Scratch/Prick And Intradermal Testing For Allergy Diagnosis- Allergy/Immunology
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Scratch/Prick Test and Intradermal Test are types of skin tests to diagnose any type of allergy. These tests are not very invasive and they provide quick results.
What to expect before the test?
Patient should inform doctor about any use of medications as some medicines may affect the results.
- Scratch/Prick Test: It is also known as skin prick test (SPT). During this test, a small drop of the possible allergen is dropped on the skin. Next, the doctor would lightly prick or scratch patient’s skin with a needle through the drop.
- After 15 minutes, the site is observed. If the patient is sensitive or allergic to the substance, there will be redness, swelling and itching at the test site. Patient may develop a “wheal,” or raised, round area, that appears like a hive. Generally, the larger the wheal, the more likely the patient allergic to the allergen.
- A positive skin test only indicates the patient is sensitive to that particular substance. It does not by itself diagnose an allergy or predict the severity of an allergic reaction. If scratch test is negative, patient is not allergic to the substance.
- Intradermal Skin Test: If the results of the scratch test are negative, an intradermal skin test is done. During this test, a tiny amount of allergen is injected into the outer layer of skin. After a specific time, the test site is observed for any redness, swelling, itching, or any other type of allergic reaction.
What to expect after the tests?
Patient may be asked to use a mild cortisone cream to ease itching. After the tests are done, patient can go back to the normal day to day routine. If the patient is allergic to substance, he/she would be asked to avoid that particular substance.