A new type of erythemal radiometer for use in phototherapy

A new type of radiometer is described which, when exposed to ultraviolet radiation lamps, displays the time required to achieve a minimal erythema. The radiometer incorporates a switch on the front panel to allow for the erythemal sensitivity of different sun-reactive skin types. The instrument was exposed to a number of different lamp/filter combinations commonly used for phototherapy, and in each case indicated an exposure time to within +/- 10% of that determined by combining the spectral irradiance with the erythema action spectrum. Good agreement was also obtained between the exposure times necessary to achieve 24 h minimal erythema in Caucasian subjects of different sun-reactive skin types, and those exposure times predicted by the erythemal radiometer.