An essential oil is a concentrated, hydrophobic liquid containing volatile aroma compounds fromplants. 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. Essential oils are generally extracted by distillation. Other processes include expression, or solvent extraction. They are used in perfumes, cosmetics, soap and other products, for flavoring food and drink, and for scenting incense and household cleaning products. Various essential oils have been used medicinally at different periods in history. Medical applicationproposed by those who sell medicinal oils range from skin treatments to remedies for cancer, and are often based on historical use of these oils for these purposes. Such claims are now subject to regulation in most countries, and have grown more vague to stay within these regulations.
Interest in essential oils has revived in recent decades with the popularity of aromatherapy, a branch of alternative medicine which claims that the specific aromas carried by essential oils have curative effects. 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.
Aromatherapy is a form of alternative medicine that uses volatile plant materials, known as essential oils, and other aromatic compounds for the purpose of improving a person's mood, cognitive function or health. The effectiveness of aromatherapy is yet to be scientifically proven, however some evidence exists that essential oils may have therapeutic potential. Since some essential oils such as tea tree, have demonstrated anti-microbial effects, it has been suggested that they may be useful for the treatment of infectious diseases. The evidence base for the efficacy of aromatherapy used to treat medical conditions remains poor with a particular paucity of methodologically rigorous studies.