An elimination diet can help you determine the particular foods to which your child is most allergic or sensitive. Once you have identified them, you can eliminate from his diet the things that cause trouble.
Begin by eliminating foods you think may be the source of your child's symptoms. If you are not sure exactly where to start, start with the foods that most commonly cause a reaction wheat, citrus fruits and juices, nuts (including peanut butter), dairy products, corn, soy products, and eggs.
Eliminate the suspect foods from your child's diet for a two-week period. Be aware of the ingredients in manufactured food products. Many of these will probably contain ingredients that are on your list of suspects. Observe your child carefully during this elimination period. How does he feel? Does he seem to be breathing more easily? Are his eyes clear instead of itchy and irritated? Is your child generally happier and less cranky? Does he have more energy?
After the elimination period, test a food, or class of foods, by putting it back on your child's menu. For three days, observe how he reacts (it can take as long as seventy-two hours for a reaction to manifest itself). To make sure you can identify precisely which is the offending food, add only one food or class of foods every three days, and give it to your child in as pure a form as possible. For example, to test wheat, give your child cream of wheat rather than bread, which may contain other allergens.
If eliminating all suspect foods from your child's diet at one time seems too drastic, try eliminating particular classes of foods one at a time. For example, eliminate all wheat products for a two-week period and see how your child reacts. If his symptoms are not relieved, then eliminate all dairy products as well (and continue to keep wheat off the menu) for the next two-week period, and so on. Continue deleting a food or class of foods until your child's symptoms improve, and keep your child off the food throughout the entire trial. Once symptoms have improved, you can assume that your child is sensitive to the food most recently deleted. You can then add the other foods back into your child's diet, one at a time, but be alert for any sensitivity or reaction.
Once you have determined which food or foods are causing your child's reaction, simply keep them off the menu. Read labels carefully to be sure the offending foods are not present as ingredients in the products you buy.
You can also try tracking down food sensitivities by using a diet diary. For three to four weeks, write down everything your child eats and when he eats it, along with how he feels and any reactions he displays. After the four-week period, you should be able to detect patterns in your child's responses to different foods.
For a more detailed approach to uncovering food sensitivities, read Tracking Down Hidden Food Allergies by William Crook, M D. (Professional Books, 1978).