Babies generally start adding supplementary food between four to six months old. Some children may exhibit symptoms after introducing additional foods, which resemble those caused by allergies. These symptoms primarily appear on the skin, in the oral cavity, digestive tract, and respiratory tract. They might present in one area or multiple areas. The most common symptoms include constipation, bloating, vomiting, diarrhea, and pain. Additionally, manifestations on the skin can include eczema, severe cases may develop urticaria or other types of allergic dermatitis.