The lactic acid stinging test predicts susceptibility to cumulative irritation caused by two lipophilic irritants.

Skin exposure to lipophilic irritants at workplaces is a risk factor for the development of occupational irritant hand dermatitis. Suitable lipophilic model irritants to be used in repeated irritation studies in volunteers are needed to gain a better understanding of the chemical-dependent mechanisms of skin irritation. To investigate acute and cumulative irritation elicited by two new lipophilic model irritants, octane (CAS No. 111-65-9) and cumene (CAS No. 98-82-8), in stingers as compared with non-stingers. Short-time occlusive and repetitive occlusive irritation patch tests were performed over 5 days with octane and cumene in two groups of healthy volunteers (n = 15 each) who were classified as stingers and non-stingers according to a preceding lactic acid stinging test. Acute and cumulative irritation was quantified using clinical assessments and bioengineering methods (laser Doppler flowmetry, transepidermal water loss, capacitance measurements, and skin colour reflectance). Significantly stronger cumulative irritation was observed in stingers than in non-stingers for both irritants (visual scoring, stratum corneum hydration, and skin colour reflectance). The preliminary results suggest the existence of a distinct sub-population with increased susceptibility to cumulative irritation induced by lipophilic irritants that can be identified by the lactic acid stinging test.