Carrier oils, also referred to as base or vegetable oils, are used to dilute essential oils before being applied to the skin. They encapsulate the essential oil, making absorption easier. Different aromatherapy carrier oils offer different properties and the choice can depend on the therapeutic benefit being sought.
Carrier oils are generally cold-pressed vegetable matter derived from the fatty portions of the plant. Unlike essential oils that evaporate and have a concentrated aroma, aromatherapy carrier oils do not evaporate or impart their aroma as strongly as essential oils.
Most oils bought in the grocery store are not cold-pressed. Instead, they are heated and therefore have less therapeutic benefit than cold-pressed carrier oils. Mineral oil should not be used in massage therapy because it is not a natural product. It is also said that it can prevent essential oil absorption into the skin.