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

Abstract

BACKGROUND: 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. OBJECTIVES: 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. METHODS: 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). RESULTS: Significantly stronger cumulative irritation was observed in stingers than in non-stingers for both irritants (visual scoring, stratum corneum hydration, and skin colour reflectance). CONCLUSIONS: 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.