Get to Know Your Allergy Triggers

Knowing what you are allergic to is the first step in avoiding uncomfortable allergic reactions. While you can learn a lot by trial and error, getting tested by your doctor or allergist will give you a definitive answer, allowing you to receive proper treatment for your allergies.

What is Allergy Testing?
Doctors have been using skin tests to diagnose allergies for more than a century. These tests, which are safe for people of all ages, expose you to a minute amount of allergen, then measure how sensitive you are to the substance.

About ten days before you have a skin test, you will need to stop taking any medications that could interfere with your results. These medications include both over-the-counter and prescription antihistamines (such as fexofenadine and cetirizine), tricyclic antidepressants (amitripyline and doxepin, for example) and heartburn medications (like cimetidine and ranitidine).

Here's a rundown of the three main types of skin tests for allergies:
  • Scratch test. This is the most common type of allergy testing. Tiny amounts of purified allergen samples are pricked or scratched into the surface of your skin. This test is usually used to identify dozens of allergies, such as pollen, mold, animal dander, dust mites, foods, insect venom and penicillin.
  • Intradermal test. For this test, purified allergens are injected into the skin of your arm. This is a common test when looking for insect venom or penicillin allergies.
  • Patch test. Your doctor will apply an allergen to a patch, and then place the patch on your skin and check for a reaction. This is usually done to identify substances that cause skin irritation (known as contact dermatitis), latex, medications, fragrance, metal, hair dye, resins and preservatives. The patch may remain in place for several days in order to get the most accurate testing possible.

What to Expect
Skin prick or intradermal tests cause little, if any, pain or discomfort because the needle barely penetrates the skin's surface. With these tests, you'll see an immediate reaction if you are allergic to a particular substance, while reactions to patch tests may take several days to appear. If you're allergic to a substance, a red, itchy bump will develop, much like a mosquito bite. Larger bumps represent a higher rate of sensitivity, while a negative result (no bump) means you probably aren’t allergic to that substance.

The most common side effect of any skin test is redness and itchiness at the site. This usually subsides after a few hours. In rare cases, skin tests can result in a severe allergic reaction. If this occurs, your doctor will have the appropriate medications on hand to treat the reaction. If a severe reaction develops after you leave the office, call your doctor immediately or dial 911 in extreme circumstances.

Remember that allergies can develop and change throughout your life. While you may test negative for a particular substance now, you could develop an allergy to it later. You may want to undergo additional testing in the future, if you find you have new reactions to once benign substances.

These skin tests can confirm what you may already suspect—that your sneezing, itchy and watery eyes, or hives are the result of an allergy. Your doctor can then use this information to create a personalized treatment plan that may include allergen avoidance, medications to reduce your symptoms, or immunotherapy (allergy shots) to gradually increase your tolerance to allergens.