Penicillins and penicillin allergy

Penicillins are a group of antibiotics used to treat infections caused by bacteria. Penicillin allergy is often misleading because 9 out of 10 people who think they have a penicillin allergy do not.

On this page, you can find the following information:

What are penicillins?

Penicillins are a group of antibiotic medicines commonly used to treat infections such as urinary tract, skin and chest infections that are caused by bacteria.

Penicillins are the safest and most effective antibiotics for many infections. When compared to other groups of antibiotics, they cause fewer problems like side effects or antibiotic resistance.  They do not work for infections caused by viruses such as colds, flu or COVID-19. No antibiotic does.

Which penicillins are available in Aotearoa New Zealand?

Penicillins available in Aotearoa New Zealand Also called
  • Amoxil®
  • Alphamox®
Amoxicillin + clavulanic acid
  • Augmentin ®
  • Synermox®
  • Curam®
  • m-Amoxiclav®
 Benzathine penicillin
  • Bicillin LA
  • Staphlex®
  • Flucloxacillin (AFT)®
  • Cilicaine VK®
  • Penicillin V®
  • Phenoxymethylpenicillin (AFT)®
Piperacillin with tazobactam
  • PiperTaz
  • Tazocin EF
  • PipTaz
Procaine benzylpenicillin
  •  Cilicaine

What is a penicillin allergy?

Penicillin allergy is a rare and severe reaction of your immune system to a penicillin-containing antibiotic. Severe penicillin allergy is also called a true penicillin allergy.

Signs and symptoms of severe penicillin allergy include anaphylaxis, (an immediate life-threatening reaction), an itchy rash, difficulty breathing, and swollen lips or tongue. These usually happen within 60 minutes of taking a dose. True penicillin allergy is rare – fewer than 5 out of 10,000 people are allergic to penicillin.

Reactions like nausea (feeling sick), diarrhoea (runny poo) or thrush often occur with antibiotics but are side effects not allergies. Sometimes these symptoms could be from your infection. Side effects are not nice and they usually pass once you finish your antibiotics. Read more about medicines and side effects.

How common is penicillin allergy?

True penicillin allergy is rare (fewer than 5 out of 10,000 people). Many people who report having a penicillin allergy can actually take penicillin safely.

Is penicillin allergy a lifelong condition?

No. Our immune systems change with time and most people lose their penicillin allergy over time, even in people with a history of severe reaction such as anaphylaxis. Penicillin allergies often disappear within 10 years of the initial reaction.

Is penicillin allergy genetic?

You do not need to avoid penicillin if your family/whānau member is allergic to penicillin or drugs in the penicillin family. 

What can I do if I think I have a penicillin allergy?

If you think you have a penicillin allergy, talk with your doctor, pharmacist or nurse.

  • 1 out of 2 adults (half) can have their penicillin allergy label removed from their medical record after their healthcare team has asked some questions about the allergy and their medical history.
  • Sometimes, further tests (like giving a very small test dose of penicillin under medical supervision) might be needed to work out if you have a true penicillin allergy.
  • If you are one of the few people who have a true penicillin allergy, your healthcare team will help keep you safe. This will include ensuring your online clinical records are accurate and using non penicillin containing antibiotics when you need treatment.

What about using other antibiotics?

There are many antibiotics that do not contain penicillin. These can be used if you have a true penicillin allergy.  

If you have an infection that needs antibiotics, it is important to have the most effective antibiotic to treat it. If you can take penicillin it will widen the range of antibiotics your doctor can choose from when deciding what is the best treatment for you. So don’t limit your treatment choices – find out for sure whether you are allergic to penicillin. 

Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product


  1. Challenge your penicillin allergy New Zealand Antimicrobial Stewardship & Infection Pharmacist Expert Group (NAMSIPEG)
  2. Penicillin allergy FAQ American Academy of Allergy Asthma and Immunology, 2020
Credits: Sandra Ponen, Pharmacist. Reviewed By: Maya Patel, Pharmacist, Auckland Last reviewed: 16 Nov 2021