Admin_NHT Staff asked 6 years ago A scratch test or an allergy skin test is done to test for any allergies that an individual may have. In the test, the individual’s skin on his arm is scratched and exposed to a range of allergy-causing substances. The reaction or lack of it is used to determine if the person is allergic to the particular substance or not. These tests are considered as an important part of your medical history and it is advised to get allergy tested at least once in your lifetime. This test is used to help the doctor diagnose allergic asthma, hay fever, eczema, and penicillin allergy, along with other airborne substances and food allergies.
Before an allergy test the person is advised to not take any antihistamines, asthma relieving drug, antidepressants, or medication for heartburn as these drugs interfere with the results. The whole test takes about 20-40 minutes where a nurse administers the test and the doctor interprets it. During the test, the skin is initially cleaned with alcohol and marked. Allergen extracts are applied on each mark. To set a baseline, two additional markings are done on the skin: one for histamine and the other for saline/glycerine. After about 15 minutes the nurse will check your forearm again to see for any signs of reactions. If you are allergic to a substance, an itchy, red bump (like a mosquito bite) will be visible on the site of the allergen. The bump’s size will be measured, and the results will be recorded.
Although you may test positive for certain allergens in the lab, it is very much likely that you may not have any kind of reaction to them in your everyday life. The severity of an allergic reaction is determined by the bump size on the forearm. There are also chances of you reacting to the same allergen differently under different environmental settings or at a different time in your life.