A hand immersion test under laboratory-controlled usage conditions: the need for sensitive and controlled assessment methods

Exaggerated test conditions were frequently used to investigate the cutaneo us tolerance of detergent products in the past. As the sensitivity of newly designed biometric methods is steadily improving, the trend towards more r ealistic test conditions should be encouraged. A hand immersion test under laboratory-controlled usage conditions is presently described, fulfilling s uch principles. Panelists soaked their hands in 2 different hand dishwashin g liquids, 2x daily for 10 min each (with successive in-solution/out-of-sol ution cycles) for 4 consecutive days. Products were at usual dilution for d ishwashing liquids and were randomized between the dominant and non-dominan t hands of panelists. Visual scoring of erythema and dryness developing on the whole hands (scoring scales including interdigital areas and joints) du ring the week did not allow discrimination between the 2 products. However the dominant hands were significantly more susceptible to alterations than the non-dominant hands, regardless of product attribution. In contrast, ski n electrical measurements (Corneometer(R) CM800 and Skicon(R) 200) on the d orsum of the hands (muscle mass between thumb and index) and squamometry an alysis of tape stripping (harvested from the same site) yielded significant differences between the 2 products. In conclusion, a hand immersion test u nder realistic conditions has been described, which discriminates between p roducts when sensitive assessment methods are used to explore skin sites pa rtially protected from daily-life skin aggressions.