Patch testing is a diagnostic tool used to identify delayed allergic reactions (contact dermatitis) caused by substances such as metals, fragrances, preservatives, and topical medications. Small amounts of allergens are applied to adhesive patches and placed on the back for 48 hours. The skin is then evaluated over several days to detect reactions. This test is especially useful in diagnosing chronic or unexplained rashes and guiding patients in avoiding specific contact allergens.
