Tests To Diagnose Allergies
For many years, doctors have used skin tests to diagnose allergies. During these tests, the skin is exposed to allergy causing substances, or allergens, and is then observed for signs of an allergic reaction. Combined with medical history, skin tests can confirm whether signs and symptoms such as sneezing, wheezing, and skin rashes are caused by allergies. These tests are also able to identify the specific substances that trigger allergic reactions. Such information will help the doctor develop an allergy treatment plan. This treatment plan may include allergen avoidance, medications, or allergy shots, also called immunotherapy.
Skin testing is widely used to diagnose allergic conditions such as allergic asthma, hay fever, and eczema. Skin testing is safe for people of all ages, including infants and older adults. Certain medications may interfere with skin testing, which may include antihistamines, antidepressants, and certain heartburn medications. Each doctor will determine if the medication should be discontinued in preparation for a test. If conditions such as eczema or psoriasis affect large areas of skin on the arms and back, the usual testing sites, there may not be enough clear skin to conduct an effective test.
Before recommending a skin test, a doctor will ask detailed questions concerning medical history, signs and symptoms, and the usual way they have been treated. Honest answers will help the doctor determine if allergies run in the family. A physical examination is helpful to search for additional clues about the cause of the symptoms. A through medical history and physical examination may provide enough information for the doctor and a skin test may not be necessary. If a doctor is uncertain allergies are the culprit of if the allergies require more information, he or she may recommend having a skin test performed.
Skin tests cause little if any discomfort. The needles used in these tests barely penetrate the surface of the skin so there is no bleeding. Some tests detect immediate allergic reactions, which develop within minutes of exposure to an allergen. Other tests detect allergic reactions, which develop over a period of several days. A puncture, prick, or scratch test checks for immediate allergic reactions to as many as forty different substances at one time. If a puncture, prick, or scratch test is inconclusive, a more sensitive immediate reaction test may me required. These tests are known as an intra-dermal test. During this test a thin needle injects a small amount of allergen extract just below the surface of the skin on the arm. The injection site is inspected after fifteen minutes for a local skin reaction.
If an allergen provokes an allergic reaction to a puncture or intra-dermal skin test, a red, raised, and itchy bump that may look like a mosquito bite, will develop. A positive skin test may mean that allergies to a particular substance exist. Bigger bumps usually indicate a higher degree of sensitivity. A negative skin test means that an allergy to a particular allergen does not exist. The accuracy of skin tests can vary. It is possible to react differently to the same test performed at different times. It is also possible to react positively to a substance during a test, but not react to it in everyday life.
