How Do Skin Allergy Tests Work?

A Healthier Michigan

| 3 min read

Skin allergy tests can help care teams determine what allergies or sensitivities a patient may or may not have, based on the reactions and results to the test. Allergic reactions are an immune response, which is usually meant to attack foreign infections or substances in the body.
Allergies range from Type I to Type IV sensitivities, with the reactions ranging from irritation or aggravation to anaphylactic shock, a life-threatening reaction. According to Medline, published by the National Library of Medicine, skin allergy tests are generally performed for Type I sensitivities or allergies, and not food allergies or higher type allergies, since these are more likely to induce anaphylactic shock.
A skin allergy test introduces small amounts of a variety of possible irritants or allergens and tests the body for an allergic response. There are a few ways these tests can be performed if the care team or patient has reasons to suspect an unknown or undiagnosed allergy. Skin allergy tests along with other diagnostic tools can help to determine allergy treatment plans or advise avoidance, according to the Mayo Clinic.

Why skin allergy tests are given

Primarily the reasons to give a skin allergy test are to determine the cause of an allergy, the severity, and what treatment plans might address the allergy properly, according to the Mayo Clinic. There are many allergies and skin conditions that can be aided in diagnosis from a skin allergy test, including:
  • hay fever
  • allergic asthma
  • eczema
  • food allergies
  • penicillin allergies
  • bee allergy
  • pet dander allergies
  • skin mite allergies
Skin allergy tests introduce minimal amounts of allergens and are safe for the majority of adults and children, according to the Mayo Clinic, and typically the most dangerous or Type IV allergens are not tested with skin tests. Let your care team know if you have ever had an allergic reaction, especially a severe reaction, or if you have any existing skin or respiratory conditions. Some conditions and medications might interfere with skin allergy tests.

How are skin allergy tests given?

There are three main types of skin allergy tests: skin prick tests, intradermal skin tests, and patch tests. All have the same goal of diagnosing or identifying allergens, but they are performed a little differently.

Skin prick or scratch allergy test

Skin prick tests, scratch tests, or blood tests are the most common type of skin allergy test, according to the Cleveland Clinic. Some allergens are tested with a skin prick with the allergen, which will result in a small allergic reaction on the skin if allergic. If it is a scratch test, allergens will be placed on the skin which is then scratched, allowing the allergens to enter and cause a reaction if the patient is allergic.

Intradermal skin allergy test

An intradermal skin allergy test involves multiple allergens being injected into the epidermis, the outside layer of the skin. This is more common for medication allergies or if the skin prick test is inconclusive, according to the Cleveland Clinic.
If the test is positive, you are allergic, but if negative you may need a second round of intradermal testing. The test is not painful for most patients, according to the Cleveland Clinic.

Patch test

A patch test uses patches with allergens on them, placed onto your skin to illicit an allergic reaction like a prick or scratch test, but through contact from the patch on the skin. This test helps diagnose contact dermatitis, or allergies or sensitivities to skincare products, plants, or other skin irritants.

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