The present inventionis related to field of allergic(hyper--sensitivity) diseases and provides amethod for producing modifiedaller-genic polypeptides for use inim-munotherapies. In the method of theinvention, said allergenicpolypep-tides are modified so that they are notcapable to form transient dimers. Theinvention also provides modified.beta.--lactoglobulins for use inimmunother-apy of milk allergy.