A SINGLE-PARAMETER, OXYGENATED HEMOGLOBIN, CAN BE USED TO QUANTIFY EXPERIMENTAL IRRITANT-INDUCED INFLAMMATION

To quantify the dose-response relation of irritant-induced erythema, w e examined inflammation in human skin after application of an irritant , using perpendicular polarized photography and diffuse reflectance sp ectroscopy as compared to clinical visual scoring, The ventral forearm s of 11 healthy subjects were patch-tested for 24 h under occlusion in hm chambers with five concentrations of the irritant sodium lauryl su lfate, The tested sites and three control sites were evaluated clinica lly for erythema at 24, 48, and 72 h after occlusion, photographed usi ng standard and perpendicular polarized photography, and measured by d iffuse reflectance spectroscopy, Ah photographs were evaluated for ery thema by three investigators, Diffuse reflectance spectra were analyze d, and changes in apparent oxyhemoglobin and deoxyhemoglobin concentra tions were estimated, Clinical and photographic assessments of erythem a yielded similar linear dose-response relations, A linear dose-respon se relation, with no minimum threshold, also was obtained for changes in the apparent oxyhemoglobin concentration with increasing irritant d ose, whereas the apparent deoxyhemoglobin concentrations were unchange d with increasing dose, These results show that diffuse reflectance sp ectroscopy permits the characterization of irritant-induced inflammati on in terms of a single parameter, the apparent concentration of oxyhe moglobin, and that irritant-induced inflammation primarily involves th e capillaries and the superficial arterial plexus.