GP Information: Dermatology Department
Patch Tests
Patch tests are invaluable in detecting the allergens responsible for allergic contact dermatitis (lymphocyte mediated allergic reaction). Standard dilutions of common allergens are applied to the back under aluminium discs. The discs are left in place for 48 hours and read at 48 hours and 96 hours
The most important part of the investigation is the history to ensure the correct allergens are applied in correct concentrations. Interpretation requires skill and experience. A positive result does not prove that it is relevant to the present episode
