The invention relates to a free glycine source for use in inducing tolerance against an allergen, or preventing the development of allergy in a human or other mammal. The invention further relates to a composition comprising protein, fat and carbohydrates with at least 7 en % protein and at least 60 mg free glycine source per gram protein, preferably at least 70 mg glycine per gram protein. The free glycine source is preferably the free amino acid glycine, a salt of the free amino acid glycine, or a combination thereof； the protein can be intact protein, hydrolysed protein, peptides, free amino acids, salts of amino acids, or combinations thereof.
