Patch tests are used to help diagnose a child’s suspected allergies. Different than a blood test in which blood is drawn, actual food is used to test how a child’s body reacts to its presence. The foods chosen based are based on diet, history of previous reactions and prior skin testing results. Typically, foods are prepared by pureeing them and placing them in small metal chambers that are securely taped to the child’s back so that they are in contact with the skin. The chambers are left in place for 48 hours and must stay dry. Some children may experience discomfort from the tape or food in the chambers due to irritant reaction from the tape or from a reaction on the skin from the food. Antihistamines can be used for itching and will not affect the results of the patch test.
After 48 hours, the patches can be removed at home. After 72 hours from the placement of the patches, the patient will return to the office to have the results read by the allergist. The skin is examined for any reaction. While a reaction to the skin test doesn’t always mean that the patient is allergic to the specific allergen, it does provide us with a guide for foods that may be causing the child’s EoE.
Patch test appointments should be made prior to leaving the child’s first clinic appointment by speaking with the nurse or front desk. While scheduling the appointment, it is important to keep in mind that the test will require two visits—one to administer the patches and the other to read the results 72 hours later.