A drug allergy is an immune response to the medication which caused the allergy cells to release large amounts of histamine, causing hives, wheezing and a severe drop in blood pressure, or in extreme cases even death. For this reason, many physicians need to know if it was an allergy before reintroducing a lifesaving medicine. Some drug allergies are lifelong whereas some are temporary. For instance, 50% of people who are allergic to penicillin will lose the sensitivity within 5 years, 80% within 10 years.
Testing for drug allergy falls into three categories: skin testing, patch testing and graded oral challenges.
Skin Testing
Skin testing is performed when there are injectable forms of the drug and the breakdown components of the medicines are known. The drug penicillin after consumed, is broken down in the body into components called the major and minor determinants. When testing is performed, both the drug and determinants are tested, boosting the accuracy of the test to greater than 95%. This accuracy is important, as studies have shown that doctors are forced to use more potent and expensive medicines with a high rate of side effects to treat patient who would have otherwise done well on penicillin.
Patch Testing
Allergy patch testing is done with certain other medicines the components of which are not known. The advantage to this test is that it is simple to apply. The disadvantage is a positive test suggests that there is an increased risk to the medicine but a negative test doesn’t rule out that they are allergic.
Graded Oral Challenge
The definitive test to detect an allergy to a medicine is the graded oral challenge. In this test, tiny amounts of the medicine are given to the person who is kept under observation in the doctor’s office. The amount of medicine is gradually increased until a therapeutic dose is reached. If the person experiences any symptoms (which are usually mild) the challenge is stopped and the symptoms treated. This test is usually performed only if there is no skin testing available and the reaction to the drug was a questionable allergic reaction. This type of test is often performed for such medicines as aspirin where hives appeared.
Not all medicines can be evaluated by an allergy specialist. Some life threating reactions are not allergic (blistering skin reactions) and would not be candidates for testing.
Studies have shown the benefits of confirming if a person’s reaction to a medicine was allergic as it offers the opportunity to use good, less expensive medicines that have fewer side effects and complications.
In addition to testing for medicine allergies, the allergy specialists of Advanced Allergy & Asthma Care provide treatment for asthma, nasal allergies, eye allergies, sinus infections, as well as food and skin allergies. Additionally, we treat insect stings and asthma. Feel free to discuss any drug reaction and possible testing with an allergy specialist at ASC. We have locations throughout Fairfield County, CT with offices in Danbury, New Milford, Norwalk and Ridgefield.