Allergy testing in children
If the doctor suspects in allergic reaction allergy testing should be done. It was believed that in children under three years of age allergy testing are irrelevant. It is now known that even infants can demonstrate skin sensitivity to different food allergens in testing and that is no justified need for delaying the testing.
Important note: antihistamines should not be taken for at least 7 days before the testing, because medications can affect (anulate) test results.
Prick test is the most performed test in case of food and inhalation allergies (pollen, dust mites, feathers, animal hair). Prick or skin prick test is used for testing early hypersensitivity mediated immune response by confirming presence of IgE (immunoglobulin E) in the skin responsive to a particular allergen. Testing is performed in two phases: 1) positive (histamine) and negative control (buffer), which is read after 10 minutes and 2) applying droplets of desired concentrated allergen on the inside of the forearm pierced then with a plastic lancet. The reaction is observed after 20 minutes. If there is a positive reaction at the injection site a slight swelling wheal) will appear.
Atopy patch test is a good method for delayed allergic reaction detection to food. Testing is usually performed in infants with atopic dermatitis to assess the existence of delayed cellular hypersensitivity to food. This test is often indicated in cases of unclear gastrointestinal disturbances in children.
Testing patches with food allergens (most often: cow’s milk, egg, soy, wheat and peanuts) are taped on clear skin, usually on the back. Reaction is then followed after 48 h and 72 h. In case of a positive reaction to an allergen on contact site occurs edema, redness with tiny bubbles filled with clear liquid. A positive findings in the atopy patch test often correlates with gastrointestinal symptoms associated with food allergies.
Patch test on contact allergens is used for testing delayed hypersensitivity reaction to contact allergens. The test is performed on the skin of the back with patches consisting allergens (a standard set of 26 allergens. Test reaction is followed after 48 and 72 hours. In case of a positive reaction to an allergen in a place of contact occurs edema, redness with tiny bubbles filled with clear liquid.