Aromatherapy is a derivative of herbal medicine, which is itself a subset of the biological or nature-based complementary and alternative medicine (CAM) therapies.

Aromatherapy has been defined as the therapeutic use of essential oils from plants for the improvement of physical, emotional, and spiritual well-being. The proponents of aromatherapy claim it is an all-natural, nontoxic adjunct to conventional medicines.

Essential oils are volatile liquid substances extracted from aromatic plant material by steam distillation or mechanical expression. The major chemical components of essential oils include terpenes, esters, aldehydes, ketones, alcohols, phenols, and oxides, which are volatile and may produce characteristic odors. Different types of oils contain varying amounts of each of these compounds, which are said to give each oil its particular fragrance and therapeutic characteristics.

Synthetic odors are often made up of many of the same compounds, which are synthesized and combined with other novel odor-producing chemicals.

Aromatherapy is used or claimed to be useful for a vast array of symptoms and conditions. Published studies regarding the uses of aromatherapy have generally focused on its psychological effects (used as a stress reliever or anxiolytic agent) or its use as a topical treatment for skin-related conditions.

Practitioners of aromatherapy apply essential oils using several different methods, including direct inhalation via diffuser or drops of oil placed near the patient (e.g., on a pillow); aromatherapy massage, which is the application to the body of essential oils diluted in a carrier oil; and other direct and indirect applications such as placing drops of oil in bathwater, lotions, or dressings.

National Cancer Institute. Aromatherapy and Essential Oils (PDQ). Internet. Accessed on January 25, 2016.