A: Food allergies are a common concern. They affect 3-6% of children, although many infants and toddlers outgrow their food allergies by age 5 as their immune and digestive systems develop. Since allergies are usually an inherited condition, it’s more likely for your child to have a food allergy if allergies, asthma or eczema run in the family.

Signs of food allergies include skin rashes such as hives (red welts) and eczema (scaly patches), vomiting, diarrhea, and nasal congestion. Rarely, a child might have a severe reaction called “anaphylaxis”: with difficulty breathing and loss of consciousness.

When your baby developed his rash, it’s best to contact your pediatrician to make the diagnosis and tell you what to do. It’s impossible for me to diagnose your baby’s rash by your description, but it sounds like it might not be a food allergy. Generally, symptoms of a food allergy usually appear within an hour of eating the offending food and disappear within 24 hours. Skin rashes can also result from insect bites, skin infections, illnesses, sensitivity to soap or detergent, allergies to medications, and other causes. Many rashes come and go on their own without any treatment, without causing any problems, and without you ever figuring out what caused it.

It sounds like you’re following most of the recommendations to help prevent food allergies: breastfeeding instead of formula feeding; waiting until your baby is 4-6 months of age to start solid foods such as cereals, and pureed fruits and vegetables; and starting one new food at a time for a few days to observe for allergies. 90% of childhood food allergies are caused by six foods: cow’s milk, eggs, soy, wheat, peanuts, and tree nuts (walnuts and almonds). So it’s also important to hold off until your baby is 12 months old to give foods that commonly cause allergies: cow’s milk, egg whites, peanut butter, plus citrus fruit and strawberries and shellfish.