Abstract: Forty-five guinea pigs were used to investigate the mutual iufluence between primary irritant contact dermatitis (PICD) and allergic contact dermatitis (ACD) during their development.The result showed that guinea pigs with ACD had an increased response to potassium dichromate,which was characterized by the reduce of irritant threshold and increase of response intensity in skin.Also in the presence of PICD the minimum challenge concentration needed for the appearance of ACD might be reduced.This means that ACD can be caused by lower challenge concentrtion of sensitizer in the presence of PICD.