I would like to discuss how an allergist evaluates someone to see if they have seasonal allergies since the spring time is approaching. First of all, the allergist will ask you questions about your symptoms.
The typical seasonal allergy symptoms include runny or stuff nose, itchy and/or red eyes, sneezing, hives and sometimes some coughing or wheezing. Some patients may also experience sinus infections as well. Sinus infections are the result of your nose being congested and inflamed which makes it more difficult for bacteria to be cleared. The spring allergy season is starting and people who are allergic to trees and grasses will soon begin experiencing these symptoms.
There are two ways in which an allergist can test a patient to see if they have an allergy to something--by a skin test or by a blood test. Both tests are good at determining whether a person has an allergy to (or in other words, a hypersensitivity to) a particular item (eg grasses, trees, molds, etc). The skin prick testing may sometimes give “false positive” results, however, meaning that you may not actually have an allergy to that item. The advantage of the skin prick testing is that it is fast and you can find out in about 10-15 minutes to what you are allergic.
In order to do the skin prick test, you must not be taking an anti-histamines (such as benadryl, Claritin, Allegra, Zyrtec, or even some nasal sprays such as Astelin) for about 5 days. These medications will interfere with the test. If you have asthma and are taking inhaled or oral steroids, these medications are fine to continue and will not interfere with the test. When making an appointment with the allergist, ask ahead if you should discontinue any of your medications.
To perform the test, the allergist will usually do it on the inside part of your forearm, however, sometimes the back is used. He or she will then take extracts, which are basically the protein contents of the specific item such as grass, tree, cat, etc. and place a small drop on your skin. Then, he or she will take a plastic prick and prick the area on the skin where the drop is to let it penetrate. Besides placing drops of the different items that are being tested, the allergist will place “control” drops. These control drops will be 1) a drop of histamine which should give a reaction and 2) a drop of saline (salt water) which should not give a reaction.
The histamine drop reaction allows the allergist to make sure that the test is working and gives us an idea of what a positive response should be. The saline drop is important because some people’s skin is very sensitive and reacts to everything. If this happens, then we know that the skin test results will not be accurate. The response on the skin will look like a mosquito bite, with a raised area in the middle and a red area surrounding it.