Comparison of patch test positivity after 24 and 48 hours of occlusion time in patients of allergic contact dermatitis: A prospective study.

Though there is no significant difference in patch test positivity among ISS allergens after either occlusion time, 48 h occlusion performs significantly better compared with 24 h, when reactions of all allergens (ISS, patient material and parthenium acetone extract) are analysed together.