The human body is designed to protect itself from viral and bacterial attacks by triggering an immune response when a harmful antigen is discovered in the body. In a person with allergies, the body sees everyday substances, called allergens, as attacks and produces this immune response to protect itself. Common allergens include plant pollen, tree pollen, animal dander, dust, medicines, insect bites, food and mold.
When the body reacts to these normally harmless substances, the response it generates is called an allergic reaction. Common symptoms of allergic reaction include sneezing, runny eyes, runny nose, rashes or hives, itching, swelling and even asthma. These symptoms can range from mild to severe and can really have an impact on daily life. In the case of insect bites and some foods, anaphylactic shock caused by the allergy can be fatal.
When allergy symptoms are prolonged and having a negative impact on life, it is time to consider allergy testing. Testing for allergies involves exposing the body to known allergens in an attempt to recreate the immune response. This will narrow down specific allergens in order to begin a treatment plan, which usually just involves avoiding the allergens that are causing the reaction. Certain medications known as antihistamines are sometimes prescribed to help with symptoms. In the case of bee stings or other insect bites, an emergency dose of epinephrine is critical in thwarting a severe reaction.
The importance of allergy testing is to rule out possible allergens, especially when multiple allergens are present in daily life. It makes no sense to begin avoiding one potential allergen when the reaction is actually caused by something entirely different.
Types of Tests for Allergies
Skin Testing
The most common form of skin allergy testing is the skin prick test. This method is relatively painless and involves placing a small amount of allergen on the skin and pricking or scraping the surface of the skin to get the substance into the skin. Multiple allergens are placed at the same time in different sections. Within 15 minutes or so, the areas where the true allergens are placed will begin to react with a slight rash. In areas where the allergen is not the one a person is allergic to, no response will be seen. Since results for this test are available within minutes, it is the fastest way to isolate specific allergies.
If the skin prick test does not show expected results, such as when a cat allergy is expected but there is no reaction to cat allergens, an intradermal test may be ordered. In the intradermal test, a small amount of the allergen is injected into the skin. While more sensitive than the skin prick test, the intradermal test can sometimes lead to false positives.
The third skin test is used to test for contact dermatitis. A pad soaked with the allergen solution is applied to the skin and kept there for 1-3 days. Since this test is for a very specific allergic reaction, it finds less use than skin prick or intradermal testing.
Blood Testing
Blood allergy testing is not as sensitive as skin testing and is generally reserved for people who cannot have allergy tests, such as those with skin conditions or who are on medications that inhibit the effectiveness of a skin test. The prohibitive cost and lengthy wait for results of these tests also tend to be a factor in favoring the skin tests over blood testing. Results are usually available in about seven days.
The enzyme linked immunosorbent assay, or ELISA, is the most commonly used blood test to check for allergies. In this test, an allergen is bound to antibodies and a developer is added that will change the color to test for reaction. The darker the color changes, the larger the concentration of antibodies in the blood.
One area where blood testing outshines skin testing is in food allergy testing. Blood tests are better able to show immune reactions to certain foods than the traditional skin tests.
Is Allergy Testing Safe?
Skin testing is very safe, even for young children and infants. The reaction is generally isolated to the specific area the allergen is applied to, and it quickly dissipates. People on certain medications like beta-blockers or antihistamines should not be given a skin test, nor should people with very sensitive skin who have a bad reaction to the control test.
In blood testing, blood is drawn from the patient and then tested. There is no chance of reaction because the allergen never comes in contact with the patient.
Living with an allergy can be a miserable experience. Sufferers can experience a dramatically lower quality of life when in the throes of an allergic reaction. This is especially true during allergy season when common allergens abound in the air. Allergy testing can bring about a return to normal living by isolating the specific allergies and giving a patient the chance to treat and recover from allergies.