Background: Cow's milk is one of the most common of the foods that cause food allergies in children. Here, we present a 10-month-old male who was diagnosed with having an allergy to cow's milk and who developed an anaphylactic reaction after being recently vaccinated with a measles vaccine. Case: The patient had been diagnosed with atopic dermatitis and cow's milk allergy at 40 days old after a rash appeared on his face and arms while exclusively breastfeeding. At 9 months, on his routine welfare outpatient appointment, he developed a facial rash and swelling, wheezing, difficulty breathing, and cyanosis within 10 min of having his first measles vaccination (M-VAC (R); Serum Institute of India, Hadapsar, Pune, India). After an allergy evaluation and a physical examination that showed that he was otherwise healthy, he was diagnosed with an allergy to cow's milk, which was then eliminated from his diet. Laboratory evaluations were as follows: serum immunoglobulin E (IgE) to cow's milk: 36.2 kU/L, alpha-lactalbumin: 9.39 kU/L, beta-lactoglobulin: 8.74 kU/L, casein: 34.2 kU/L, latex-specific (sp)IgE: 0.10 kU/L, gelatin spIgE: <0.35 kU/L (normal levels <0.35 kU/L; Pharmacia, Uppsala, Sweden). Results revealed lactalbumin hydrolysate as one of the M-VAC ingredients according to the manufacturer's package insert. Conclusion: In most cases with a cow's milk allergy, vaccines are administered without any problems because the amount of milk proteins contained in the vaccines is not sufficient to represent a risk factor for anaphylaxis; however, the vaccine content should be examined for possible allergens, particularly for children with food allergies, before vaccinating. We should keep in mind when determining the agent responsible for an allergic reaction that the risk from a residual component of milk protein in vaccines can differ according to the nutritional habits of the population.