What is the main purpose of patch testing in allergy assessments?

The primary purpose of patch testing in allergy assessments is to detect delayed allergic reactions. This method is specifically designed to identify contact dermatitis and other types of delayed hypersensitivity reactions that occur hours to days after exposure to an allergen.

During patch testing, small amounts of potential allergens are applied to the skin and left in place for a specific period, typically 48 hours. After this time, the skin is evaluated for reactions, which may not appear until days later. This contrasts with other testing methods that are geared toward identifying immediate allergic responses, which occur quickly after exposure, typically within minutes to hours.

While patch testing is effective for assessing reactions to substances like metals, fragrances, and preservatives, it is not used for diagnosing food allergies or environmental allergies, which are typically evaluated through different methods such as skin prick tests or serological tests.