Drug Allergy


Photo of Consumer with medicine at pharmacy

What is a drug allergy?

If certain medications make your skin bloom with hives, cause light-headedness, nausea, difficulty breathing or stomach cramps, or make your throat or mouth swell, it could be the result of a drug allergy. Symptoms can begin within moments of ingesting a medication or up to several hours later.

Medications that most often cause a reaction include:

  • Antibiotics
  • Aspirin and non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen
  • Drugs used in anesthesia
  • Insulin (rarely)
  • Chemotherapy drugs

Penicillin, an antibiotic, is the most common cause of drug-induced anaphylaxis. It causes approximately 400 deaths per year.

The most severe allergic reactions to medications usually happen when the medication is given as a shot or intravenously (directly into a vein).

Not every reaction to a medication is a drug allergy. An allergy is an IgE mediated response by the body to an allergen. Some reactions to medications are considered intolerances – where the body doesn’t mount an allergic response, it simply can’t process the medication well. Medications can also produce side effects, which again, aren’t allergies.

What are the symptoms of a drug allergy?

If you develop flushing or hives within a few hours of taking a medication, call a board-certified allergist. If symptoms are severe and involve multiple body organs – a skin rash, respiratory problems and/or digestive issues – it could be anaphylaxis. Call 911 and go to the emergency department immediately. Then you’ll need to schedule a visit with the allergist and get tested for a drug allergy.

If the diagnosis is confirmed, ask the allergist to do the following:

  • prescribe you two epinephrine auto-injectors
  • make a list of safe medications
  • work with you to create an Allergy and Anaphylaxis Emergency Plan for treating as well as preventing future reactions.

What do you need to know about penicillin allergy?

Penicillin is the most common drug allergy and true penicillin allergy is serious – it kills 400 people a year. Anyone who is allergic to one type of penicillin should be considered allergic to all penicillin and should avoid the entire medication group. This includes the more than 15 chemically related drugs such as ampicillin, amoxicillin, amoxicillin-clavulanate and methicillin.

Up to 10 percent of people report being allergic to penicillin, according to the Centers for Disease Control and Prevention (CDC). However, recent studies reveal most people who believe they’re allergic to penicillin may actually be able to safely use it – either because they never were truly allergic or because they lost sensitivity over time.

An allergic reaction to penicillin in childhood does not automatically predict a reaction as an adult. Studies show only about 20 percent of people will be allergic to penicillin 10 years after their initial allergic reaction if they are not exposed to it again during this time period.

Should you test for a penicillin allergy?

Avoiding penicillin without an allergy diagnosis is not the best idea. Alternative antibiotics to penicillin – often called “broad spectrum” – may be less effective in treating an infection, may cause unwanted side effects or may be more expensive. Don’t limit your treatment options – find out for sure whether you’re allergic.

The process is simple. First, the patient undergoes a series of skin prick tests using gradually increasing amounts of penicillin. A raised wheal at the site of the prick indicates allergy.

If the tests are negative, the next step is an oral challenge – drinking a tiny dose of liquid penicillin to see if you are allergic.. Testing should only be conducted by an allergist trained to recognize and treat potential allergic reactions.

If you think you are allergic to penicillin, see a board-certified allergist for testing. Don’t wait until you’re in a medical emergency.

If you are allergic to penicillin, talk with your physician and pharmacist before taking any new medicine to confirm it’s not penicillin-based.

Visit Our Other Pages for More Food Allergy Information.

Ask the Allergist:
Food Allergy

Food Allergy Facts

Food Allergy Articles

Food Allergy
Online Store