Final answer:
A patch test is also known as a PPST and is used to identify potential allergic responses, particularly type I hypersensitivities. It is a widely accepted diagnostic method characterized by a wheal-flare reaction after introducing an allergen extract to the skin.
Step-by-step explanation:
The PPST is widely regarded as a convenient and economical method to diagnose allergies, endorsed by the US Joint Council of Allergy and the European Academy of Allergy and Immunology. If a wheal, which is a raised, itchy bump, and flare, which includes the redness around the wheal, appear within minutes after the application of the allergen, this indicates a type I hypersensitivity. The size of the wheal-flare reaction correlates with the degree of the patient's sensitivity to the particular allergen.