A method for reducing cytotoxicity of eosinophil derived toxins comprising administering to a subject an effective amount of heparin, heparan sulfate, a potent heparanase inhibitor or a polypeptide which has sequence as follows: BZBXBX, XBBBXXBX, XBBXBX, BBXXBBBXXBB, BXBBXB, XBBBXXBBBXXBBX, or TXXBXXTBXXXTBB, wherein X represents any amino acid, Z represents an aromatic amino acid, and B represents a basic amino acid and T represents a turn.