Drug Allergies

Reviewed by Carol DerSarkissian on November 11, 2019

You need your medicine to manage your health. They can make a huge difference in your life. But sometimes, people have an allergic reaction to a medicine.

When you have an allergy, your immune system mistakenly sees something that’s harmless as an invader. Your body responds with certain chemicals, such as large amounts of histamine, to try to get rid of it.

If you think you have a drug allergy, tell your doctor. There may be another treatment you could try instead.


Even in people who aren't allergic, many drugs can cause issues like an upset stomach. But during an allergic reaction, the release of histamine can cause symptoms like hives, a skin rash, itchy skin or eyes, congestion, and swelling in the mouth and throat.

A more severe reaction, called anaphylaxis, may include trouble breathing, blueness of the skin, dizziness, fainting, anxiety, confusion, rapid pulse, nausea, diarrhea, and other serious symptoms.

What Are the Most Common Drug Allergies?

Penicillin and other similar antibiotics are the drugs most people are allergic to.

Other meds commonly found to cause allergic reactions include sulfa drugs, barbiturates, and anti-seizure drugs.


Your doctor will talk to you about your medical history and symptoms. If they think you might be allergic to an antibiotic, such as penicillin, they may give you a skin test to confirm it.

But skin testing doesn’t work for all drugs, and in some cases it could be dangerous. If you've had a severe, life-threatening reaction to a particular drug, your doctor will simply rule out that medicine as a treatment option for you. Getting an allergy test to find out if the severe reaction was a "true" allergic response isn't needed if there are other drug options.


The first goal is to ease your symptoms. For instance, medicines such as antihistamines, and in some cases, corticosteroids, can often control rash, hives, and itching.

For coughing and lung congestion, your doctor may prescribe drugs called bronchodilators (such as albuterol or combivent) to widen your airways.

For anaphylaxis symptoms, you may need a shot of epinephrine, and you definitely need emergency medical care, even if those symptoms stop after you take epinephrine.


Sometimes, doctors use a process called desensitization to treat an allergy to penicillin or other drugs. Over time, you’ll get shots of tiny amounts of penicillin, with increasingly larger amounts until your immune system can handle the drug. You'll probably only get this procedure if there aren't any other medicines that can treat your condition.

If you're severely allergic to certain antibiotics, there should be alternatives that your doctor can prescribe.

How Can I Be Prepared?

If you know you have a drug allergy, tell all your health care providers before you get any type of treatment, including dental care.

It’s also a good idea to carry a card or wear a special bracelet or pendant that identifies your allergy, in case of emergency.

WebMD Medical Reference



FDA: "Avoiding Drug Interactions."

FamilyDoctor.org: "Drug Reactions."

American Academy of Allergy Asthma & Immunology: "Medications and Drug Allergic Reactions: Tips to Remember."


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