Food Allergy

Diagnosis

Having a child evaluated as soon as possible will identify the offending food and allow parents to eliminate it from the child's diet. Many allergists, or doctors who specialize in allergies, will do a skin-prick test followed by a blood test. The skin-prick test is a series of pricks on the child's skin with a plastic applicator that contains a single food in concentrated form. A food allergy has been identified if the child's skin reacts by welting or becoming red. The skin-prick test for foods (not for aeroallergens) has a high incidence of false positives; that is, the test may be positive but the child is not truly allergic, or does not have symptoms from the food. This test is not used on a child with severe anaphylactic reactions or on children with widespread eczema, a skin disorder.

The allergist may also do a food challenge in the doctor's office. The child is fed the suspected food in increasing amounts to see what kind of reaction occurs.

One of the tests allergists use is called the RAST (Radio-Allergo-Sorbent Test). It measures the amount of IgE antibody in the blood that is produced for certain known food allergens. Like the skin-prick test, RAST and other antibody tests have a high rate of false positives.

Some doctors will put the child on an elimination diet for one week to 10 days. The basic elimination diet is a series of foods that have proven not to be allergy triggers. This diet consists of foods such as lamb, poultry, rice, vegetables, and all fruits, except citrus and berries. One new food is introduced each week. Parents record the child's reaction to each food. If the child has no reaction, the food is considered safe and can remain in the diet. If there is a reaction, it is noted and the food is removed. The child continues the elimination diet for a few more days, at which time another food is introduced. The elimination diet is often done after skin testing, so there is a logical guide for what to eliminate.

Content licensed from:

Author Info: Janie Franz, Thomson Gale, Gale, Detroit, Gale Encyclopedia of Children's Health, 2006

This feature is for informational purposes only and should not be used to replace the care and information received from your healthcare provider. Please consult a healthcare professional with any health concerns you may have.