A preliminary study on photoaddition and erythema due to UVB radiation.

The spectral irradiance of narrow band and broad spectrum radiation sources have been measured and the erythemally effective irradiance calculated by weighting the spectral irradiance of each source by an erythema action spectrum for human skin and integrating over the range of wavelengths in each spectrum. The ratio of the erythemally effective irradiances determined in this manner have been compared with the ratio of exposure times necessary to produce a delayed minimal perceptible erythema on the trunk skin of fair-skinned subjects irradiated with the two different sources. There was close agreement between the two ratios, supporting the notion of photoaddition applied to erythema elicited by UVB radiation.