Wash test method: Hannuksela and Kinnunen1 developed a wash test method to determine the effect of moisturizers in preventing irritant contact dermatitis (ICD). Twelve healthy female students washed the outer aspects of their upper arms with a liquid dishwashing detergent for one minute twice daily for one week. Eight commercial moisturizers were applied to the left upper arm just after each washing while the other arm was left untreated. During the second week, the left upper arm only was treated with the moisturizers twice daily.
Transepidermal water loss (TEWL) was found to increase during the washing period by 13 g/m2/hr in the untreated arm, while the increase in the treated areas was only 3 g/m2/hr. Further, visible dermatitis appeared on the untreated arm while the treated areas remained objectively and subjectively free from symptoms and signs. Blood flow also increased significantly in the washed, untreated arm, but did not change in the arm treated with moisturizers.
During the second week, the dermatitis on the washed, untreated arm disappeared and the laser Doppler values normalized. The TEWL values also decreased to near normal. The mean decrease was more pronounced when moisturizers with a high fat content were used but due to inter-individual variations, the differences between the results for the eight moisturizers were not statistically significant. Comparing the effects of a moisturizer to no treatment after the one-week wash out period revealed that the use of moisturizers enhanced the healing process significantly.
Cross-over design: Halkier-Sørensen and Thestrup-Pedersen2 utilized a cross-over design to evaluate the efficacy of a moisturizera used by 111 cleaners and kitchen assistants during their everyday work. The population was divided into two groups—56 workers who used the test moisturizer only on their hands for the first two weeks and no emollient during the subsequent two weeks, and 55 workers using the same protocol but in reverse; i.e. no test moisturizer for the first two weeks and the same moisturizer as the first group during the subsequent two weeks. The moisturizer was found to prevent the development of skin dryness, as indicated by electrical capacitance (epidermal hydration), which decreased significantly when the subjects were not using the moisturizer.