When conducting patch testing for allergens, how many hours after application is the skin assessed for reaction?

When conducting patch testing for allergens, the skin is typically assessed for reaction 48 hours after application. This time frame allows sufficient time for the immune response to develop in individuals who may be allergic to the substances tested. The 48-hour mark is essential because many allergic reactions, particularly delayed hypersensitivity responses, take time to manifest. Evaluating the skin at this interval provides a more accurate assessment of potential allergy to the applied substances, as reactions may not be immediately visible and can take several days to appear fully.

While other time frames may be relevant in different contexts of medical assessments, 48 hours is the standard procedure specifically for patch testing to ensure reliable and valid results.