Allergy Patch Test
Patch testing is a test procedure to diagnose allergic contact dermatitis, whereas the diagnosis of irritant contact dermatitis is based on exclusion of an allergic component. Patch test techniques for diagnosing ACD have been used for over 100 years and the present test methods are based on the established principle of using a testing material (chemical, food etc.) and a delivery device (chamber). Patch testing attempts to reproduce the allergic reaction on the normal skin on the upper back of the patient. The patches are applied and subsequently removed after 48 hours. Reactions are read after 72 – 96 hours and often, again at 7 days after removal. The diagnostic value of patch testing depends upon the choice of test substance, the vehicle, the concentration, results interpretation and patient counseling. Patch tests are comprised of materials that occur in the home, work and/or recreational environment.