DERMATOLOGISTS and physical therapists have, for many years, utilized infrared rays to counteract accidental overexposure to ultraviolet light. However, the chemical and physiological bases for this phenomenon have not been demonstrated and the fundamental nature of ultraviolet erythema has not been clarified. We became interested in studying the nature of infrared modification of ultraviolet erythema in hope that an investigation might contribute to our understanding of the physiology of the sunburn reaction. Review The 1929 study of Shattock and Waller is the only investigation we have found which concerned itself with the effect of infrared radiation on the cutaneous erythema produced by ultraviolet light.1 In their study it was shown that the application of heat during or after, but not prior to, ultraviolet radiation diminished and delayed the appearance of the erythema reaction. More recent studies of the infrared effect on induced ultraviolet damage have either been conducted