THE NATURE OF TRIBROMOSALICYLANILIDE PHOTOALLERGY.

Three patients with photoallergy to 3,4',5 tribromosalicylanilide (TBS) following the use of a germicidal soap were studies to determine the mechanism of their photoallergy. None of these subjects had undergone previous patch or photopatch testing. Duplicate patches of purified TBS and its photoproducts 4', 5 dibromosalicylanilide (DBS). 4' monobromosalicylanilide (MBS), and salicylanilide were applied to the skin of the back. One set of patches was irradiated using a source of long ultravoilet whereas all ultraviolet radiation was regorously excluded from the second set. In one patient the results were consistent with a plain contact allergy to the photoproducts DBS and MBS. In a second patient irradiation of any of the three brominated salicylanilides resulted in a reaction whereas no reactions were observed in the dark. A free radical mechanism may be responsible for the formation of the complete antigen in this patient. In the third patient both mechanisms appeared to coexist. Reactions to commercial-grade TBS did not differ from those obtained with pure TBS. [ABSTRACT FROM AUTHOR]