Acute irritation thresholds in subjects with type I--type VI skin

It has long been recognized that human skin can be subdivided into simple categories based on their sensitivity to sunlight--from Type I, never tans, always burns, to Type VI, marked constitutive pigmentation. There is also evidence that the more readily sunburnt type of skin is also more susceptible to the effect of irritants. In the present work, the irritancy threshold for sodium lauryl sulfate (SLS) has been assessed using a recently described 4-h acute skin irritation patch test. A total of 110 subjects covering all 6 skin types were examined and their threshold for acute irritancy defined as the lowest concentration of SLS, applied under 4-h occlusion, which would induce a clinically detectable irritant response. The SLS dose response generated using a range of concentrations (0.1%-20%) demonstrated that there was no significant difference between the groups under these test conditions. Even for Type VI skin (n = 25), the dose-response curve fell within the general pattern. These results reinforce the general applicability of predictions of acute irritant potential made in groups of human volunteers.