The present invention pertains to novel strains of lactic acid bacteria capable of reducing an individual's tendency to react allergic against a variety of different allergens. In particular, the present invention relates to recombinant strains of lactic acid bacteria that express surface polypeptides which include peptides or antibody fragments acting as mimic for at least a part of the F.sub.c region of IgE-molecules. The invention also pertains to food or pharmaceutical compositions containing said micro-organisms or active fractions thereof.