Final answer:
A patch test is used to determine if a person is allergic to a specific substance, which is crucial for diagnosing type I hypersensitivities. It involves observing the skin's response to allergens, and accurate results require not taking allergy medications prior to testing. Desensitization therapy is a treatment option that aims to reduce hypersensitivity.
Step-by-step explanation:
The purpose of a patch test (predisposition test) is to determine if a person is allergic to a specific substance. In a medical context, this is particularly important in the diagnosis of type I hypersensitivities, also known as immediate hypersensitivity reactions. Allergy skin testing, such as the pri_ck puncture skin test (PPST) or intradermal test, is used to identify the antigens that provoke an allergic response. These tests involve either superficial skin pri_cks or the injection of a small amount of allergen into the dermis and are observed for 15-20 minutes for a wheal-and-flare reaction, which indicates an allergy to the substance.
The importance of avoiding allergy medication prior to such testing is to ensure an accurate response; medications may suppress the immune response, leading to false-negative results. Desensitization therapy may be used to treat hypersensitivities, involving repeated injections of allergens to gradually reduce the immune system's reaction. The goal of these therapies and tests is to accurately identify allergens and reduce the patient's sensitivity to them, potentially preventing allergic reactions.