Adulterant —A substance which was not originally present in the oil at the time of distillation added to an essential oil. An adulterant can be artificial or natural.
Base Oil (Carrier Oil) —Vegetable or nut oils such as Sweet Almond, Grapeseed, and Jojoba.
Diffuser —A device that disperses essential oils into an area. The three basic types are clay, candle and electric.
Dilute —Adding a small amount of essential oil to a larger amount of base oil to make it safe for use on the skin.
Distillation —Method used to extract essential oil from the plant. Steam distillation is the most common form of distillation.
GC/MS (Gas Chromatograph/Mass Spectrometer) —A device used by analytic chemists to determine the precise make-up of a given substance. Used in aromatherapy to determine the precise chemical constituents of an essential oil, and whether the oil is pure or adulterated with synthetic chemicals or other products.
Essential Oil —Highly aromatic substance found in specialized cells of certain plants. Technically, when this substance is in the plant, it is called an “essence.” After distillation of a single type of plant, the aromatic substance is referred to as an essential oil.
Herbally Infused Oil —These are oils that carry the medicinal properties of certain herbs. Carrier oil is infused with the medicinal herb, the plant is strained off, and the remaining oil can be used directly on the skin.
Neat —Use of an undiluted essential oil on the skin.
Notes —As in top, middle, and base notes. A type of classification system based on aroma, to identify certain oils. Generally, essential oils from citrus peels are top notes, essential oils from flowers, leaves and stems are middle notes, and essential oils from roots are base notes.
Orifice Reducer —A device used to reduce the size of the opening of a bottle, making dispensing the essential oil easier and more accurate.
Oxidation —When oxygen, light or heat interacts with essential oils, the essential oil begins to deteriorate over time. This can cause the essential oil to become skin irritating. It happens over the period of 1–3 years with oils high in monoterpenes, phenols and oxides, and more slowly with the other chemical families.
Phototoxic —The use of the oil makes one’s skin more prone to damage from the sun’s UV rays. Primarily the citrus oils, especially Lemon and Bergamot, as well as Angelica oil, are phototoxic oils.
Volatile —Describes how quickly a substance disperses itself into the air. In aromatherapy, top note essential oils may be referred to as “highly volatile,” meaning that they disperse quickly out of the bottle and into the air.