Antibiotics are medicines that treat infections caused by bacteria. But they do not work for every illness, and using them when they are not needed carries real risks. Knowing the difference helps you get the right care and keeps these medicines working for the future.
This guide explains what antibiotics do and why they will not help a cold or flu. It also covers antibiotic resistance, common side effects and simple ways to use antibiotics wisely. The aim is to help you have a clearer conversation with your doctor or pharmacist.
What antibiotics actually do
Antibiotics work by killing bacteria or stopping them from multiplying. This gives your immune system the help it needs to clear a bacterial infection. They do nothing to viruses. That single fact explains most of the confusion about when they should be used.
Viruses cause most colds, flu and COVID-19. When you have one of these illnesses, an antibiotic will not shorten it or ease your symptoms. Your doctor will decide whether an infection is likely to be bacterial. That decision is based on a clinical assessment and sometimes on tests.
Why antibiotics will not fix a cold or flu
The Australian Government Department of Health has a simple message on this. Its page antibiotics won’t do for colds and flu explains that antibiotics only fight bacteria. Most people with a viral respiratory infection recover without treatment within 7 to 10 days. That includes colds, flu, RSV and COVID-19.
Some people at higher risk who become very unwell may be prescribed antiviral medicines. These are different from antibiotics. Only a healthcare professional can decide if they are right for you. If you stay unwell or your fever gets worse, it is worth seeing a doctor.
Not every runny nose is a virus either. Spring often brings sneezing and itchy eyes for many people. Our article on how to have a sneeze free spring looks at that season. Antibiotics are not the answer for those symptoms.
What antibiotic resistance means
Antibiotic resistance happens when bacteria change to protect themselves from an antibiotic. Once that happens, the medicine no longer kills them. Healthdirect explains that resistance can occur naturally, but the main cause is antibiotic use. Taking antibiotics when they are not needed, or not taking them properly, both add to the problem.
Resistant infections are harder to treat. People may be sick for longer, have more complications and need more complex care. They may also stay infectious for longer. In some cases resistant infections cause serious illness or death.
The Department of Health describes antimicrobial resistance as one of the biggest threats to human and animal health today. In a worst case, no effective antibiotics would remain. Healthdirect notes that resistance cannot be totally stopped. However, its spread can be slowed by using antibiotics sensibly.
Superbugs explained
The word superbug refers to bacteria that resist many types of antibiotics. These infections are very hard to treat. Healthdirect lists examples such as MRSA and VRE. It also notes that the last antibiotic treatment for gonorrhoea has already started to fail in Australia.
Healthdirect also states that Australia has one of the highest rates of antibiotic use in the world. That is one reason using them wisely matters. Antibiotics are sometimes given to prevent infection around surgery or dental procedures. Australian doctors and nurses are reviewing this practice to help reduce resistance.
Antibiotics around surgery and procedures
If you are planning a procedure, your care team will talk you through any medicines involved. Eye procedures are a good example of planning that starts well before the day. Our posts on laser eye surgery facts and suitability for laser eye surgery cover some of the questions people ask. Ask your surgeon directly about any drops or tablets you will need afterwards.
Common side effects
Like all medicines, antibiotics can cause side effects. Healthdirect lists diarrhoea, nausea, vomiting and thrush in the mouth or vagina as common ones. Ongoing diarrhoea and allergic reactions are less common. Allergic reactions most often show up on the skin.
Signs of an allergic reaction can include hives, a fever of 38°C or higher and difficulty breathing. Anaphylaxis is a severe reaction that usually happens within an hour. If it happens, call triple zero straight away. Nausea and vomiting on their own are side effects, not an allergy.
Many people believe they are allergic to an antibiotic such as penicillin. Healthdirect notes that most antibiotic allergies disappear after a few years. Talk to your doctor or pharmacist about any past reaction before you start a new course. They can help work out what is safe for you.
How to use antibiotics wisely
Healthdirect’s page on antibiotic resistance sets out what each of us can do. Take antibiotics at the right times and for as long as your doctor prescribes. Keep going even if you feel better. Do not take more than prescribed, even if there are tablets left over.
Never share antibiotics with someone else. Their infection may need a different medicine, or none at all. Return any unused tablets to your pharmacy. Do not ask for antibiotics for a cold or flu.
Labels and instructions can be confusing, as medical language often is. Our guide to speech therapy terminology shows how health jargon can trip people up in any field. If anything on your medicine label is unclear, ask your pharmacist to explain it. They are happy to help.
Preventing infections in the first place
The fewer infections we catch, the fewer antibiotics we need. The Department of Health recommends a flu vaccine every year. Stay home when you are sick, and wear a mask if you need to go out. Wash your hands regularly and cough or sneeze into a tissue or your elbow.
Try not to touch your eyes, nose and mouth, especially around people who are unwell. Clean things you touch often, such as phones and door handles. These habits sound simple, but they add up. They protect you and the people around you.
Frequently asked questions
Will antibiotics help me get over a cold faster?
No. Colds are caused by viruses, and antibiotics only work on bacteria. Most people recover from a cold or flu within 7 to 10 days without treatment. Taking antibiotics you do not need can cause side effects and add to resistance.
Should I finish my antibiotics if I feel better?
Healthdirect advises taking antibiotics for the full time your doctor prescribes, even if you feel better. Not finishing a course is one way resistance can develop. If you have concerns about side effects, talk to your doctor or pharmacist. Do not stop or change a course without advice.
What should I do with leftover antibiotics?
Return unused tablets to your pharmacy. Do not keep them for a later illness or give them to anyone else. A future infection may need a different medicine. Your doctor is the best person to decide that.
What is a superbug?
A superbug is a type of bacteria that resists many antibiotics. Examples include MRSA and VRE. These infections are very hard to treat. Using antibiotics wisely helps slow their spread.
This article is general information only and is not medical advice. Please speak with your doctor, pharmacist or a qualified health professional about your own health.