Drug Allergy Treatment 101: How to Prevent, Treat, and Diagnose Allergies to Medication

Allergies can be difficult to deal with. This is true whether they’re caused by outdoor triggers, such as dust or pollen, or foods, such as soy or peanuts. Medications or supplements you take may even be at fault in some cases.

Like other allergies, we can’t control what medications our bodies are allergic to. But we can control how we respond to allergic reactions. It’s important to be able to spot the symptoms of an allergic reaction and know what to do if you experience one.

What is a drug allergy?

A drug allergy is a negative reaction that your immune system may have to a medication. This can occur even if you take your medication properly, or as prescribed. Your body sees the medication as a harmful “invader,” and the reaction you experience is caused by your body trying to fight off the medication.

Symptoms of an allergic reaction to medication

There are different symptoms you may experience if you’re having an allergic reaction to a medication. Some symptoms are mild and pass quickly, while others are more intense. It all varies by situation.

Some of the more common symptoms include:

• Rashes or hives

• Itching

• Nausea

• Diarrhea

• Wheezing

In more severe cases, you may experience anaphylaxis. This is a serious reaction that involves different parts of your body. You may experience symptoms similar to the ones above, but you may also endure more serious symptoms, such as vomiting and facial or throat swelling. Anaphylaxis warrants emergency medical care.

Drug allergy timing

Several allergic reactions are immediate allergic reactions. Symptoms typically start to show within minutes to hours of starting a medication.

“Delayed” allergic reactions, by comparison, may begin days to weeks after starting a new medication. These are relatively common, and they can range from mild to severe in intensity. Some serious examples of a delayed allergic reaction include drug rash with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN).

EXPERT PICKS: WHAT TO READ NEXT

• Think you have a drug rash? Learn more about common medication allergies and how to identify what a drug rash may look like.

• Treating allergic skin reactions: Read about over-the-counter medications and home remedies that may be used to treat mild allergic skin reactions.

• Concerned about anaphylaxis? Find out how you can prevent and treat episodes of anaphylaxis.

What are the most common drug allergies?

A variety of medications can trigger drug allergies. Some of the most common culprits include:

• Antibiotics, such as amoxicillin (Amoxil)

• Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs)

• Anti-seizure medications, such as phenytoin (Dilantin)

• Sulfa drugs, such as sulfamethoxazole / trimethoprim (Bactrim) and furosemide (Lasix)

• Monoclonal antibodies, such as dupilumab (Dupixent)

• Chemotherapy medications, such as cyclophosphamide (Cytoxan)

• Contrast dyes, commonly used in procedures like CT scans and MRIs

How are drug allergies diagnosed?

Drug allergies can be difficult to spot proactively. In many cases, a drug allergy is diagnosed and confirmed by a healthcare professional after you experience a reaction.

In some cases, it’s possible to receive a skin test from an allergy specialist to potentially find out what medications you may be allergic to. But this is only an option for a few medications, such as penicillin antibiotics and some chemotherapies. Other allergies that may not be tested using a skin test may be detected using a blood test. Your healthcare team will collect a blood sample from you and then test it for potential allergies.

Another option for some medications is a drug challenge test, where an allergist will give you small amounts of a medication to see how your body responds to it.

If you have concerns about a potential drug allergy, talk to a healthcare professional. They can tell you more about allergy testing and if it’s an option for you.

Drug allergy treatment

Treating an allergic drug reaction is generally based on how severe your reaction and symptoms are. If your symptoms are mild, you may be able to manage them on your own. But if you’re experiencing anaphylaxis or another serious reaction, it’s important to call 911 or seek emergency medical care immediately. Stop taking the offending medication if you know what it is.

If you have a history of allergic reactions, speak with your healthcare team to find out what medications you can have on hand to treat future allergic reactions.

Medications that treat drug-related allergic reactions

A variety of medications can help manage allergic reactions. Some of them are available over the counter (OTC) and can be used for milder situations. Others are prescribed or administered by your healthcare team when your reaction is more severe.

Antihistamines are primarily available OTC. They can help with itching, rashes, and other mild symptoms. Some examples include diphenhydramine (Benadryl), fexofenadine (Allegra), and cetirizine (Zyrtec).

Bronchodilators are inhalers that help address difficulty breathing or wheezing. These medications are typically only available with a prescription. A few bronchodilators are available, but albuterol (Ventolin HFA) is a common, fast-acting choice.

Corticosteroids are available OTC in topical forms, such as creams and ointments. There are other forms that are prescription only, such as tablets and injections. These medications are designed to help lessen swelling or inflammation you’re experiencing from a drug allergy. Examples include:

• Topical steroids, such as hydrocortisone (Cortizone 10)

• Oral steroids, such as prednisone

• Injectable steroids, such as triamcinolone (Kenalog-10)

Epinephrine, also known as EpiPen, AUVI-Q, and neffy, is typically prescribed when you have a history of anaphylaxis. It can also be prescribed if you’re expected to have a severe reaction based on the results of skin or blood allergy tests. If you’re exposed to a medication you’re allergic to and think a severe reaction is underway, you should administer epinephrine as soon as possible. Call 911 or seek medical care right away, too.

Preventing allergic reactions: How to communicate drug allergies to your care team

If you’ve experienced an allergic reaction to a medication in the past, it’s crucial to inform your healthcare team. This includes your primary care provider (PCP), pharmacist, and any specialists you may see. You can speak with them in person, over the phone, or tell them through an online patient portal (if they have one). They can document the allergy in your medical record.

Let them know which medication(s) you potentially experienced a reaction to. Also make sure to describe what your symptoms were, how long your symptoms took to set in, and how severe your reaction was. This will help prevent them from re-prescribing that same medication or prescribing you any similar medications that may also cause a reaction.

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Written by:

Jason Do, PharmD Candidate

Jason Do, a Doctor of Pharmacy (PharmD) candidate, has worked primarily in community pharmacy at CVS Pharmacy and the Phoenix Children's Hospital outpatient pharmacy. He also has experience in hospital pharmacy through Dignity Health.

Reviewed by:

Celine Kwan, PharmD Candidate

Celine Kwan, a Doctor of Pharmacy (PharmD) candidate, has experience working in both community and hospital pharmacy settings. Additionally, she worked for an insurance company and a market access agency.

Reviewed by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

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