Carrier oil, also known as base oil or vegetable oil, is used to dilute essential oils and absolutes before they are applied to the skin in massage and aromatherapy. They are so named because they carry the essential oil onto the skin. Carrier oils do not contain a concentrated aroma, unlike essential oils, though some, such as olive, have a mild distinctive smell. Neither do they evaporate like essential oils, which are more volatile. The carrier oils used should be as natural and unadulterated as possible. Many people feel organic oils are of higher quality. Cold-pressing and maceration are the two main methods of producing carrier oils.
There is a range of different carrier oils, each with a various therapeutic properties. Choosing an oil will depend on the area being massaged, the presenting conditions and the clients sensitivity and requirements. For massage, viscosity is a major consideration; for example, grapeseed oil is typically very thin, while olive oil is much thicker. Sunflower, sweet almond and grapeseed oils have viscosities midway between these extremes. Carrier oils can be easily blended to combine their properties of viscosity, acceptability, lubrication, absorption, aroma and so forth.