Allergy Skin Tests Help to Diagnose Allergies

The Pros and Cons of Using a Prick Test or an Intradermal Test

Sep 6, 2009
Stella Walsh

The Forearm is Often Used in Allergy Skin Testing - Stella Walsh

Even though skin tests are the most common form of allergy testing, there are both advantages and disadvantages to using this tool for diagnosing an allergy or allergies.

The very first skin test was performed in 1869. Dr. Charles Blakely put pollen into a small cut on his wrist. When a rash developed about twenty minutes later, he deduced that he was allergic to the pollen.

Except in circumstances where a skin test is not appropriate, it is usually the first choice for identifying the trigger of a suspected allergy.

Allergy Skin Tests

In an allergy skin prick test (percutaneous testing) multiple drops of extract containing possible allergens are placed on the skin. The skin is lightly pricked with a special needle to allow the extract to enter the body. After about fifteen minutes, the pricked areas of skin are checked to see if any redness or swelling has developed. The allergy specialist will measure and analyze any areas that have reacted to an allergen.

An allergy intradermal skin test (intracutaneous testing) is often used when the skin prick test does not provide answers. The extract with the potential allergy trigger is injected into the outer layer of the skin with a fine needle. Any swelling and redness that occurs is measured and analyzed. These particular skin tests are very sensitive and are more likely to give a false positive.

Advantages of Using Skin Tests to Diagnose Allergies

There are several advantages to using skin tests in the diagnosis of allergies:

Allergy skin tests are not very invasive.
Children can usually tolerate skin tests fairly well because they are relatively painless.
Allergy skin tests are considered safe.
The results of an allergy skin test are available right away.
The skin tests are highly accurate and rarely give a false negative result.

Disadvantages of Using Skin Tests to Diagnose Allergies

While allergy skin tests are the most common tool for diagnosing allergies, there are some disadvantages associated with them:

Allergy skin tests are not a good choice for a patient with a history of anaphylaxis.
The results of a skin test are not as detailed as those of a blood test.
The strength of the extract used in the allergy skin tests may vary.
Patients who have troublesome skin conditions such as eczema may find allergy skin testing too uncomfortable or painful.
Skin tests may not produce accurate results if the patient is taking medications such as antihistamines, antidepressants or certain cold medicines. Skin tests cannot be performed on people who are taking beta blockers.

A physician will look at the individual situation for each patient and weigh the pros and cons before making a decision about using allergy skin testing as one of the tools to make the best possible diagnosis for the patient. A good diagnosis allows for the best treatment plan to be developed.

Disclaimer: This article is intended for information purposes only. It is not a substitute for medical attention and supervision.

Sources:

Ehrlich, Paul M. Teen’s Guides: Living with Allergies. New York: Checkmark Books, 2009.

Barber, Marianne S. The Parent’s Guide to Food Allergies: Clear and Complete Advice from the Experts on Raising Your Food-allergic Child. New York: Henry Holt and Company, 2001.

Hospital for Sick Children: The Complete Kid’s Allergy and Asthma Guide: The Parent’s Handbook for Children of All Ages. Ed. Dr. Milton Gold. Toronto, Canada: Robert Rose Inc., 2003.

Website: American Academy of Allergy, Asthma and Immunology, updated March, 2005. Visited August 30, 2009.

Website: American College of Allergy, Asthma and Immunology, updated March, 2005. Visited August 30, 2009.

For other articles about diagnosing allergies see Allergy Blood Tests Help to Diagnose Allergies, Diagnosing and Treating a Drug Allergy and Basic Information About Eczema.