IMMEDIATE IRRITANT REACTIONS TO BENZOIC-ACID ARE ENHANCED IN WASHED SKIN AREAS

Factors affecting immediate irritant skin reactions are poorly underst ood. Our purpose was to study the effect of washing on reactions to be nzoic acid, a well-known immediate-type irritant. 12 test subjects was hed their left upper arms with a diluted dishwashing liquid 2x daily f or 6 days. Benzoic acid in a dilution series was tested on both upper arms on days 0, 3 and 6. The reactions were graded visually, and the b lood flow, skin color, transepidermal water loss and electrical capaci tance of the test sites were measured. On days 3 and 6, the benzoic ac id reactions were stronger on the washed arm than on the control arm. This was clinically visible and was associated with changes in blood f low and skin color measurements. Washing itself did not ususally cause visible erythema, but transepidermal water loss increased and electri cal capacitance decreased. Low concentrations of irritant substances, such as benzoic acid, may cause clinically relevant reactions in repea tedly washed skin. This should be taken into consideration in assessin g product safety in the cosmetic, medical and household chemical indus tries, and when tests for chemical skin irritancy are designed and the results of such tests interpreted.