What is allergy skin testing?

Allergy skin testing is a common way to test for different types of allergies including food and environmental allergens. During an allergy skin test, a small scratch is made on a child's forearm, upper arm or back, and introduces a very small amount of a potential allergen, such as peanut protein, into the top layer of the skin. Redness or swelling at the test site indicates your child may be allergic to that substance.

Allergy skin testing can detect common allergens such as:

• Animal dander (small flecks of skin shed)
• Dust mites
• Specific foods such as peanuts, eggs, milk and soy
• Insect venom from bites or stings
• Latex
• Mold
• Pollen
• Penicillin

Why your child might need allergy skin testing

Your child’s provider may order allergy skin testing if your child has symptoms of allergies, such as coughing, itchy or watery eyes, wheezing and diarrhea. The skin test can help identify which potential allergens are causing your child’s symptoms, allowing you and your doctor to take steps to manage the allergy.

Allergy symptoms can vary by the type of allergen. For example, symptoms to airborne substances such as pollen, pet dander, and dust mites may include sneezing, stuffy nose and coughing. Symptoms to food, medicine or insect venom may include wheezing, trouble breathing, vomiting and diarrhea. 

What to expect from allergy skin testing

During the test, a very small amount of an allergen along with 2 controls are placed onto the skin, then gently pricked a two-pronged needle. The positive control, histamine, should cause a small bump while the saline control should cause no bump to ensure that the test is reliable. The areas tested are evaluated 10 minutes later.  A small hive may suggest an allergy to food or environmental allergen being tested.

Your child may be tested for more than one allergen at the same time.

For environmental allergens, there is a chance of false negatives with skin testing. If the test is negative, your child’s doctor may recommend an intradermal test, in which a needle is used to inject a small amount of allergen into the skin. Intradermal testing is not recommended for foods. For food allergens, it is important to know that there is a high chance of false positives. Your provider will talk with you more about how these tests are interpreted.

How to prepare your child for allergy skin testing

Tell your child’s allergist about any medications your child is taking, including over-the-counter medications. In most cases, your child's provider will instruct your child to stop taking antihistamines for several days before the test so it does not interfere with test results.

Risks of allergy skin testing

The most common risk of skin testing is that raised, itchy bumps will appear at the test sites, indicating a possible allergy to those substances. You can use a mild cortisone cream to ease itching. In very rare circumstances, a more serious reaction can occur, which is why it is important that testing be done in a controlled setting with quick access to medical care.

After allergy skin testing

After the test, your child may have mild itching or irritation at the testing site. If discomfort last more than a few days, talk to your child's doctor.

If an allergy has been identified, your child's doctor will work with you and your child to determine next steps and possible treatment.