Scents have been used to enhance mood, relieve stress, and cure diseases for centuries. Aromatherapy, a version of this ancient practice, was "invented" in the 1930s but became truly popular in the early 1990s. National chains of beauty salons and spas began to provide relaxation services, such as massage, that included aromatic oils and incense.

The inhalation of the scent of various aromatic plants or the application to the skin as essential oils was thought to affect a person's mood. Although no regulations for aromatherapy products were in effect at the end of the twentieth century, many brands of aromatic oils and incense were sold for personal use across the nation. Among the brands are pure aromatic products, some made from chemical derivatives, and others produced by digital technology and supplied via the Internet (see entry under 1990s—The Way We Lived in volume 5).

While aromatherapy is mostly...