Many substituted salicylanilides, particularly halogenated salicylanilides have strong anti-bacterial properties and in the past have been employed as bactericides in soaps. However, this has led to photoallergy causing serious adverse skin reactions. Although most photoallergens will elicit a response in only a small fraction of the people exposed 3,3',4',5-tetrachlorosalicylanilide (T₄CS-H) is unusual in inducing photoallergy in a high fraction of those exposed and displays a high specificity towards serum albumin. The proposed mechanism of the protein-photoallergen binding is thought to proceed via the formation of highly reactive species such as free radicals. The albumin in the skin is believed to be the carrier protein in the skin that binds with T₄CS⁻ to form an antigen.