Final answer:
PPD and allergy skin tests are used to identify type I hypersensitivities, with results guiding diagnosis and treatment. Desensitization therapy can be employed to build tolerance to known allergens, shifting the immune response away from hypersensitivity.
Step-by-step explanation:
The PPD (purified protein derivative) test and allergy skin tests are diagnostic tools used to identify certain hypersensitivities, including type I allergic reactions. In a puncture skin test (PPST), allergens are introduced through superficial skin, typically on the patient's back or arms, to observe for a wheal-flare reaction. This reaction consists of a raised, itchy bump and surrounding redness that signal an allergy. Intradermal tests involve injecting a small amount of allergen into the dermis with a tuberculin needle. The reaction is similarly observed for a wheal-flare response within 15-20 minutes.
Treatment for identified allergies might include desensitization therapy, which involves repeated injections of allergens. Starting with extremely dilute concentrations, the quantity of allergen in the injections is gradually increased to build up tolerance. This process is intended to shift the immune response away from type I hypersensitivity towards tolerance.
Allergists use these tests to determine the antigens responsible for allergic reactions. Positive results support the diagnosis and guide treatment, while also ensuring that care providers are ready to handle any severe allergic responses during testing or treatment.