Fenticlor is an aryl sulfide having two 5-chloro-2-hydroxyphenyl groups attached to sulfur. Fenticlor is an antibacterial and antifungal agent for topical use. Since it may cause photosensitivity, it is nowadays mostly used in veterinary medicine. Fenticlor has been used in the treatment of eye and ear infections. The activity of the compound in treating otitis externa has been evaluated by Stride (1962) and in the treatment of various skin mycoses by Jung (1954) and Richter (1950). Due to the extremely low oral toxicity the compound has been used internally in the treatment of deep seated skin infections which are not accessible to external treatment. Fentichlor is bacteriostatic or bactericidal, according to concentration, to Staph. aureus and E. coli. The antifungal and antibacterial properties of fentichlor were discovered in the 1950s and 1960s. The mechanism of action of these properties was later found to involve the inhibition of active transport through an energy-uncoupling mechanism. As a result of these findings, the pharmaceutical importance of including fentichlor in various products rose appreciably in the 1960s. The products containing fentichlor that were manufactured and distributed worldwide included antibacterial and antifungal creams and ointments, hair creams, cosmetics, and hand soaps; however, these products were never extensively used in the United States. The past use of fentichlor as a biocide in water treatment facilities was more common in the United States. The last known products that contained fentichlor in the United States were 2 biocides that were used in water treatment facilities and that were both discontinued in 1993.