What is penicillin?

Penicillin is both the name of a single antibiotic and the name of a widely used group of antibiotic medicines.

Penicillin is used to treat infections caused by certain types of bacteria.

It does not work on viral infections (such as colds and flu or COVID-19).

How does penicillin work?

Penicillin works by breaking down the cell walls of bacteria. This weakens the bacteria and helps your body’s natural immune system fight the infection.

Penicillin works on many types of bacterial infections, but not if the bacteria is resistant (not susceptible) to it.

What is penicillin used for?

Your doctor might prescribe you a type of penicillin if you have a:

• skin infection
• dental infection
• ear infection
• an infection of the nose, throat or lungs
• urinary tract infection (UTI)

Penicillin may also be prescribed for other types of bacterial infections.

Tell your doctor or other prescriber if you have had an allergic reaction to any antibiotics in the past.

What types of penicillin are available?

Penicillin is both the name of a single antibiotic and the name of a group of antibiotics.

Other types of penicillin medicine include:

• amoxicillin
• amoxicillin/clavulanic acid
• ampicillin
• benzylpenicillin
• benzathine benzylpenicillin
• dicloxacillin
• flucloxacillin
• phenoxymethylpenicillin (Penicillin V)
• piperacillin

What should I do if I cannot get my antibiotics?

Currently, there is a shortage of some antibiotics in Australia.

If you can’t get the medicine that you need, speak to your pharmacist or doctor. They can advise on the alternatives.

For more information, visit the Therapeutic Goods Administration (TGA).

What are the possible side effects or risks of penicillin?

All medicines have side effects, as well as benefits.

Side effects

The common side effects of penicillin are usually mild — these include:

• diarrhoea
• nausea
• vomiting
• itch — without a rash
• vaginal itching and discharge — especially if you are using penicillin for a long time

Penicillin allergy

If you think you or someone you know is experiencing anaphylaxis, use the adrenaline autoinjector immediately. Then call triple zero (000) and ask for an ambulance. Follow an ASCIA allergy action plan, if you have one.

Many people who say they are allergic to penicillin don’t actually have a true allergy. Their symptoms might have been caused by side effects.

A true penicillin allergy is a special type of reaction from your immune system.

Penicillin allergy can lead to anaphylaxis. Anaphylaxis is a severe, life-threatening allergic reaction. About 1 in 100 people has an allergy to penicillin.

Signs that you might have a penicillin allergy include:

• skin rashes or hives
• airway swelling
• difficulty breathing due to a severe allergic reaction (anaphylaxis)
• a sudden drop in blood pressure

If you have a penicillin allergy:

• you will need to avoid taking it in future
• you might also be allergic to other types of penicillin and some other antibiotics

You should:

• wear a medical alert bracelet
• always tell your doctor, dentist and other health workers about your allergy
• make sure it is recorded on your My Health Record, in your doctor's medical records and in any hospital records.

Your doctor might refer you for tests to confirm your allergy.

When should I see my doctor?

If you think you or someone you know is experiencing anaphylaxis, use the adrenaline autoinjector immediately. Then call triple zero (000) and ask for an ambulance. Follow an ASCIA allergy action plan, if you have one.

Penicillin allergy can lead to anaphylaxis, a severe, life-threatening allergic reaction.

You should go to the nearest emergency department immediately if you experience any serious signs of penicillin allergy, such as:

• skin rashes or hives
• airway swelling
• difficulty breathing due to a severe allergic reaction (anaphylaxis)
• a sudden drop in blood pressure

You should see your doctor if you get a rash while taking penicillin — stop taking it — and talk to your doctor before taking any more.

See your doctor if you are taking penicillin and any of these common side effects are troubling you:

• diarrhoea
• nausea
• vomiting
• itch — without a rash
• vaginal itching and discharge — especially if you are using penicillin for a long time

You should also see your doctor if your infection is not improving while you are taking penicillin medicines.

Are there any alternatives to this medicine?

There are other types of antibiotics that you can take if you are allergic to penicillin or if penicillin isn’t available.

Ask your doctor which other medicines would be appropriate for your condition.

Resources and support

The Australasian Society of Clinical Immunology and Allergy (ASCIA) has more information about penicillin allergy.

Call 1300 MEDICINE (1300 633 424) for information about penicillin and other medicines.

You can call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with you 24 hours a day, 7 days a week.

Languages other than English

The National Antibiotic Allergy Network has information on antibiotic allergies and side effects in languages other than English.