The Different Types Of Allergy Testing For Asthma

When your medical history, physical exam, and lab tests point to allergies as the major reason in your asthma, skin testing is usually done. There are different types of skin test: the prick or puncture test, the scratch test, and the intradermal test. In the prick test, the test allergen is placed on top of the skin, and the skin is pricked through the drop. In the scratch test, the skin in lightly scratched and a drop of the test allergen is placed onto the scratched area. In the intradermal test, allergen is injected beneath the skin with a very small needle. The weaker scratch or prick tests are usually done first to minimize the chances of triggering an allergic reaction. If these tests are negative, a stronger intradermal test is administered.

If you are allergic to any of the test allergens a wheal-and-flare reaction will develop at the test site. The flare is the redness. The wheal is the white center in the middle of the redness. In practice an urticaria or hive is produced, and the size of the urticaria can be anything from 2mm onwards. The higher the size of the hive means higher sensitivity to the testing substance.

Skin tests are most helpful in identifying an allergy to inhaled substances such as house dust mites, molds, pollens, or animal saliva or dander. It will clearly show which type of allergens are playing a role in your asthma. Though skin test methodology has not changed since decades these are very valuable and accurate ways to determine the presence of allergies. They are inexpensive and are very safe when carried out under the supervision of a physician who is knowledgeable in allergy skin testing. Skin test results are available within an hour after the tests are applied.

It is also possible to detect allergies with blood tests. In these tests a small sample of blood is processed through an analyzer to see if the blood contains allergic IgE antibodies to certain allergens. These tests are very helpful when the doctor cannot perform skin tests because of a skin eruption or a patient's fear of needles or when there is a chance of inducing an allergic reaction with skin tests. However allergy blood tests are not considered as accurate as skin tests. Finally it all depends on the doctor and the allergy specialist to interpret the results and correlate with patient's medical history to arrive at the exact allergens that trigger asthma.