Skin Allergy Test

©Fort Belvoir Community Hospital | Flickr.com

©Fort Belvoir Community Hospital | Flickr.com

A skin allergy test is a method used to help identify the trigger allergen causing allergy symptoms. This method is done by placing an extract of the allergen on the skin by topical patch, scratch, prick, or injection to see if the body will respond to the allergen with a localized reaction, such as itching or redness.

Why would I need a skin allergy test?

Skin allergy tests may be recommended by an allergist if you are experience allergy symptoms, have had a severe or anaphylactic reaction to an allergen, or have a family history of allergies. While there are different types of allergy tests, the most common choice by allergists is a skin allergy test.

What are the different types of skin allergy tests?

A skin allergy test is looking for allergies to: Pollen, dust mites, molds, pet dander, and foods. Skin allergy testing is not a painful procedure and usually results in only temporary, minor discomfort. The most common forms of skin allergy tests are:

  • Scratch, puncture, or prick test. In this method the allergist would drop an extract of the potential trigger allergen on the skin and then “scratch” the skin with a disposable pricking device. The scratch of the device allows the allergen to enter the superficial or top layer of the skin. This test is usually done on the arm or back and produces a reaction within approximately 15-20 minutes. In this type of test several potential allergens are all tested at the same time.
    • Prick-Prick test. This test “pricks” a fresh fruit or food allergen and then immediately scratches the skin in the same manner as the “scratch” test. Someone with oral allergy syndrome may not react to an extract of the food allergen in a typical “scratch” test because it is caused by a cross reaction with pollen. Therefore, the prick-prick test may be recommended for people with oral allergy syndrome because it could show a reaction to a food due to a cross-reaction
    • Intradermal test. In this method an extract of the potential allergen is injected under the skin like a TB (tuberculosis) test. This is done with a syringe and small needle. The allergist will then evaluate the site of injection for a reaction such as redness and swelling. This test is more sensitive than the “scratch” test with more frequent positive results though it has an increased chance of false-positive results. Intradermal testing is usually done if further testing is required to identify if there is an allergy to a specific medications or insect venom.
  • Patch test. This method places the allergen extract on a patch which is then placed on the skin. Patch test is to identify the allergens that cause reactions to the skin such as a rash. The patch test is the only test that cannot be done in the office. The patch is placed by the allergist and worn for approximately 48 hours. The patch is then removed and evaluated by the allergist in 72-96 hours for a reaction.

These tests are done by appointment only in your allergist’s office. If you have an appointment for a skin allergy test, make sure to ask how long it will take and plan accordingly. It is possible for the test to take an hour or longer.

What happens if my skin allergy test shows I have an allergy?

If your skin allergy test shows you are allergic to an allergen you will have a positive test result. A positive result would be to have a reaction where the extract touched the skin such as a red, raised bump. The size of the bump will also show the allergist how allergic you are to the allergen. In some cases, the reaction could begin to itch, turn red and swell, or progress to a more serious allergic response such as an anaphylactic reaction. After diagnosis you and your allergist should discuss how to treat your allergy as well as a “plan of action” in case of an unexpected exposure.

Is there any reason I can’t get a skin allergy test?

In some cases your allergist may not allow you to take a skin allergy test and would recommend a blood test or oral challenge. Reasons may include:

  • If you are unable to stop the medications requested by your allergist (such as some heart medications).
  • Cannot tolerate the required scratches or pricks.
  • Have an unstable health condition.
  • Have poorly controlled asthma or a severe skin condition such as eczema or psoriasis.
  • History of a severe allergic reaction or anaphylactic response to an allergen.

 

References

Disclaimer: The information contained in this site is for educational purposes only, and should not be used as a substitute for a licensed physician. Please see your physician for diagnosis and treatment of any concerning symptoms or medical condition. Click here to read the full disclaimer.
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