By the Middle ages essentail oils were common use throughout Europe. These days Aromatherapy is based mainly on the work of some French Doctors. The Essential oils are extracted from flowers, plants, roots and trees. Essential oils should should only be taken from organically grown plants. The most common form used for extraction is distillation.
Distillation heats the plant until the oil vaporizes.
Another method is Maceration. This is crushing the rind of citrus fruit to obtain the oil. Plant oils may be broken down into chemicals such as phenols, ketones and alcohols which may have therapeutic properties. The scents released by the essential oils acts on the hypothalamus which is a part of the brain that influences the hormonal system. In theory, essential oils are thought to be absorbed into the body either through the pores of the skin during massage or inhalation.