Laser-Doppler flowmetry in the investigation of irritant compounds on human skin

The value of laser-Doppler flowmetry was assessed in the evaluation of increased microvascular blood flow caused by the application of low concentrations of irritant compounds on the skin. Laser-Doppler flow values were compared with a visual scoring system for erythema and with skin vapour loss measurements. To this end patch tests were performed on the volar side of the forearm of 24 healthy Caucasian volunteers. The test substances were sodium lauryl sulphate 0.5 g/v%, 1 g/v%, 2 g/v% and phenol 5.0 g/v% in aqua dest. Distilled water served as a control. Laser-Doppler flow and skin vapour loss measurements were performed before and after an application time of 24 h. Data obtained with skin vapour loss measurements and with the visual scoring system demonstrated a statistically significant contribution of substance- as well as subject-related factors to the obtained scoring patterns. The results of laser-Doppler flow measurements were less consistent and could only partly be explained in this way, indicating that other factors also influence the microvascular blood flow in the skin. In this investigation laser-Doppler flowmetry and the visual scoring system were equally sensitive. The results of all three methods make it clear that (analogous to experience in daily life) barrier function impairment and inflammatory response caused by irritant compounds vary in different subjects. For the elucidation of the pathogenesis of irritant contact dermatitis further (longitudinal) investigations on the possible predictive value of skin blood flow measurements will be necessary.