Penicillin in milk--its importance in urticaria.

Fifty patients with recurrent urticaria were tested by means of the RAST test for penicillin allergy. Fifteen patients had positive reactions and of these, thirteen received provocation tests with 0.1 U/ml of penicillin in milk. Four had definite positive reactions, three doubtful reactions and six had no reaction. Although there has been improvement in the purity of milk, penicillin residues remain a potential cause of urticaria even in very low amounts and could have contributed to the urticaria in at least 8% of our patients. Veterinary use of antibiotics and food quality should be strictly regulated to prevent contamination of our diet.