The photopatch test is typically conducted over several days. Hereâs a step-by-step outline of the process:
Day 1: Small amounts of test substances are applied to the skin in small patches. These patches are left in place for 24 to 48 hours. Day 2: The patches are removed. One area of the test site is exposed to a controlled amount of UV light, while the other remains unexposed as a control. Day 3-4: The test sites are evaluated for reactions. A positive reaction, such as redness, swelling, or a rash, indicates a phototoxic or photoallergic response.
