Cosmetics are defined as "articles with mild action on the human body, which are intended to be applied to the human body through rubbing, sprinkling or other methods, aiming to clean, beautify and increase the attractiveness, alter the appearance or to keep the skin or hair in good condition (The Pharmaceutical Affairs Law: Article 2)." Consequently, they include personal hygiene products such as shampoos, soaps and toothpaste. In Europe, 1% of the population is estimated to be allergic to fragrances and 2-3% to ingredients of cosmetics; 10% of outpatients patch-tested for cosmetics allergy were found to be positive. Allergenic ingredients of cosmetics can be fragrances, hair dye, preservatives, antioxidants, emollients, surfactants, UV absorbers, pigments or resins used in nail cosmetics. Among standard allergen series, eight substances are related to cosmetics; in Japan in 2003, p-phenylenediamine (hair dyes) induced allergic reactions with the highest rate of 7.9% in outpatients patch-tested (n=805), followed by fragrance mix No. 1 (4.0%, mixture of eight fragrances frequently used), colophony (3.2%, main contents of pine resin), lanolin alcohol (2.7%,emollients), and formaldehyde, parabens, Kathon CG (2.7% ,1.9% and 1.0%, respectively; preservatives). Cosmetic allergy symptoms tend to be mild except those caused by hair dye. However, the population exposed to cosmetics is huge and the number of ingredients used in cosmetics increased up to more than 6000. Here, major cosmetic ingredient allergens, mainly reported in Japan, are reviewed and discussed.