Allergy Skin Test
Reviewed
Also called: Type 1 hypersensitivity skin test, Hypersensitivity test, Allergy scratch test, Allergy patch test, Intradermal test, Prick test or puncture test, Allergy testing
An allergy skin test helps find out what is causing your allergic reaction by exposing your skin to allergy-causing substances known as allergens.
Specimen: Not applicable; this is a procedure involving skin exposure to allergens.
Urgent safety information
If you experience symptoms of anaphylactic shock, you should inject the device into your skin and call 911.
Emergency numbers on this page are for the United States. Outside the US, call your local emergency number.
Why this test may be ordered
- To diagnose certain allergies when you have symptoms such as stuffy or runny nose, sneezing, itchy watery eyes, hives, diarrhea, vomiting, shortness of breath, coughing, or wheezing.
- To identify which substances (allergens) are causing your allergic reaction so your provider can plan treatment.
Preparation and collection
You may need to stop taking certain medicines before the test. These could include antihistamines and certain antidepressants. Your provider will tell you which medicines to avoid before your test and for how long. If you are having a patch test, your provider may want you to avoid heavy sun exposure and tanning for at least two weeks before the test.
You will most likely get tested by an allergist or a dermatologist. An allergy scratch test, also known as a skin prick test, is the most common allergy skin test. Your provider will place small drops of specific allergens on different areas on your skin, such as your forearm or back. Your provider will then lightly scratch or prick your skin through each drop.
There is very little risk to having allergy skin tests. The most common side effect is red, itchy skin at the test areas. In very rare cases, an allergy skin test may cause anaphylactic shock. This is why skin tests must be done in a provider's office where emergency equipment is available. If you've had a patch test and feel intense itching or pain under the patches once you are home, remove the patches and call your provider.
Understanding results
Test results are usually reported as positive or negative. Your provider will consider your symptoms and medical history to understand the results of an allergy skin test.
- Positive (red bumps or swelling): If you have red bumps or swelling at any testing areas, the test is positive. This means you are probably allergic to those substances. Limitation: Usually, the larger the reaction, the more likely you are to be allergic. Next step: If you are diagnosed with an allergy, your provider will recommend a treatment plan.
- Negative (no reaction): If you do not have red bumps or swelling at any of the testing areas, the test is negative. This means that you are probably not allergic to those substances. Limitation: This test is sometimes used if your allergy scratch test is negative, but your provider still thinks you might have an allergy. Next step: Your provider will consider your symptoms and medical history to understand the results of an allergy skin test.
- Common side effect is red, itchy skin at test areas.
- Very rarely, an allergy skin test can cause anaphylactic shock, a life-threatening reaction. Therefore, tests are only done where emergency equipment is available.
- A positive result indicates a higher likelihood of allergy but is not a confirmed diagnosis; your provider will consider your symptoms and history.
- A negative result indicates a lower likelihood of allergy but does not completely rule out an allergy.
- For patch tests, if you feel intense itching or pain under the patches at home, remove them and call your provider.
What to do next
If you are diagnosed with an allergy, your provider will recommend a treatment plan. If you are at risk for anaphylactic shock, you may need to carry an emergency epinephrine treatment with you at all times.
- What is it used for?
- Why do I need an allergy skin test?
- What happens during an allergy skin test?
- Will I need to do anything to prepare for the test?
- Are there any risks to the test? What do the results mean?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.