Penicillins and penicillin allergy

Key information about penicillins and penicillin allergy

A penicillin allergy is a rare and severe reaction of your immune system to a penicillin-containing antibiotic.
Most people who think they have a penicillin allergy do not. If you think you have a penicillin allergy, talk with your doctor, pharmacist or nurse.
Read about penicillin allergies and what to do if you are allergic to penicillin.

Penicillins are a group of antibiotic medicines commonly used to treat infections (eg, 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, eg, side effects or antibiotic resistance. They don't work for infections caused by viruses (eg, colds, flu or COVID-19) – no antibiotic does.

Examples of penicillin antibiotics available in Aotearoa New Zealand

Penicillins available in Aotearoa New Zealand	Also called
Amoxicillin	Amoxil® Alphamox®
Amoxicillin + clavulanic acid	Augmentin ® Curam® Amoxiclav®
Benzathine penicillin	Bicillin LA®
Flucloxacillin	Flucloxacillin (AFT)®
Phenoxymethylpenicillin	Cilicaine VK® Phenoxymethylpenicillin (AFT)®
Piperacillin with tazobactam	Pip Taz (AFT)® Piperacillin/Tazobactam (Kabi)®
Procaine benzylpenicillin	Cilicaine®
Pivmecillinam hydrochloride	Selexid®

A 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.

Image credit: Healthify He Puna Waiora

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 (eg, 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 making sure your online clinical records are accurate and using non penicillin containing antibiotics when you need treatment.

There are many antibiotics that don't contain penicillin. These can be used if you have a true penicillin allergy.

If you have an infection that needs antibiotics, it's 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's the best treatment for you. So don’t limit your treatment choices – find out for sure whether you are allergic to penicillin.

Read more about medicines and side effects and reporting a reaction you think might be a side effect.

Antibiotics
Antibiotic resistance and prevention
Medicines and side effects
Anaphylaxis

Severe Allergic Reactions (Anaphylaxis)(external link) to Medicines Medsafe, NZ