Response to thermal stimuli in skin pretreated with sodium lauryl sulfate

Skin irritation is mostly a multifactorial process. Competitive effects of different chemical irritants are well known. This study investigates the influence of a thermal stimulus on skin pre-irritated with sodium lauryl sulfate (SLS). Seventy-seven volunteers were patch-tested with SLS 0.25% and 0.5% for 48 h. Water served as control. Skin reaction was evaluated by measurement of transepidermal water loss, skin blood flow and skin color. After measurement, a thermal stimulus was applied on the test area. The increase in skin blood flow was measured. There was a significant correlation between the degree of irritation and the increase in skin blood flow after thermal stimulus. Pre-irritated skin reacted to thermal stimulus with a shorter and sharper increase in skin blood flow. This increase was dependent on the SLS concentration. Hence, the thermally stimulated blood flow may be a model of non-chemical irritation and seems to be a relevant co-factor in the pathogenesis of irritant dermatitis.