Overview of an Allergy Blood Test
Allergy Test Blood
Through an allergy blood test, physicians are able to measure the amount of allergen-specific antibodies in the blood. This type of testing screens for at least ten of the most common allergy triggers, which include, trees, grasses, weeds, molds, pet dander, dust, and food-related allergies. An allergy blood test is best suited for you if you: are taking a medicine that can interfere with results, cannot tolerate the needle scratches from a skin test, have an unstable heart condition, have a severe skin condition, might have an extreme reaction to an allergen during skin testing or have poorly controlled asthma.
What to Expect of an Allergy Blood Test
An allergy blood test is not complicated. To begin, your allergist will begin by cleaning the spot with alcohol. The allergist will then draw your blood with a needle, and put a bandage on the site of the injection. The results should be back within a few days. For children going through the allergy blood test, it is recommended that the child sit on the parent’s lap or distract them with a toy. The blood test is looking for the presence of IgE antibodies in your system. Skin tests are done more frequently, as a blood test can be less sensitive. Once the test results come back, your allergist will be able to discuss with you about what allergens you are sensitive to and also make an allergy action plan. An allergy action plan will help you plan out ahead of time what you should do in case of an allergic reaction. It is also best to give these plans to people that you are around frequently so they know how to help.
Types of Allergy Blood Tests
There are two types of allergy blood tests which are enzyme-linked immunosorbent assay (ELISA or EIA) or radioallergosorbent test (RAST). In some cases an allergy blood test may also be referred to as immunoassay tests. Both of these tests are used to measure the amount of allergen-specific antibodies in the blood. The ELISA test is the most common test. Allergies can also cause an increase in certain types of white blood cells, so your allergist may also recommend having a white blood cell count done. This test is called eosinophil. There are usually no dangers in having a blood test done to check for allergies, however, you may notice swelling or redness at the site of the needle, pain, or bleeding at the needle site. Some people may faint during blood testing of any kind.
Advantages of Allergy Blood Tests
In most cases, an allergy skin test is the most preferred method of allergy testing. However, there are a few reasons that the skin test cannot be done. For example, if you have a serious, life-threatening allergy, it is not safe to put you in contact with the allergen. There are a variety of medications that may also interfere with test results, such as steroids, antidepressants, or antihistamines. Some people may not also be able to handle the multiple needle scratches that are required for skin testing. Other conditions such as asthma, heart conditions, or severe skin conditions may also require blood testing. A blood test can also show your allergist if you have outgrown your allergy or if immunotherapy is working.
A blood test can be done at any time, regardless of the medication that you are currently on. It is also more appealing to people that are afraid of needles, as there is only one needle involved instead of multiple in the skin test. It is also easier to complete in young children.
Why Choose an Allergy Blood Test?
A blood test may be a better option for people who are not able to stop taking their medications. In some cases, medications will interfere with the accuracy of a skin test; therefore, a blood test is the better option. In people with severe skin disorders or if your skin reacts to almost anything, it is very difficult to read a skin test, so a blood test is much easier to read.
Allergy Blood Test Results
If there is a positive result in your blood test, that usually is a sign of the allergen. The blood test shows exactly what the allergy is to. You can also test positive to an allergen even if you have never had an allergic reaction to it before. If the result comes back negative, it shows there is no true allergy. Sometimes this is not completely accurate, as you may still have an allergic reaction to something that you tested negative for. Your allergist will be able to read the blood test and take into consideration the symptoms you are experiencing as well as the medical history to come to a proper diagnosis.
“False Positive” Results
About 50-60% of allergy blood tests will show a false positive result. A false positive means that the blood test shows a positive reaction even though you are not actually allergic. This may occur because it is measuring the undigested food proteins. The test may also detect certain proteins that are similar among different foods.
Summary of an Allergy Blood Test
An allergy blood test works well for people that are not able to have a skin test done. The skin test is typically the preferred test of allergists as it is less expensive and has a higher change of being accurate. Some conditions that will decide if a blood test is better is severe skin reactions or medications that you are on. The blood test will show your allergist what substances that you are allergic to and from there you both can create an allergy action plan. A blood test is done through a simple blood draw and results are back to you within a few days. In some cases, a “false positive” occurs which can be a result of an undigested food protein or the test detecting a similar protein. The physician will take the test results, your symptoms, and medical history into account before diagnosing an allergy.