An allergic reaction is usually mild, causing hives or whelps (urticaria) and itching. Hives are large red areas that are raised and usually come and go over four to six hours, disappearing in one area and popping up in another. Hives usually only last a few days, but may last weeks, even if your child is not being exposed to what he is allergic to anymore. You can use an over the counter antihistamine, such as Benadryl to treat hives.

A more serious type of allergic reaction, anaphylaxis, can be life threatening. Children with anaphylaxis will have trouble breathing, with wheezing and difficulty catching his breath, difficulty swallowing, may feel scared and weak and will usually have hives and swelling. If your child is having these symptoms, you should activate your local emergency services. Children who have had an anaphylactic reaction should always have an EpiPen or EpiPenJr available.

It is not always possible to find out to what your child is allergic, but if you know what your child is allergic to, then you should avoid it.