The most common food allergy in children worldwide is cow's milk allergy. The most known allergens from cow's milk proteins are casein, alpha-lactalbumin, and beta-lactoglobulin. Lactalbumin hydrolysate is used as a stabilizer in the measles mumps rubella (MMR) vaccine originating in India. Different commercial forms of the MMR vaccine are available. While neomycin is used as a stabilizer in one form, lactalbumin hydrolysate is used in the other form. We present a patient who was followed up for cow's milk allergy and developed anaphylaxis after the MMR vaccine originating from India. A 4-year-old girl with a history of anaphylaxis with cow's milk whose vaccinations were applied by the routine vaccination schedule in the family health center. Sneezing and coughing started 1 minute after vaccination. The patient presented to the emergency department (within 10 minutes after vaccination) with severe respiratory distress and intercostal retractions. Three doses of intramuscular adrenaline, 5 minutes apart, intravenous pheniramine and methylprednisolone, and inhaler short-acting beta agonist were administered to the patient. Symptoms regressed approximately 40 minutes after hospitalization. In our patient with a history of cow's milk anaphylaxis and lactalbumin-specific immunoglobulin E value of 61.3 kU/L, anaphylactic reaction with MMR vaccine seems to be related to the lactalbumin contained in the vaccine. Families and physicians should be meticulous about reading labels in the follow-up of patients with known food allergies.