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Type I Hypersensitivity Reaction

Type I Hypersensitivity Reaction

What is allergy skin testing? — Allergy skin testing is testing that helps your doctor figure out what you are allergic to.
What happens during skin allergy testing? — Doctors use 2 main types of allergy skin tests. The most common is called a skin prick test. The doctor puts a drop of the substance you might be allergic to on your skin and makes a tiny prick through the drop into your skin. If you are allergic to any of the substances, itchy red bumps usually show up within 15 to 20 minutes. The bumps go away within an hour or so.
If your skin does not turn red and bumpy during the skin prick test, your doctor might still think you could be allergic to the substance. He or she might inject a tiny amount of the substance under your skin. This is called an "intradermal" test. Intradermal tests are slightly better at showing an allergy because more of the test substance gets into the skin. Because this is a stronger type of test, it can sometimes cause allergic reactions, and it is not done for some types of allergies, such as food allergies.
The pricks or injections are done on your arms and sometimes on the upper part of your back. This is not painful, but small children might find it upsetting. You might get tested for a few different substances at the same time.
Why do I need allergy skin testing? — Your doctor might recommend allergy skin testing if you have symptoms that seem to be caused by an allergy. The table shows common types of allergies and their symptoms (table 1).
If you know exactly what is causing your allergies, you can avoid those substances and choose the best treatment.
How do I prepare for allergy skin testing? — Your doctor might tell you to stop taking certain medicines (such as allergy medicines) for up to 1 week before you get an allergy skin test. This is because some medicines can block the skin test reaction, making the test results appear normal even if you actually do have an allergy.
All topics are updated as new evidence becomes available and our peer review process is complete.
This topic retrieved from UpToDate on: Mar 30, 2020.
Topic 86636 Version 5.0
Release: 28.2.2 - C28.105
© 2020 UpToDate, Inc. and/or its affiliates. All rights reserved.

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