asthma test | What Is The Test For Asthma

asthma test

 ASTHMA AND THE PROOF OF ALLERGIES IN THE SKIN
Many asthmatics are allergic to substances that breathe on a daily basis. These tiny particles that can cause allergic reactions are called "allergens." Some examples of allergens in the air are: pollen from grass, trees and herbs; the spores of mold; the hair dandruff of cats, dogs and other animals; the debris of cockroaches and insects (mites) that live in the dust of the house. People with a tendency to allergies are usually only allergic to one of the allergens and not all. Also different people are allergic to different allergens.

When breathing allergens, asthma can get worse and cause asthmatic attacks
Daily breathing of the allergens to which you are sensitive may worsen the inflammation of the bronchial tubes in asthma (see the booklet, What inflammation means in asthma), may cause more activity in asthma (which means it is most likely to suffer from coughing, wheezing, shortness of breath, narrowing of the chest or waking up at night with asthma symptoms) and increasing the likelihood of having a severe asthma attack.

High exposure to an allergen to which you are sensitive can also cause a sudden attack of asthma or an attack that will develop a few hours after exposure.

Determining which allergens you are sensitive to can be very useful
You and your doctor can decide if it would be helpful to know which allergens affect you. At the Asthma Center we do not use this information to decide whether to start "allergy shots," (also called de-sensitizing injections), but to help reduce your exposure to those things that can make your asthma worse. For example, if you are very allergic to insects that live in the dust of the house, you could take simple actions that would decrease the amount of allergens in the dust you breathe, probably causing an improvement in your asthma.

Review your experiences with allergic exposures
To determine specifically to which allergens you are sensitive you begin by noting the exposures that have caused you asthmatic reactions in the past. For example: Does your asthma get worse in the spring or fall? Does it happen when you dust or vacuum? Does it happen when the room is humid? These examples and other similar questions are important in determining asthma allergies and interpreting the results of allergy tests.

Tests for allergic sensitivity
In addition to reviewing your previous experiences, there are two basic methods of testing your sensitivity to various allergens. The first involves a blood test to analyze the antibody proteins your body may have made when reacting to a particular allergen; The second is to test the skin to see the reactions to the allergens that you can inspire. At the Asthma Center we rely primarily on skin tests because they are more sensitive, less expensive, give immediate results and can test a larger and more varied number of allergens than in the blood test. This brochure discusses this process in detail.

How are allergy tests done on the skin?
To test your reaction to an allergen, a drop of the allergen liquid is placed on the skin (usually inside the forearm). The drop is placed on the first layer of the skin, in an area where a puncture will be given. This type of skin test is called a "prick test." If you are allergic to the allergen, the skin will begin to react after about 5 minutes. It can redden and inflame. The area will itch and a welt will form. The welt will be measured and the measurement recorded. The larger the wheal, the more likely you are to be allergic to the allergen that was used.

The different types of allergy skin tests
Sometimes, if a very intense allergic reaction is suspected, only a light scratch will be made under the liquid containing the allergen ("scratch test"). In this way only a minimal amount of the allergen is introduced into the skin. At other times, when it is particularly important to investigate sensitivity to a specific allergen, a small amount of the fluid is injected under the surface of the skin with a thin needle ("intra-dermal test"). This method puts a greater amount of the allergen on the skin.

The common practice of allergy skin tests is to test a group of allergens to which the person has sensitivity. At the Asthma Center we usually test 25 to 30 allergens. The 25-30 drops of liquid allergens are placed in a row on each forearm and then a puncture is made under each one. The results of the test take 15 minutes.

What are the chances of having reactions to allergy tests?Adverse reactions from skin allergy tests are rare, but they can occur. It is possible that the small amount of the allergen in the skin can cause an asthma attack and, what is even more rare, a dangerous period of low blood pressure, called an anaphylactic reaction. Because the tests carry these risks, although minimal, you will be asked to sign a consent. To ensure that late reactions do not occur, you will be asked to remain under our medical observation for one or two hours after the test.

The interpretation of the results of the skin allergy test
Your doctor will interpret the results of allergy skin tests. These tests are based on the reactions you will have on the skin due to the allergen. A reaction is a "positive" result. You would probably have an allergic reaction in the bronchial tubes of the lungs if you breathed in the allergen that caused the reaction in the skin. Although this is not always the case, it often is, especially if you have had asthmatic symptoms when exposed to the allergen.

If your skin does not react to the allergen the result is "negative" and if you have not had asthmatic symptoms when the allergen breathes, you are almost certainly not sensitive to that allergen.

The medicines you should avoid before the allergy test
Finally, if you have taken certain medications before the allergy skin test you may get a resultwrong. These medications are called antihistamines. The most common examples of antihistamines are:Chlortrimeton®, Claritin®, Clarinex®, Zyrtec® and Allegra®. Any of these medications can affect the results ofthe test until several days after taking them. As a result, you will be asked to avoid all antihistaminesfor several hours or days before the test.