The present invention provides an allergen inhibitor which effectively prevents allergens from reacting with specific antibodies, mitigates the allergic symptoms or prevents appearance thereof, and is less likely to cause unpredictable discoloration and discoloration under usual conditions. The allergen inhibitor of the present invention comprises an allergen-inhibiting compound including a linear polymer having at least one of substituents represented by the formulas (1) to (3) at a side chain. Thus, the allergen inhibitor of the present invention shows excellent allergen-inhibiting effects.