Influence of climatic conditions on the irritant patch test with sodium lauryl sulphate

Irritant patch testing with detergents is increasingly being used as a measure of skin barrier function, but there is evidence that climatic changes can influence the test outcome. In this study we investigated the relation between cutaneous reactivity to a detergent and climatic conditions. Between January 2000 and December 2001 epicutaneous patch testing with 0.5% sodium lauryl sulphate was performed on the forearm of 487 volunteers and evaluated by measuring transepidermal water loss (TEWL). Atopic individuals were excluded. Climatic conditions recorded by the German Meteorological Service were then compared with the test outcome. Climatic measurements 7 days before evaluation of the patch test were used to calculate an arbitrary mean value for each climatic parameter. A strong correlation was observed between temperature, steam pressure, absolute and relative humidity and the increase in TEWL, and most pronounced during winter and spring. The data provide experimental confirmation of epidemiological studies in which the incidence of irritant skin changes was found to be increased during the winter season with cold and dry air. For the first time, two formulae for adjusting TEWL values according to climatic conditions are presented. It is possible with these formulae to compare between a measured TEWL value and a calculated value.