What is the purpose of a patch test in dermatology?

The purpose of a patch test in dermatology is to determine if a substance causes an allergic skin reaction. During this test, small amounts of various allergens are applied to the skin, typically on the back, under adhesive patches. The skin is then monitored for any signs of an allergic response, such as redness, swelling, or itching, usually observed within 48 to 72 hours after application. This method is essential for diagnosing contact dermatitis and identifying specific triggers that can lead to allergic reactions, enabling better management and avoidance strategies for patients with sensitivities.

The other options focus on different aspects of skin health and are not related to the specific purpose of a patch test. Evaluating skin hydration levels, checking for fungal infections, and assessing blood circulation involve different methods and tests tailored to their respective concerns, rather than the identification of allergic reactions.