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How an Allergy Skin Prick Test Works |
 Allergists and immunologists are part of the medical profession that specializes in diagnosing and helping people deal with allergies. There are many ways to cope with allergies but sometimes allergy symptoms are so severe that the best course of action is to get tested for allergies so your allergist can prescribe the right solution for you. If that is the route your doctor recommends, you may be scheduled for a skin prick test. It helps to understand what lies ahead so this phase of allergy testing doesn’t take you by surprise.
A skin prick test involves placing a small amount of a suspected allergen under your skin to see if you demonstrate an allergic reaction to it. The allergen is placed under the skin with a small needle which is used to prick the skin to implant the allergen test. Before your skin prick test you will need to stop taking any antihistamine medication 48 hours prior to the test itself. Your doctor or nurse will determine which allergens to test for depending on your medical history.
The test is performed either on the back or the inside of the forearm. Each spot where an allergen will be put is marked with a letter or a number, so that the doctor will know which allergen went where. A small drop of each allergen is put on the skin, and then is pricked into the skin with a small sterile needle or lancet. This process is much less painful than a blood test and is virtually pain free to many people.
Every prick is done with a new needle or lancet to avoid any cross contamination. The excess drops are wiped off and the patient waits for fifteen minutes. It is important to note that there will always be two different kind of controls used for these tests. The negative control is salt water, which tests for a false positive reaction. Histamine is used as the positive control because everyone reacts to it.
After the allotted time, the nurse or doctor will come back in to go over the results of your test. If you have a positive reaction there will be a red, itchy bump at the site and the bump will be at least 2mm larger than the bump created by the salt water. If you have tested negatively, then there will be no response to a certain type of allergen and that allergen will be ruled out as one that is causing your allergic symptoms. It should be pointed out that certain skin conditions make it impossible to perform a skin test, such as widespread eczema.
Remember to stop taking any medication that has an antihistamine in it at least 48 hours before your test. Also, some antidepressants can cause problems with your test, so you may want to stop taking those 48 hours beforehand, as well. But make sure to discuss this with your doctor first and get his or her permission to temporarily go off of those medications. Other medications such as nasal sprays, inhalers, or steroids will not interfere with the results of the test so it might not be necessary to stop taking these before the test.
Skin prick tests are very safe. Since a new sterile lancet or needle is used for every prick there is no concern of bacteria getting in with the prick and no threat of cross contamination. Also, only a certified nurse or doctor can give the test. You can get them done at a regular clinic, though in most cases you will be referred to an allergy specialist for such a test.
A skin prick test is very reliable, if taken in consideration with medical history and if it is very carefully controlled. The false reactions are usually less than 1%. A skin prick test does not diagnose anything, though; it simply lets you know that you are allergic to a certain allergen. It is very helpful for narrowing down the allergens behind an allergic reaction.
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