April 26, 2021
3 min. read

Ask a Pharmacist: What Are Drug Allergies?


You’ve just been prescribed a new medication by your doctor and your Medly delivery driver has dropped it off.

It’s time to take your first dose, and you’re curious how your body will react. How can you predict if you’ll have a drug allergy? And what steps should you take if you do?

To learn more about drug allergies and potential treatments, we sat down with Medly’s Director of Clinical Services and board certified pharmacist, Viral Shah.

Read on for his answers to some of our biggest questions about drug allergies.

What are drug allergies

What is a drug allergy?

A drug allergy is the abnormal reaction of your immune system to a prescription, over-the-counter, or herbal medication. Some drugs are more commonly associated with drug allergies than others.

What causes a drug allergy?

A drug allergy occurs when your immune system mistakenly identifies a drug as a harmful substance, after which it will develop an antibody specific to the substance. This can happen the first time you take a drug, but sometimes an allergy doesn’t develop until there have been repeated exposures. When or if you take the drug again, these specific antibodies flag the drug and direct an immune system attack on the substance. Chemicals released by this activity cause the signs and symptoms associated with an allergic reaction.

How can I find out if I’m allergic to any drugs?

An allergist, your provider, or a nurse practitioner may perform a skin test. During this process, a small amount of suspect drug will be introduced to your skin via a tiny needle, an injection, or a patch, to see if your body reacts to the drug. A positive reaction to a test will cause a red, itchy, raised bump which may suggest that you have a drug allergy.

allergic to drugs

What are the signs and symptoms of drug allergy?

The most common signs and symptoms of a drug allergy include skin rash, hives, itching, fever, wheezing, runny nose, and itchy and watery eyes. These reactions can occur hours, days or even weeks after exposure. The most severe drug allergy will often occur within an hour of taking the drug.

What is anaphylaxis?

Anaphylaxis is a rare, life threatening, and serious allergic reaction that occurs within seconds to minutes of drug exposure. It can cause tightening of the airways and throat or swelling of the throat, shortness of breath, or an itchy rash.

Which drugs are commonly associated with allergic reactions?

Antibiotics such as penicillin or sulfamethoxazole, medications used to treat cancer, autoimmune conditions and pain relievers such as aspirin, ibuprofen and naproxen have been commonly associated with allergic reactions.

patient provider

How are allergic drug reactions treated?

Drug reaction without breathing difficulty can be treated by stopping the drug causing the reaction or by treating specific symptoms. Antihistamine such as Benadryl can be used to treat itching, rash and swelling while systemic steroids and NSAIDs (Ibuprofen) can be used to decrease swelling.

Epinephrine in the form of an EpiPen can be used if a patient is wheezing or presenting other signs of trouble breathing. Anaphylactic reaction requires immediate medical care and the patient or family member should call 911 right away.

What are the prevention steps you can take?

Three ways you can help prevent drug allergies:

  • Wear a medical bracelet that identifies drug allergy.
  • Make sure all of your healthcare support team including pharmacists knows about drugs you are allergic to.
  • Keep an EpiPen with you at all times if necessary.

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