Allergy Testing

If you are having allergy skin testing, your skin will be exposed to allergens in order to see if your skin shows signs of local allergic reaction.  Allergy tests have the ability to confirm whether or not the signs and symptoms you are experiencing are due to allergens.  Allergy tests can also determine the exact substances that trigger the allergic reactions.  The information from the allergy tests can assist the doctor with determining an allergy treatment plan that is best for you.  This may include medications, allergy shots, and allergen avoidance. 

Often, allergy skin testing is performed in order to diagnose allergic conditions like allergic asthma, hay fever, food allergies, eczema, bee sting allergy, and penicillin allergy.  Skin testing can be performed for people of any age, from babies to the elderly.  In some cases, skin testing may not be recommended due to a suspected allergy being so severe that even a small amount of the substance could cause you to have a severe allergic reaction, if you have a severe skin disease which will not allow there to be enough unaffected skin to provide a clear result, or if you take medications that may cause an inaccurate test result.  This may include antidepressants, antihistamines, and heartburn medications.

When you have your skin tested, you may have some slightly swollen, itchy, and red bumps, known as hives.  These hives will most likely go away after a few hours, but they may be present for a day or two.  You may wish to use a mild cortisone cream in order to relieve the redness and the itching.  In some cases, the skin tests can result in immediate severe reactions, so it is important that there are emergency personnel nearby when allergy tests are performed.  If you experience a severe allergic reaction soon after the skin test, you need to see your doctor right away. 

Before your doctor determines if a skin test is right for you, he or she will ask many questions about your health history as well as any signs and symptoms you have experienced.  A physical examination and your medical history may be enough for your physician to begin discussing your treatment.  In this case, a skin test may be unnecessary.  However, if your doctor is uncertain or wants clarification, a skin test may be ordered. 

Additionally, before your skin testing occurs, your doctor will need to know all of the over the counter medications and prescription drugs you are currently taking, as some can suppress allergic reactions and prevent the skin test from being valid.  Other medications may increase your risk of developing an allergic reaction.  Your doctor may even ask for you not to take certain medications for up to ten days prior to your appointment. 

Skin testing usually occurs in the doctor's office.  Normally a nurse will administer the test and then your doctor will need to interpret it.  The skin test should not be painful.  The needles that are used barely penetrate the surface of your skin, so you will not feel much more than discomfort that lasts only a moment. 

There are three different types of skin tests.  The first is puncture, prick, or scratch test.  This test includes tiny drops of the purified allergen being scratched or pricked into the surface of your skin.  This test is normally performed in order to identify the allergies to the mold, pollen, pet dander, foods, and dust mites.  In an intradermal test, the purified allergen extracts are injected into the skin of your arm.  This test will likely be administered if it is suspected that you are allergic to insect venom or penicillin.  A patch test is one that does not use needles.  The allergen is placed on a patch, which is then put on your skin.  The test is utilized in order to identify the substances that are the cause of contact dermatitis.  These causes may include fragrances, medications, hair dyes, preservative, metals, or resins. 

A prick, scratch, or puncture test is done in order to determine allergic reactions to up to forty different possible allergens at a time.  The test in adults is usually performed on the forearm, and in children it is usually tested on the upper back.  Once the area has been cleaned with alcohol, the nurse will draw small markings on your skin and then apply a small drop of allergen next to each marking.  Then a sharp lancet is used to introduce the extract into the surface of the skin.  A new lancet is used for each scratch so that there is no cross-contamination of any allergens.  The drops are placed on the skin for approximately fifteen minutes, and meanwhile the nurse will watch your skin for any signs of allergic reactions.  The nurse will also use two controls.  One is a histamine, which should cause a response.  A second control is saline or glycerin, which is a substance that should not cause any reaction.  If your skin reacts to the saline or the glycerin, you may have sensitive skin, and so your doctor may need to interpret the results of your allergy test with caution. 

Before leaving the doctor's office, you will learn the results of the skin allergy testing if you have had a prick, scratch, or puncture test.  However, a patch test may take a few days or longer in order to produce any results.  A positive skin test confirms that you are allergic to a substance.  Generally the larger the bumps, the more severe the allergy.  If there is a negative skin test, the result is that you are likely not allergic to that substance.  Generally, skin tests are reliable for diagnosing allergies to pet dander, dust mites, and pollen.  The diagnosis of food allergies may be more complex and may require more procedures or testing to be performed.  Some of the treatments for allergies may include dietary changes, medications, or immunotherapy (allergy shots).