Cleaning work is a common cause of both irritant and allergic contact dermatitis. Cleaning agents for industrial and household use are registered in the Danish Product Register Data Base (PROBAS) according to a special notification rule issued by the Danish Environmental Protection Agency. About 2350 registered washing and cleaning agents containing about 1250 different chemical substances were marketed in Denmark in February 1992. The occurrence of 49 contact allergens in 16 different product types within washing and cleaning agents were listed. Preservatives and surface active agents made up the main part of contact allergens. Isothiazolinones and formaldehyde releasers were the most commonly registered preservatives, and coconut diethanolamide the most commonly registered surface active agent. The major product types registered as containing contact allergens were general cleaners, skin cleaners, hair shampoos, and floor polishes.