A STUDY OF SKIN-RESPONSES TO FOLLOW-UP, RECHALLENGE AND COMBINED EFFECTS OF IRRITANTS USING NONINVASIVE MEASUREMENTS

Irritant contact dermatitis is a common clinical problem. Primary irri tation can be easily recognized, but cumulative irritation by daily ex posure is hard to be diagnosed and the condition may fail to be clear even away from work. The mechanism of irritant dermatitis produced by repeated or combined exposure to clinical or subclinical doses of irri tants is still poorly understood, In order to find out whether the sub clinical doses of irritants affect each other by repeated or combined exposure according to their concentrations, non-invasive measurements, transepidermal water loss and laser Doppler flowmetry were used. Sodi um lauryl sulfate, sodium hydroxide and benzalkonium chloride were ser ially diluted and patch-tested with large Finn chambers on Scanpor tap e on the back of normal human volunteers and responses were followed u p for 7 days. Twice repeated exposure with subclinical doses of irrita nts at 1 day intervals were also performed, Repeated daily application s for 5 days with subclinical doses of single or premixed irritants we re performed to know the combined irritating effect. The irritant resp onse was well correlated to the concentration of the irritants. Howeve r, increased response was not observed when subclinical doses were rec hallenged on the previously patch tested sites. Twice-repeated exposur e of subclinical doses of irritants increased skin irritancy when meas ured by transepidermal water loss and laser Doppler flowmetry. Some co rrelation and some discrepancies were observed between different evalu ation methods in combined and repeated application tests with irritant s of subclinical doses. Responses of skin irritancy induced by subclin ical doses showed somewhat different pattern from that given strong ir ritants. So, when evaluating the patients suspicious of irritant derma titis, patch testing with the possible combination of the irritants or repeated test may be helpful to verify their effect on the skin even at a weak concentration.