Cow's milk (CM) allergy, one of the major food allergies with a prevalence of 2%-3%, 1,2 accounts for 21% of food-induced anaphylaxis in the UK. 3 In Japan, CM is the second most common cause of food allergy in children. Although about 50%-90% of children with childhood-onset CM allergy acquire tolerance by school age, 4,5 children with severe CM allergy that have high CM-specific immunoglobulin E (sIgE) levels and a history of anaphylaxis often have persistent CM allergy. 4,6