemon balm, citronella, eucalyptus
Alcohols bactericidal (kills bacteria), stimulant, energizing, vitalizing, antiviral, diuretic. Our pancreas produce 32 kinds of alcohol for use in human metabolism. Rose, petitgrain, rosewood, peppermint, myrtle, tea tree, sandalwood, patchouli, and ginger
Phenols strongly bactericidal, tonic, stimulates immune system, invigorating, warming. Can produce slight liver toxicity if taken high doses for extended periods of time. Used in lip balms and cough drops. Clove, cinnamon, thyme, oregano, savory, cumin.
Cetone (Ketones) wound healing, mucolytic (eases the secretion of mucous), stimulates new cell growth. used as a nail polish. Camphor, rosemary, sage, eucalyptus globulus and hyssop
Terpenes Very stimulating, potential skin irritants, anti-viral properties. Lemon, orange, bergamot, black pepper, pine oils, nut meg and angelica.
Sesquiterpenes anti-phlogistic (moves fluids), anti-inflammatory, sedative, anti-viral, anti-carcinogenic, bacteriostatic and immune stimulant Blue chamomiles, immortelle, tansy, yarrow and tagetes.
Esters anti-fungal, sedative, calming, spasmolytic, fungicidal, anti-inflammatory. Roman chamomile, lavender, clary sage, petitgrain, bergamot.
Lactones (part of ester group) anti-inflammatory, mucolitic arnica, elecampane
Ethers harmonizing to the nervous system. antiseptic, stimulant, expectorant (increases secretions), spasmolytic, and diuretic. Cinnamon, clove, anise, basil, tarragon, parsley, and sassafras.

Each essential oil contains as much as 100 chemical components, which together exert a strong effect on the whole person. Depending on which component is predominating in an oil, the oils act differently. For example, some oils are relaxing, some soothes you down, some relieves your pain, etc. Then there are oils such as lemon and lavender, which adapt to what your body needs, and adapt to that situation. (These are called "adaptogenic"). The mechanism in which these essential oils act on us is not very well understood. What is understood is that they affect our mind and emotions. They leave no harmful residues. They enter into the body either by absorption or inhalation.

A fragrance company in Japan conducted studies to determine the effects of smell on people. They have pumped different fragrances in an area where a number of keyboard entry operators were stationed and monitored the number of mistakes made as a function of the smell in the air. The results were as follows:

When exposed to lavender oil fragrance (a relaxant), the keyboard typing errors dropped 20 percent.
When exposed to jasmine (an uplifting fragrance), the errors dropped 33 percent
When exposed to lemon fragrance (a sharp, refreshing stimulant), the mistakes fell by a whopping 54 percent!