The main branches of aromatherapy include:
- Home aromatherapy (self treatment, perfume & cosmetic use)
- Clinical aromatherapy (as part of pharmacology and pharmacotherapy)
- Aromachology (the psychology of odors and their effects on the mind)
Some of the materials employed include:
- Essential oils: Fragrant oils extracted from plants chiefly through 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.
- Phytoncides: Various volatile organic compounds from plants that kill microbes. Many terpene based fragrant oils and sulfuric compounds from plants in genus "Allium" are Phytoncides, though the latter are likely less commonly used in aromatherapy due to their disagreeable smells.
- Hydrosols: The aqueous by-products of the distillation process (e.g. rosewater). Hydrosol used are limited to plants such as rose and camomile since most hydrosols have unpleasant smells.
- Infusions: Aqueous extracts of various plant material (e.g. infusion of chamomile)
- Carrier oils: Typically oily plant base triacylglycerides that are used to dilute essential oils for use on the skin (e.g. sweet almond oil)
When aromatherapy is used for the treatment or prevention of disease, a precise knowledge of the bioactivity and synergy of the essential oils used, knowledge of the dosage and duration of application, as well as, naturally, a medical diagnosis, are required. In the Anglo-Saxon world, even among "natural" practitioners like herbalists or naturopaths, aromatherapy is regarded more as an art form than a valid healing science. At best, it is viewed as a complementary and seldom the only treatment prescribed. On the continent, especially in France, where it originated, aromatherapy is incorporated into mainstream medicine. There, the use of the anti-septic properties of oils in the control of infections is emphasized over the more "touchy feely" approaches familiar to English speakers. In France some essential oils are regulated as prescription drugs, and thus administered by a physician. In many countries they are included in the national pharmacopeia, but up to the present moment aromatherapy as science has never been recognized as a valid branch of medicine in the United States, Russia, Germany, or Japan.
Essential oils, phytoncides and other natural VOCs work in different ways. At the scent level they activate the limbic system and emotional centers of the brain. When applied to the skin (commonly in form of "massage oils" i.e. 1-10% solutions of EO in carrier oil) they activate thermal receptors, and kill microbes and fungi. Internal application of essential oil preparations (mainly in pharmacological drugs; generally not recommended for home use apart from dilution - 1-5% in fats or mineral oils, or hydrosoles) may stimulate the immune system,
Skeptics argue that while pleasant scents can be relaxing, lowering stress and related effects, there is currently insufficient scientific proof of the effectiveness of aromatherapy. Like many alternative therapies, few controlled, double-blind studies have been carried out—a common explanation is that there is little incentive to do so if the results of the studies are not patentable. There are some treatments generally accepted in Western medicine to give a form of relief for the airways in case of cold or flu, such as mint and eucalyptus essential oils. Skeptical literature often depicts aromatherapy as based on anecdotal evidence of its benefits rather than proof that aromatherapy can cure diseases. Some skeptics acknowledge that aromatherapy has limited scientific support but argue that its claims go beyond the data or that the studies are not adequately controlled and peer reviewed. If there can be positive effects, there can also be negative ones if used incorrectly or in bad combinations especially with traditional pharmacology.
The term "aromatherapy" has been applied to such a wide range of products that almost anything which contains essential oils is likely to be called an "aromatherapy product", rendering the term somewhat meaningless in that context.
Some proponents of aromatherapy believe that the claimed effect of each type of oil is not caused by the chemicals in the oil interacting with the senses, but that the oil contains a distillation of the "life force" of the plant from which it is derived that will "balance the energies" of the body and promote healing or well-being by purging negative vibrations from the body's energy field. Arguing that there is little scientific evidence that healing can be achieved, or that the claimed "energies" even exist, many skeptics reject this form of aromatherapy as pseudoscience or even quackery.
