How to Diagnose Allergic Rhinitis
The presence of allergic rhinitis isn’t hard to determine — the clinical symptoms are pretty self-explanatory. However, knowing what the triggers of those symptoms are, which you can determine by various testing methods, may be important. Here are a few common tests that your care provider can administer:
Skin testing: For this test, your doctor places an extract of a common allergen on your skin and then scratches or pricks under the skin with a needle, exposing the skin mast cells to the allergen, and a wheal-and-flare reaction occurs.
The central area becomes infiltrated with cells and fluid, causing swelling, and the surrounding area becomes red from vasodilation. The size of the wheal roughly correlates with your sensitivity to the allergen.Credit: ©iStockphoto.com/John Phillip Young 2006
In vitro testing, such as RAST: RAST testing uses a blood sample to look for the amount of specific IgEs floating in the bloodstream. With this test, you’re able to look for multiple allergens with one blood sample.
Total IgE: Total IgE can be drawn as a blood test as well. The total IgE is higher in people who have allergic rhinitis, but this number doesn’t really tell you much. Your total IgE can’t tell you what you’re specifically sensitive to or how much of a problem it is, so the test isn’t very helpful.
Blood eosinophil count: Blood eosinophil count is a measurement routinely done during a CBC (complete blood count). It’s elevated in people who have allergic rhinitis, especially during the time of year they have the most symptoms, but again, it isn’t specific. Sometimes, it can help determine whether rhinitis symptoms are from allergies or something else (such as infectious causes), but otherwise, it isn’t of much value.
ELISA/act testing: ELISA/act testing looks for activated lymphocytes in the bloodstream. This testing looks for delayed sensitivity rather than just the immediate sensitivity markers found in RAST testing. Although it’s somewhat controversial and often not used in conventional medical offices, ELISA/act testing can be helpful in determining causes of immune response when they aren’t obvious.
Testing isn’t completely without incident. Rarely, people develop a severe reaction to skin testing. Some practitioners prefer introducing the allergen deeper into the dermis. Although this technique is more sensitive than prick testing, it should be done only by trained specialists.
It also can have high false positive and false negative results, meaning it can look like you’re sensitive when you’re not, or it can miss things you really are sensitive to. This is also an issue with RAST testing.