An agent for use in a method for the prevention and / or treatment of an allergic disease selected from polyinosis, allergic rhinitis, allergic conjunctivitis, atopic dermatitis and asthma, comprising a low molecular weight polysulphated hyaluronic acid derivative represented by the general formula (IA) or (IB) below, or a pharmaceutically acceptable salt thereof as active ingredient: ** Formula ** where n represents a number from 0 to 15； X represents the following formula (a) or (b)； ** Formula ** Y represents the following formula (c), (d) or (e)； ** Formula ** each R independently represents a hydrogen atom or a SO3H group, provided that SO3H groups represent 80 to 100% of the total number of R； R1 represents -OH, -OSO3H or -NZ1Z2, where Z1 and Z2 each independently represent a hydrogen atom, -SO3H, an optionally substituted C1-6 alkyl group, an optionally substituted aryl group, an optionally substituted aralkyl group or a group optionally substituted heteroaryl, or -NZ1Z2 collectively represents an amino acid residue or a peptide residue； and each * represents a binding site with an oxygen atom； ** Formula ** where n represents a number from 0 to 15； W represents the following formula (f) or (g)； ** Formula ** each R independently represents a hydrogen atom or a SO3H group (provided that the SO3H groups represent 80 to 100% of the total number of R； R1 represents -OH, -OSO3H or -NZ1Z2 (where Z1 and Z2 each independently represent a hydrogen atom, -SO3H, an optionally substituted C1-6 alkyl group, an optionally substituted aryl group, an optionally substituted aralkyl group or an optionally heteroaryl group substituted or -NZ1Z2 collectively represents an amino acid residue or a peptide residue； and each * represents a binding site with an oxygen atom.Un agente para su uso en un método para la prevención y/o el tratamiento de una enfermedad alérgica seleccionada entre polinosis, rinitis alérgica, conjuntivitis alérgica, dermatitis atópica y asma, que comprende
