Allergy testing is often necessary to determine the exact triggers of a patient’s allergic response. Patient testing is an instrumental tool in diagnosing a patient’s allergy triggers. The tests are also used to develop an effective treatment regimen. Skin tests are the most common way to determine the culprit. These tests are typically more reliable and less expensive than blood tests. However, either method is considered effective by physicians.
What Allergies Can Allergy Testing Detect?
Patients may have a variety of allergies from hay fever to bee venom. Other allergic responses include allergic asthma, asthma of the skin or eczema, food allergies, penicillin allergy and latex allergy. Allergy testing will also test patients for pollen, dust mites and pet dander. Food allergies are the most complex to determine and may require several tests to reach a valid diagnosis.
What Can I Expect From Allergy Testing?
When an allergy test is administered, a small amount of the allergen is placed on or below the skin to determine if a rash develops. There are three different types of tests that employ this technique:
Skin Prick Test. This test places the allergen on the patient’s skin and then uses a needle to prick the skin to allow the possible allergen to penetrate the surface. If a red, raised itchy patch develops, called a wheal , then the person has a positive reaction and is deemed allergic to the allergen.
Intradermal Test. This is the second phase of testing for a patient. When the physician suspects that a person may be allergic to a substance, but it does not cause a reaction in a skin prick test, an intradermal test may be used for allergy testing. This test uses a needle to inject the allergen solution directly into the skin. People may not exhibit symptoms to an allergen, but they may still be allergic to a substance. This test will help physicians determine the cause definitively.
Skin Patch Test. With this test, the potential allergen solution is placed on a swab or pad. The physician tapes this pad to the skin for 24 to 72 hours to determine if the person is allergic to the allergen through contact alone. The physician often refers to this as contact dermatitis.
Skin testing is an effective method of testing for infants to adults. Some physicians may advise against skin testing if the following conditions are present:
Patients Who Have Had a Severe Allergic Reaction. If the patient has had a life threatening reaction, such as anaphylaxis, then a skin test should not be performed.
Patients Taking Medications that May Skew Results. Antihistamines, antidepressants, asthma medication and heartburn medications may interfere with skin tests. Specific medications may include Allegra, Claritin, Alavert, Benadryl, Zyrtec, NyQuil, Alka-Seltzer Plus, amitriptyline, doxepin, Tagamet, Zantac and Xolair. Some physicians may decide that patients should continue taking their medications rather than discontinue them for the test.
Patients with a Widespread Skin Reaction. Patients with severe eczema or psoriasis on most of the body, specifically the arms and the back, will not have enough clear skin to perform the test and accurately analyze the results.
Other Skin Conditions Present. Conditions such as custaneous mastocytosis, dermographism and urticaria may cause unreliable test results.
Risks Associated Allergy Testing
Most patients will experience swollen, red or itchy bumps or wheals. During the test, the wheals may become more noticeable. However, the bumps should subside in a couple of hours or even in a day or two. A cortisone cream may alleviate the symptoms of itching and redness. If a severe allergic reaction develops in the days after a skin test, a physician should be contacted immediately.
How to Prepare for Skin Tests
The physician will typically ask the patient detailed questions about their medical history, signs and symptoms. Current treatment plans will also be discussed. The physician will help you determine if your allergies are hereditary or if an allergic reaction is causing your symptoms. A physical examination may also be performed to provide additional information about the issues.
Blood tests are recommended for those that cannot participate in skin tests. Blood tests, however, are more expensive. The physician will recommend the most appropriate test for the patient.
Blood Test
Allergy blood tests do not detect the allergens as well as the other skin tests available. However, some people simply cannot have skin tests for a number of reasons. One reason may be that there is not clear location on the body to be able to produce an accurate reading. A physician will determine when the patient will require a blood test.
There are several types of blood tests:
Enzyme-Linked Immunosorbent Assay (ELISA).This blood test will measure the blood levels for the antibody, Immunoglobulin E (IgE). People that have allergies or asthma will have higher levels IgE.
Radioallergosorbent Testing (RAST). An immunoassay capture test may also be used to provide more detailed information of the type of allergen triggering an allergic response.
Consult with a physician to determine the appropriate allergy testing mechanism that is right for you. The physician can provide detailed information about whether a skin test, blood test or both will be required.
