Fragrant oils have been used for thousands of years to lubricate the skin, purify air, and repel insects. Ancient Egyptians used fragrant oils for bathing and massage. Essential oils of plants have been used medicinally through application directly to the skin (usually diluted), as a part of massage, added to bathwater, via steam inhalation, or in mouthwashes. Aromatherapy is a technique in which essential oils from plants are used with the intention of preventing or treating illness, reducing stress, or enhancing well-being. Fragrance oils and products containing man-made compounds are not used in the practice of genuine aromatherapy. Although many gift shops sell scented candles, pomanders, and potpourri as "aromatherapy," genuine aromatherapy treatments use higher strength (concentrated) essential oils drawn from various herbs. There is no formal training or licensing procedure for aromatherapists in the United States. This technique is offered by a wide range of practitioners with licenses in other fields, including massage therapists, chiropractors, and other therapists.