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Learning About Penicillin Allergy

What is a penicillin allergy?

A penicillin allergy is an allergic reaction that your body has to penicillin antibiotics. The reaction can range from mild to serious. Common allergic reactions include rashes and swelling. But a severe allergic reaction can cause trouble breathing. This can be deadly if not treated right away.

A severe reaction is more likely if you have had:

  • A positive skin test for penicillin allergy.
  • Hives that appeared right after you took the medicine.
  • A bad reaction to penicillin in the past.

People who have a penicillin allergy also may react to similar antibiotics. These include ampicillin and amoxicillin. Ask your pharmacist or doctor about these medicines.

Many people who believe that they have an allergy to penicillin do not. They may have a mild side effect, rather than an allergic reaction. There are tests that will confirm if you have a penicillin allergy or if it is a side effect.

What are the symptoms?

A mild reaction can cause:

  • A mild rash.
  • Hives.
  • Swelling of your lips, tongue, or face.
  • Itching.

In rare cases, an allergy to penicillin can cause a severe allergic reaction (called anaphylaxis) that can be deadly. Severe reactions usually happen within an hour after you take the medicine. If you had a rash with red, blotchy spots that showed up a few hours or days after you took penicillin in the past, it is unlikely that you will have a severe reaction to penicillin if you take it again.

A severe reaction can include all of the symptoms of a mild reaction as well as:

  • Severe dizziness.
  • Trouble breathing.
  • Rapid or weak pulse.
  • Loss of consciousness.
  • Diarrhea, nausea, or vomiting.

If you take penicillin and then get raised bumps on your skin, have trouble breathing, or have other symptoms of anaphylaxis, call 911 or other emergency services right away.

How is it treated?

The first thing to do to treat a penicillin allergy is stop taking the medicine.

A mild reaction often can be treated with over-the-counter antihistamines. These medicines stop swelling and itching.

Some people may need prescription medicine.

You also can treat a mild reaction by:

  • Taking a cool shower or applying a cool compress.
  • Wearing lightweight clothes that don't bother your skin.
  • Not using strong soaps and detergents. They can make itching worse.

A shot of epinephrine is needed for severe reactions. Sometimes people also get antihistamines and other medicine in a vein.

If you have any reaction to penicillin, let your doctor know right away. There are tests that will confirm if you have a penicillin allergy. If it's positive, tell people who care for you that you have a penicillin allergy.

It's also a good idea to wear medical alert jewellery that lists your allergies.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.

Where can you learn more?

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Care instructions adapted under license by your healthcare professional. If you have questions about a medical condition or this instruction, always ask your healthcare professional. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.