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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 these antibiotics. It can range from mild to serious. Common reactions include rashes and swelling. But a severe reaction can cause trouble breathing or other serious problems. This can be deadly if not treated right away.

If you are allergic to penicillin, you may also react to antibiotics like it. These include ampicillin and amoxicillin. Ask your pharmacist or doctor about these medicines.

Many people who believe that they have an allergy to penicillin don't have it. They may have a side effect instead. Tests can show if you have an allergy or a side effect.

You're more likely to have a true penicillin allergy if you've had:

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

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. This is called anaphylaxis. It 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, you probably won't have a severe reaction if you take penicillin again.

A severe reaction can include all of the symptoms of a mild reaction, plus:

  • Severe dizziness.
  • Trouble breathing.
  • A 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.

To treat a mild reaction, you can also:

  • Take a cool shower or apply a cool compress.
  • Wear lightweight clothes that don't bother your skin.
  • Avoid strong soaps and detergents. They can make itching worse.

For a severe reaction, you may need a shot of epinephrine. Some 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 the test comes back 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 advice line (811 in most provinces and territories) 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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