The present invention provides a pharmaceutical composition by a novel action mechanism without serious side effects for delayed hypersensitivity and a screening method of the same. The invention also provides a novel assay method of inhibitors/suppressive agents of PAR-2. The invention relates to a pharmaceutical composition for delayed hypersensitivity containing one or two or more active ingredients selected from the group consisting of inhibitors of PAR-2 and suppressive agents of PAR-2 gene expression and a pharmaceutically acceptable carrier, and to a method for screening active ingredients for pharmaceutical composition for delayed hypersensitivity by contacting a subject substance with cells expressing PAR-2 and by determining expression or activity of PAR-2. The invention also relates to a method for detecting or quantifying actions of the subject substance for PAR-2 using cells expressing PAR-2 in a culture containing inositol.