New and emerging cosmetic allergens.

Human skin is exposed to a large variety of cosmetic allergens. Most allergic contact dermatitis occurs after exposure to fragrance, preservatives, and hair dyes. Such reactions can often be occult. As a result, a high index of suspicion is needed in assessing the patient with facial or cosmetic dermatitis. This contribution looks at why such a large number of chemicals are in everyday usage, at how dermatologists monitor trends in allergy to cosmetics, and at a number of new and emerging allergens to consider in the assessment of suspected cosmetic allergy.