Preparing for the test:
The administration of oral corticosteroids, and application of topical corticosteroids to the test area (upper back), must be ceased two weeks prior to patch testing, and continue to be avoided for the duration of the patch test and review period. This is important as such pharmacological treatments may suppress or alter a positive reaction, and interfere with accurate test interpretation
How the test is applied: Patch testing involves applying small amounts of various allergens onto small squares on a larger patch, and the adherence of the patch or patches onto the skin. Patches are typically placed on an individual’s back and worn for 48 hours. The test area is usually examined for signs of an allergic reaction at 48 and 72-96 hours following initial patch application.
At the Australian Allergy Centre we use Chemotechnique patches and the Australian Baseline Series to test for the most common causative agents of contact dermatitis. Substances tested include nickel, fragrances, parabens and a range of other allergen components commonly found within jewellery, metal, cosmetics, skin care products, soaps, fragrances, hair shampoos, conditioners and dyes, topical medications, creams and ointments, adhesives and bandages, fabrics, inks, household disinfectants and industrial products, and other everyday materials.
What’s a positive reaction: A positive reaction generally becomes red and itchy at the test site. Swelling or a small fluid-filled blister may develop. Positive reactions usually become apparent by 72-96 hours. Occasionally reactions can take longer to develop – up to two weeks.