The present invention provides an allergy inhibitor using the efficacy of amorphous paramylon which is a substance obtained by changing the crystalline structure of paramylon.The present invention relates to a substance for inhibiting allergic diseases. Amorphous paramylon of the present invention is an allergy inhibitor comprising amorphous paramylon which is obtained by amorphosizing crystalline paramylon derived from Euglena, and has a relative crystallinity of 20% or lower to the crystallinity of crystalline paramylon, determined by an X-ray diffractometry. This allergy inhibitor enables efficacious inhibition of allergic diseases such as atopic dermatitis, pollinosis, and the like.