Food allergies are more common in children and babies than they are in adults. The three most common foods that cause allergies in babies are cow’s milk, soy milk, and eggs. In older children, the most common allergens are peanuts, tree nuts, fish, shellfish, and wheat. Some food allergies tend to be outgrown, like cow’s milk, soy milk, and egg, but others like peanuts and tree nuts tend to be more permanent.