Aromatherapy is the treatment or prevention of disease by use of essential oils. Two basic mechanisms are offered to explain the purported effects. One is the influence of aroma on the brain, especially the limbic system through the olfactory system. The other is the direct pharmacological effects of the essential oils.
An essential oil is a concentrated, hydrophobic liquid containing volatile aroma compounds from plants. Essential oils are also known as volatile, ethereal oils or aetherolea, or simply as the "oil of" the plant from which they were extracted, such as oil of clove. An oil is "essential" in the sense that it carries a distinctive scent, or essence, of the plant. Essential oils do not as a group need to have any specific chemical properties in common, beyond conveying characteristic fragrances.
The essential oils are volatilized or diluted in a carrier oil and used in massage, diffused in the air by a nebulizer or by heating over a candle flame, or burned as incense, for example.
Just as different foods contain elements that nourish your body in different ways, each essential oil carries unique properties which can improve or enhance your physical and mental well being. Scent is the most enduring of our senses. It has the power to transform our emotions, and heal our bodies. It can take us to another place and time.
Some of the Aromatherapy oils and materials include:
Infusions : Aqueous extracts of various plant material (e.g. infusion of chamomile).
Carrier oils : Typically oily plant base triacylglycerides that dilute essential oils for use on the skin (e.g. sweet almond oil).
Vaporizer (Volatized) Raw Herbs : Typically higher oil content plant based materials dried, crushed, and heated to extract and inhale the aromatic oil vapors in a direct inhalation modality.
Essential oils : Fragrant oils extracted from plants chiefly through steam distillation (e.g. eucalyptus oil) or expression (grapefruit oil). However, the term is also occasionally used to describe fragrant oils extracted from plant material by any solvent extraction.
Absolutes : Fragrant oils extracted primarily from flowers or delicate plant tissues through solvent or supercritical fluid extraction (e.g. rose absolute). The term is also used to describe oils extracted from fragrant butters, concretes, and enfleurage pommades using ethanol.
Herbal distillates or hydrosols : The aqueous by-products of the distillation process (e.g. rosewater). There are many herbs that make herbal distillates and they have culinary uses, medicinal uses and skin care uses. Common herbal distillates are rose, lemon balm and chamomile.
Phytoncides: Various volatile organic compounds from plants that kill microbes. Many terpene-based fragrant oils and sulfuric compounds from plants in the genus "Allium" are phytoncides, though the latter are likely less commonly used in aromatherapy due to their disagreeable odors.
NOTE: Because essential oils are highly concentrated they can irritate the skin when used neat, that is undiluted. Therefore, they are normally diluted with a carrier oil for topical application. Phototoxic reactions may occur with citrus peel oils such as lemon or lime. Also, many essential oils have chemical components that are sensitizers (meaning that they will after a number of uses cause reactions on the skin, and more so in the rest of the body). Some of the chemical allergies could even be caused by pesticides, if the original plants are cultivated. Some aromatherapy oils can be toxic to some domestic animals, with cats being particularly prone.