Most Common Drug Allergies

Last updated: March 2022

People can be allergic to certain drugs. Their immune system sees the drug or something in it as a threat. Allergy symptoms may appear when the immune system attempts to protect the body from a drug the immune system thinks is harmful.1-5

Allergic reactions make up about 5 to 10 percent of the reactions people have to drugs. Other types of reaction to drugs include interactions with other drugs, sensitivity, and side effects.2,4,5

Some people are more likely to have drug allergies. This includes adults (not seniors), women, and people with certain genes or health issues, such as a viral infection. Some drugs are more likely to cause an allergic reaction. A person with one drug allergy is also more likely to have other drug allergies.2,4,5

Your drug allergies can become less severe over time. But you may not know this change has happened if you avoid the drug. Studies show that 9 out of 10 people who have had an allergic reaction to penicillin may be able to take the drug later in life.1,4,5

Drugs most likely to cause an allergic reaction

Penicillin and related antibiotics are the drugs that cause most allergic reactions in people with drug allergies. Drugs put on the skin or injected are more likely to cause an allergic reaction than drugs taken by mouth.1-5

Other drugs that sometimes cause allergic reactions include:1-5

  • Chemotherapy drugs
  • Drugs for high blood pressure, such as ACE inhibitors
  • Seizure drugs
  • Drugs used in imaging tests to increase contrast so the image can be more easily read
  • Monoclonal antibodies
  • Non-steroidal anti-inflammatory drugs (NSAIDs), such as Tylenol or ibuprofen
  • Sulfa drugs
  • Thyroid drugs
  • Vaccines

Symptoms of drug allergies

The symptoms of drug allergies may appear right away, but not always. An allergic reaction can occur days or weeks later. You can also start having an allergic reaction even if you have taken the same drug before without a problem.1,2

Drug allergies tend to affect the skin. But they can affect other organs too. Common symptoms of a drug allergy include:1-5

  • Trouble breathing, tightness in the chest or throat
  • Coughing, wheezing
  • Dizziness
  • Itching, rash, hives
  • Runny nose
  • Swelling
  • Vomiting

More serious reactions to drugs can also occur. Among these are Stevens-Johnson syndrome and toxic epidermal necrolysis. With these reactions, blisters may form on eyes, lips, and other parts of the body.2,3

Some people even develop anaphylaxis in response to certain drugs. Anaphylaxis is a sudden and dangerous reaction that affects breathing and heart function. When a person is having an anaphylactic reaction, they can go into shock and die.1-5

Getting your drug allergies diagnosed

A doctor can diagnose a drug allergy after giving you a thorough exam. During this exam, the doctor will ask about:3-5

  • Your symptoms
  • Your health history
  • What drugs you take
  • What supplements and vitamins you take

Tests can help your doctor figure out what you may be allergic to. For instance, a skin prick test will detect a penicillin allergy. A blood test can confirm some reactions, like drug rash with eosinophilia and systemic symptoms (DRESS).1,3-5

Your doctor may use an oral drug challenge to confirm your drug allergy. In this challenge, you receive small, increasing amounts of the drug in the presence of the doctor. The doctor watches you to see if you react. They can treat any symptoms that arise or – if needed – end the challenge.1,3-5

Treating your drug allergies

The main way to treat a drug allergy is to not use the drug that is causing you to react. If you have allergic symptoms after taking a drug, contact your doctor. The doctor may tell you to take an antihistamine, corticosteroid, or NSAID. Some of these you can buy from any grocery or drugstore. Others need a prescription.1-5

You can also ease less serious reactions without taking additional drugs. Cool baths, compresses, and showers can ease mild skin symptoms. Wearing light, loose clothes and using soap without dyes and scents may bother your skin less.3

Severe symptoms that affect your breathing demand quick action. If you have an injection of epinephrine, use it. Otherwise, go to the closest emergency department, hospital, or urgent care center. Doctors there can give you epinephrine.1,3-5

If you are allergic to a drug you need, your doctor may suggest drug desensitization or tolerance treatment. Like with an oral challenge, the doctor will give you the drug in small doses and observe you for some time. The doctor will increase the dose little by little if you can handle it. This treatment may help lessen your reaction to the drug.1,3-5

Managing your drug allergies

There are several things you can do to prevent an allergic reaction or to handle the reaction when it occurs. These include:1-5

  • Avoiding drugs you know you are allergic to
  • Using another drug in place of the one you are reacting to
  • Telling your doctor, pharmacist, and other healthcare providers about your drug allergies and past reactions
  • Keeping a list of the drugs, supplements, and vitamins you take and sharing the list every time you see your healthcare provider
  • Making sure your medical records include your drug allergies
  • Wearing a medical alert bracelet, necklace, or tag to let first responders know about any allergies you have

Talk to your doctor if you think you might have a drug allergy. Your doctor may refer you to an allergy or skin expert who can provide advanced testing and care.

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