More or less the same clues point to food allergies in children as in adults, although food allergies affect many more children than adults. Most kids outgrow their food allergies by the time they're four or five. When kids eat something they're allergic to, their immune systems overreact and send out antibodies called immunoglobulin E. The antibodies then trigger the mast cells, which cause the production of a bunch of chemicals in the body, one of which is histamine. Histamine causes the symptoms that signal food allergies. Such signs include vomiting, diarrhea, asthma, cold-like symptoms of a runny nose and itchy eyes, coughing, hoarseness and stomach cramps. In some cases, a child will develop eczema or a skin rash when he eats a food he's allergic to. In rare cases, a life-threatening condition called anaphylaxis can set in.
To get a better idea if these signs actually point to a food allergy, pay attention to the symptoms: when they occur and for how long. The most common foods that kids are allergic to are milk, eggs, shellfish, peanuts, soy, wheat and tree nuts. If the symptoms set in shortly after your child eats any of these items, there's a likely chance allergies are involved. However, food intolerance can often resemble food allergies, but it's caused by digestive issues and not immune system issues.
If you notice signs of a food allergy, your doctor can assist in diagnosis. He'll ask for a history of your child's suspected allergy and whether any other family members have allergies. He might also do a skin or blood test. The skin test introduces minute amounts of purified allergens to your skin to see whether you react or not; if you do, you probably have allergies. The blood test is done at a lab where technicians check your child's blood to see whether it produces antibodies when certain allergens are mixed in.