There are a few ways to test for peanut allergy. While the results of allergy testing are a guide to whether the person is allergic, they are not a reliable guide to whether the reaction will be mild or severe.
Blood test
A blood test (called a radioallergosorbent or RAST test) can measure your immune system's response to peanuts by measuring the immunoglobulin E (IgE) antibodies. A blood sample is sent to a medical laboratory, where it can be tested for evidence of sensitivity to peanuts.
Skin prick test
In this test, your skin is pricked and exposed to small amounts of the proteins found in peanuts to see if you have a skin response. If you're allergic, you develop a raised bump (hive) at the test location on your skin. Allergy specialists usually are best equipped to perform allergy skin tests. There is some early indication that the size of the skin response may be indicative of whether the allergy may be outgrown.
It is important to know that a 'positive' skin or blood allergy test means that the body's immune system has produced a response to a food; sometimes these are 'false positives'. In other words, the test may be positive yet the person can actually eat the food without a problem. For that reason, it is important to eventually confirm the significance of a positive allergy test (in some circumstances) with a deliberate supervised challenge.
Food Challenges
Although it can be an appropriate way to diagnosis food allergies, a food challenge should only be done under a health care doctor's supervision, Prior to initiating a food challenge, the peanut allergen must be eliminated from the diet. If symptoms remain unchanged and appropriate elimination diets have been utilized, a peanut allergy is not likely responsible for any symptoms that may be causing concern.
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