Aromatherapy uses plant materials and aromatic plant oils including essential oils, and other aromatic compounds which claim to improve psychological or physical well-being. It is employed as a complementary therapy or as a form of alternative medicine alongside standard treatment. Some popular essential oils are lemon, lavender, bergamot, and peppermint oil(s).

Historically, Dioscorides described the use of oils in the First Century. Later, Avicenna isolated essential oils by steam distillaion,  

and used them as medicines in the Eleventh Century. The use of essential oils for therapeutic, spiritual, hygienic and ritualistic purposes

goes back to many ancient civilizations (Chinese, Indian, Egyptian, Greek, and Roman), who used them as cosmetics, perfumes and drugs.

Aromatherapists use essential oils as topical application, massage, or inhalation. However, all claims about the efficacy of essential oils are not clinically well-substantiated. The term holistic medicine also has lately gained popularity which implies treatment of the whole person (body, mind, emotions, and spirit). Systems such as naturopathy, ayurveda, acupuncture, reflexology, and homeopathy are included in alternative medicine.

Materials employed in aromatherapy include: (i) fragrant oils from flowers and plants obtained by using solvents, (ii) Aroma lamps or diffusers, (iii) Carrier oils, (iv) Essential oils like eucalyptus oil, (v) Herbal distillates or hydrosols, e.g.,rose water, chamomile, and lemon balm, (v) Aqueous extracts and infusions, and (vi) Vaporizers for inhaling aromatic oil vapors. 

Mode of action: Firstly, the influence of aroma on the brain is through the limbic system, and secondly the direct action of the essential oil on the body cells. It works by stimulating the smell receptors in the nose, which send messages through nerves to the limbic system, the part of the brain which controls emotions.

Benefits of Aromatherapy: Research on the therapeutic effectiveness  of aromatherapy is limited. However, it is suggested that benefits include; (i) Relief from anxiety and depression, (ii) Improved quality of life in people with chronic diseases, (iii) Improved sleep, (iv)

Relief of pain in osteoarthritis, and pain of kidney stones. Thus, aromatherapy may be used for stress relief, as an antidepressant for managing psychiatric disorders, to increase energy levels, to reduce headaches, to regulate sleep, to strengthen the immune system, and to improve digestion. These claims do need further scientific scrutiny. Side effects of topical application and ingested essential oil(s) are yet to be worked out in detail.