Allergy Skin Tests - How They're Performed
Allergy Skin Testing
Allergy skin testing can pinpoint the cause of an allergy and is an important tool for diagnosing one. Learn how allergy skin testing works.
By Krisha McCoy
Medically Reviewed by Christine Wilmsen Craig, MD
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If you have symptoms of an allergy, your doctor may recommend that you have an allergy skin test. Allergy skin testing allows your doctor to determine exactly what substances you are allergic to as well as those you are not allergic to. This information helps in developing your allergy treatment plan.
When Is Allergy Skin Testing Recommended?
Allergy skin testing can be used in both children and adults when an allergy is suspected. To determine whether you need to undergo allergy skin testing, your allergist will talk with you about your symptoms, closely review your medical history, and perform a physical exam.
Symptoms that signal you may need allergy skin testing include:
- Itching of your eyes, nose, throat, and skin
- Runny nose
- Nasal, sinus, or chest congestion
- Watering eyes
- Anaphylaxis (a severe, life-threatening allergic reaction that affects your entire body)
- Abdominal cramping and diarrhea after eating certain foods
- Extreme reaction to insect stings
Allergens and Skin Testing
Allergens are generally harmless substances (usually proteins) that your body's immune system overreacts to, resulting in allergic symptoms.
Allergens that are used in allergy skin testing include:
- Dust mites
- Pet dander and hair
- Stinging insect venom
- Natural rubber latex
- Food components
How Allergy Skin Testing Works
For an allergy skin test, your doctor will introduce a small amount of a suspected allergen into your skin and observe how your body reacts. If you are allergic to the substance, your body will launch a mild allergic reaction that results in skin symptoms that your doctor will be able to detect.
Types of allergen skin tests include:
- Skin prick test.A skin prick test is a convenient and inexpensive test. A drop of solution containing the allergen is placed on your forearm or your back. A sterile needle is passed through the drop and pricks the skin. This introduces the allergen under your skin. Fifteen minutes after the allergen is introduced, your doctor will evaluate the area of your skin to determine if you have had a reaction, which indicates that you are allergic to the substance. A "reaction" is a slightly swollen, sometimes itchy, hive-like bump that will usually disappear within 30 minutes. Skin prick tests can be used to test for a variety of allergens at once.
- Intradermal skin test.Intradermal allergy testing is similar to a skin prick test, but instead of a needle prick, the allergen solution is injected under your skin with a syringe. The doctor will look for the same kind of skin reaction as in a skin prick test. Intradermal skin testing is primarily used to test for venom and antibiotic (penicillin) allergies.
- Scratch test.Scratch tests, which are rarely used today, work the same way as skin prick and intradermal tests, but involve making a scratch in your skin and dropping the allergen into the scratch.
Allergy skin testing is relatively painless and has a low risk of side effects. Very rarely, severe allergic reactions (for example, anaphylaxis) have been reported as a result of food allergen skin testing.
Allergy skin tests aren't always accurate, especially in people who are taking antihistamine medications, those who are being tested for food allergens (rather than inhaled allergens), and people with eczema or another skin condition that makes the results of allergy skin testing difficult to read. In addition to allergy skin testing, your doctor may perform other tests (for example, blood tests, food challenges, bronchial or nasal provocation tests, nasal smears) to confirm the presence or absence of an allergy.
Allergies are no fun, especially when you don’t know what’s causing them. With a series of tests, you may be able to pinpoint the cause and breathe easier.
Video: Skin Prick Test (Allergy Test) - John Hunter Children's Hospital
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