An antiallergic agent which contains as an active ingredient a thelephoric acid compound represented by the general formula (I) (wherein R<1>, R<2>, R<3>, and R<4> each independently is hydrogen, C1-4 alkyl, acetyl, or benzoyl) or a salt thereof, a compound of the thelephoric acid compound or salt with a protein, or a fraction derived from a basidiomycete belonging to the genus Gleophyllum.