Milk powder allergy usually appears in about 3 days, some may take several months, there is no specific standard time. In the case of fast-onset allergies, symptoms can appear as early as 2 hours after feeding. Milk powder allergy often manifests itself as red spots, papules, itching and other symptoms on the skin, some of which can be accompanied by diarrhea, vomiting and even growth retardation. After feeding, babies may refuse to drink, cry abnormally, etc. There are significant individual differences in how long it takes for allergy symptoms to appear after formula feeding, which should be judged by the amount of formula, the length of feeding time and the individual’s constitution. In general, the allergens contained in milk powder can be fully absorbed by the body in about 1-2 days, so milk powder allergy symptoms usually occur in about 2-3 days. If there is a serious allergy, such as red spots all over the body or shortness of breath or difficulty, the baby should be immediately sent to the pediatric emergency room. Once your baby has symptoms of milk powder allergy, you should immediately stop eating it, go to the hospital, improve the relevant examination and actively treat the symptoms.