The validity and practicality of sun-reactive skin types I through VI.

lTlhe concept of sun-reactive "skin typing" was r created in 1975'for a specific need: to be able to classify persons aitlt ultife skininu4s11q ss1sc111s correct initial doses of ultraviolet A (UVA) (in joules per cubic centimeter) in the application of the then newly developed technique for the treatment of psoriasis-oral methoxsalen photochemotherapy (PWA).' The need arose as a result of exoerience with several patients who were a "dark" phtnotype (brown or even black hair, and some with brown eyes) but, to our surprise, deveioped severe phototoxic reactions following oral ingestion of 0.6 mglkg of methoxsalen and then, two hours later, were exposed to 4 to 6 J/cm'. These initial doses were obviously too high, and it was then understood that the estimation of the white-skinned person's tolerance level to oral PUVA could not be based solelv on the phenotype (hair and eye color). A simple approach was necessary for the impending largescale oral PUVA photochemotherapy trials in the United States in the mid-1970s.1. It was decided that a brief personal interview regarding the history of the person's unburn and suntan experience was one approach to estirnate the skin tolerance to uitraviolet radiation (UVR) exposure. Editorial