Allergy skin tests

During allergy skin tests, the skin is exposed to suspected allergy-causing substances, called allergens, and then checked for signs of an allergic reaction. Along with a medical history, allergy tests may be able to confirm whether a particular substance a person touches, breathes or eats is causing symptoms.

Information from allergy tests may help a healthcare professional develop an allergy treatment plan that includes allergen avoidance, medicines or allergy shots, called immunotherapy. Allergy skin tests are widely used to help diagnose allergic conditions, including: Hay fever, also called allergic rhinitis. Allergic asthma. Dermatitis, called eczema. Food allergies. Penicillin allergy. Bee venom allergy. Skin tests are generally safe for adults and children of all ages, including infants. In certain circumstances, though, skin tests aren't recommended. A healthcare professional may advise against skin testing if you: Have ever had a severe allergic reaction. You may be so sensitive to certain substances that even the tiny amounts used in skin tests could trigger a life-threatening reaction, known as anaphylaxis. Take medicines that could interfere with test results. These include antihistamines, many antidepressants and some heartburn medicines. Your care professional may determine that it's better for you to continue taking these medicines than to temporarily discontinue them in preparation for a skin test. Have certain skin conditions. If severe eczema or psoriasis affects large areas of skin on your arms and back — the usual testing sites — there may not be enough clear, uninvolved skin to do an effective test. Other skin conditions, such as dermatographism, can cause unreliable test results. Blood tests known as in vitro immunoglobulin E antibody tests can be useful for those who shouldn't or can't undergo skin tests. Blood tests aren't used for penicillin allergy. In general, allergy skin tests are reliable for diagnosing allergies to airborne substances, such as pollen, pet dander and dust mites. Skin testing may help diagnose food allergies. But because food allergies can be complex, you may need additional tests or procedures.

The most common side effect of skin testing is slightly swollen, red, itchy bumps, called wheals. These wheals may be most noticeable during the test. In some people, though, an area of swelling, redness and itching may develop a few hours after the test and remain for a couple of days. Rarely, allergy skin tests can produce a severe, immediate allergic reaction. For this reason, it's important to have skin tests performed at an office where appropriate emergency equipment and medicines are available.

Before recommending a skin test, you will be asked detailed questions about your medical history, your symptoms and your usual way of treating them. Your answers can help determine if allergies run in your family and if an allergic reaction is most likely causing your symptoms. Your healthcare professional also may do a physical examination to search for more clues about the cause of your symptoms.

Skin testing is usually done at a medical professional's office. Typically, this test takes about 20 to 40 minutes. Some tests find immediate allergic reactions, which develop within minutes of exposure to an allergen. Other tests find delayed allergic reactions, which develop over a period of several days.