Tips to Remember: What is allergy testing?

If you are allergic, you are reacting to a particular substance. Any substance that can trigger an allergic reaction is called an allergen. To determine which specific substances are triggering your allergies, your allergist/immunologist will safely and effectively test your skin, or sometimes your blood, using tiny amounts of commonly troublesome allergens.

Allergy tests are designed to gather the most specific information possible so your doctor can determine what you are allergic to and provide the best treatment.

Who should be tested for allergies?
Adults and children of any age who have symptoms that suggest they have an allergic disease. Allergy symptoms can include:

• Respiratory symptoms: itchy eyes, nose, or throat; nasal congestion, runny nose, watery eyes, chest congestion or wheezing
• Skin symptoms: hives, generalized itchiness or atopic dermatitis
• Other symptoms: anaphylaxis (severe life-threatening allergic reactions), abdominal symptoms (cramping, diarrhea) consistently following particular foods, stinging insect reactions other than large local swelling at the sting site.

Generally, inhaled allergens such as dust mites, tree, grass or weed pollens will produce respiratory symptoms and ingested (food) allergies will produce skin and/or gastrointestinal symptoms or anaphylaxis but both types of allergens (ingested and inhaled) can produce the spectrum of allergy symptoms.

What are the reasons for undergoing allergy skin testing?
To help you manage your allergy symptoms most effectively, your allergist/immunologist must first determine what is causing your allergy. For instance, you don't have to get rid of your cat if you are allergic to dust mites but not cats.

Allergy tests provide concrete specific information about what you are and are not allergic to. Once you have identified the specific allergen(s) causing your symptoms, you and your physician can develop a treatment plan aimed at controlling or eliminating your allergy symptoms. With your allergy symptoms under control you should see a considerable improvement in the quality of your life. Improved sleep quality because of less congestion, days without constant sneezing and blowing your nose, improved ability to exercise, and better control of your atopic dermatitis (eczema) are some of improvements you may gain from your allergy treatment plans.

Which allergens will I be tested for?
Because your physician has made a diagnosis of allergies, you know that one or more allergens is causing your allergic reaction—itching, swelling, sneezing, wheezing, and other symptoms. Your symptoms are probably caused by one of these common allergens:

• products from dust mites (tiny bugs you can't see) that live in your home;
• proteins from furry pets, which are found in their skin secretions (dander), saliva and urine (it's actually not their hair);
• molds in your home or in the air outside;
• tree, grass and weed pollen; and/or
• cockroach droppings.

More serious allergic reactions can be caused by:

• venoms from the stings of bees, wasps, yellow jackets, fire ants and other stinging insects;
• foods;
• natural rubber latex, such as gloves or balloons; or
• drugs, such as penicillin.

All of these allergens are typically made up of proteins. Allergy tests find which of these proteins you may be reacting to.

The allergen extracts or vaccines used in allergy tests are made commercially and are standardized according to U.S. Food and Drug Administration (FDA) requirements. Your allergist/immunologist is able to safely test you for allergies to substances listed above using these allergen extracts.

Prick Technique: The prick technique involves introducing a small amount of allergen into the skin by making a small puncture through a drop of the allergen extract. If you have an allergy, the specific allergens that you are allergic to will cause a chain reaction to begin in your body.

People with allergies have an allergic antibody called IgE (immunoglobulin E) in their body. This chemical, which is only found in people with allergies, activates special cells called mast cells. These mast cells release chemicals called mediators, such as histamine, the chemical that causes redness and swelling. With testing, this swelling occurs only in the spots where the tiny amount of allergen to which you are allergic has been introduced. So, if you are allergic to ragweed pollen but not to cats, the spot where the ragweed allergen touched your skin will swell and itch a bit, forming a small dime-sized hive. The spot where the cat allergen scratched your skin will remain normal. This reaction happens quickly within your body.

Test results are available within 15 minutes of testing, so you don't have to wait long to find out what is triggering your allergies. And you won't have any other symptoms besides the slightly swollen, small hives where the test was done; this goes away within 30 minutes.

Intradermal: involves injecting a small amount of allergen under the skin with a syringe. This form of testing is more sensitive than the prick skin test method. This form of allergy testing may be used if the prick skin tests are negative.

Other Allergy Testing Techniques

Scratch tests: The term scratch test refers to a technique not commonly used at the present, which involves abrading the skin and then dropping the allergen on the abraded site.

Challenge testing: Involves introducing small amounts of the suspected allergen by oral, inhaled or other routes. With the exception of food and medication, challenges are rarely performed. When they are performed, the must be closely supervised by an allergist/immunologist.

Blood (RAST) test: Sometimes your allergist/immunologist will do a blood test, called a RAST (radioallergosorbent) test. Since this test involves drawing blood, it costs more, and the results are not available as rapidly as skin tests. RAST tests are generally used only in cases in which skin tests can not be performed, such as on patients taking certain medications, or those with skin conditions that may interfere with skin testing.

Other types of allergy testing methods the American Academy of Allergy, Asthma and Immunology considers to be unacceptable are: applied kinesiology (allergy testing through muscle relaxation), cytotoxicity testing, urine autoinjection, skin titration (Rinkel method), provocative and neutralization (subcutaneous) testing or sublingual provocation. If your physician plans to conduct any of these tests on you, please see an AAAAI member allergist/immunologist for appropriate allergy testing.

Who can be tested for allergies?
Adults and children of any age can be tested for allergies. Because different allergens bother different people, your allergist will take your medical history to determine which test is the best for you. Some medications can interfere with skin testing. Antihistamines, in particular, can inhibit some of the skin test reactions. Use of antihistamines should be stopped one to several days prior to skin testing.

When to see an allergy/asthma specialist
Allergy testing by an allergist/immunologist may be helpful in patients with anaphylaxis (systemic allergic reaction), asthma, allergic pneumonia, conjunctivitis, cough, dermatitis, drug allergy, food allergy, insect allergy, rhinitis, sinusitis, urticaria and angioedema.

Your allergist/immunologist can provide you with more information on allergy testing.

Tips to Remember are created by the Immunotherapy Committee of the American Academy of Allergy, Asthma and Immunology.

The content of this article is for informational purposes only. It is not intended to replace evaluation by a physician. If you have questions or medical concerns, please contact your allergist/immunologist.

 ©2006, American Academy of Allergy, Asthma and Immunology. All rights reserved. This article has been reproduced with permission of AAAAI as a member.