What is a drug allergy?
A severe drug allergy is an allergic reaction often characterized by itching, hives, swelling, difficulty breathing, severe stomach/intestinal symptoms, and/or passing out. There are also drug allergies that present solely as rashes or hives. Additionally, there are non-allergic side effects of drugs.
Research has shown that drug allergies are overdiagnosed. Confirmation of a drug allergy is important because drug allergies may result in the use of less appropriate or more expensive drugs with more side effects. Even with a severe drug allergy, after 10 years 80% of people will no longer be allergic.
What is done during an evaluation for drug allergy?
A drug allergy evaluation will typically take anywhere between two and three hours. We care for our patients by using a team approach. The care team includes specialists in allergy and immunology and pharmacy. That means that when you need care, you will see an allergy specialist with or without a pharmacist who will work together to discuss the diagnosis and create a care plan.
During your visit your provider will ask you questions about your drug allergy including the symptoms you had, when they started and what you did for the symptoms (such as taking medication or presenting for evaluation). Following this history your provider may suggest skin testing or a drug challenge.
Skin testing is done on your forearm with salt water (negative control), histamine (positive control), and the medication in question. This is typically a two-step process. The first step involves a scratch test on the skin. The second test is done under the skin (intradermal) with a needle. This testing takes approximately 60 minutes. If testing is negative this is followed by a challenge to the medication in question. If testing is positive your allergy label will be updated with the visit information.
There are some medications which we are unable to test for. In this situation typically a two-step challenge is performed. This involves giving you 10% of a medication and monitoring you for 30 minutes. If you tolerate this well you will be given the full dosage and monitored for two hours thereafter. If you tolerate this challenge you do not have an allergy.