The case of a 35-year-old woman who suffered anaphylaxis after the ingestion of milk or milk-containing products is presented. Symptoms also appeared after the patient used a cosmetic which contained casein. Skin prick tests, specific IgE measurement, and immunoblotting were carried out with cow's milk extract, and its purified proteins: casein, beta-lactoglobulin, and alpha-lactalbumin. Specific IgE to cow's milk casein was detected with the three tests. Immunoblotting revealed one band of 24 kDa approximately corresponding to the beta-fraction of casein. Negative results to beta-lactoglobulin and alpha-lactalbumin were obtained with the three methods. Symptoms were controlled by rigorous dietary and behavior measures.