Most colds, coughs and sore throats don’t need antibiotics, because viruses cause them and antibiotics only kill bacteria. A cold usually settles in 1 to 2 weeks and a cough in 3 to 4 weeks with or without a prescription, so the real question is not “should I take antibiotics?” but “is there a sign this has turned into something bacterial or serious?”
This guide gives you the usual timelines, the specific signs that change the answer, and what actually eases symptoms while you wait. It matters more than usual this month: in late October the US Centers for Disease Control and Prevention (CDC) released a new estimate of drug-resistant infections, and 18 to 24 November is World AMR (antimicrobial resistance) Awareness Week.
Why antibiotics don’t help a cold or flu
Antibiotics work by attacking structures that bacteria have and viruses don’t. The CDC is blunt about it: antibiotics do not work on viruses, and that includes colds, flu, most sore throats and most cases of bronchitis. The NHS says the same about colds: GPs don’t recommend antibiotics because they won’t relieve your symptoms or speed up recovery.
So when someone says “I took antibiotics and felt better on day 5,” the infection was usually getting better on its own anyway.
Even some bacterial infections clear without them. The CDC notes that many sinus infections and some ear infections don’t need antibiotics, and the NHS antibiotics page says they’re no longer routinely used for chest infections, ear infections in children or sore throats.
How long common infections usually last
A lot of antibiotic requests come from people who think their illness is going on “too long.” Here are the normal timelines, so you can judge that more fairly.
| Illness | Usual duration | Antibiotics usually needed? | Check with a doctor if |
|---|---|---|---|
| Common cold | 1 to 2 weeks | No | No better after 10 days, fever over 3 days, short of breath |
| Cough (acute) | 3 to 4 weeks | No, in most cases | Lasts more than 3 weeks, coughing blood, chest pain |
| Sore throat | About 1 week | Only if a test or doctor confirms strep | No better after a week, can’t swallow, drooling |
| Ear infection | Most clear within 3 days, sometimes up to a week | Sometimes | No better after 3 days, swelling behind the ear, fluid from ear |
| Sinusitis | Varies; mostly viral | Only in specific situations (see below) | Over 10 days with no improvement, or worse after getting better |
Timelines are from the NHS pages on cough, sore throat, colds and ear infections. The key point is that a cough lasting 2 or 3 weeks after a cold is normal. It’s annoying, but it isn’t a sign of a bacterial infection by itself.
Does green or yellow mucus mean you need antibiotics?
No. This is probably the most common myth. Mucus turns yellow or green because of immune cells fighting the infection, and that happens with viruses too. The CDC’s guidance for doctors states that coloured sputum does not indicate a bacterial infection, and it advises against routine antibiotics for acute bronchitis regardless of how long the cough lasts.
What does matter is how unwell you feel overall, your breathing, and the direction things are going: slowly better, or worse.
When a sore throat might need antibiotics
A small share of sore throats are caused by group A streptococcus (“strep throat”). These can be treated with antibiotics. Doctors look for a pattern rather than one symptom. In the US, guidance uses the Centor criteria: fever, white patches or pus on the tonsils, tender swollen glands at the front of the neck, and no cough. If you have two or more, the CDC recommends a rapid strep test, and antibiotics aren’t recommended if that test is negative.
In the UK, a pharmacist can assess a sore throat for anyone aged 5 or over. Wherever you live, taking a leftover or over-the-counter antibiotic “just in case” is exactly the habit that drives resistance.
A sore throat with a runny nose, cough and hoarse voice points strongly to a virus.
Sinus infection: the 10-day rule and “double sickening”
Most sinus symptoms after a cold are viral and clear without treatment. The CDC lists three patterns that make a bacterial sinus infection more likely:
- Persistent: symptoms lasting more than 10 days with no improvement at all.
- Severe: a fever of 39°C (102°F) or higher, with thick nasal discharge or facial pain, for 3 to 4 days in a row at the start.
- Worsening (“double sickening”): you start to recover from a cold after 5 or 6 days, then get a new fever or worse symptoms.
Even then, for an otherwise healthy adult with mild symptoms, a doctor may suggest waiting a few days first. Our guide to treating sinusitis at home and when antibiotics are needed covers sinus care in more detail.
Antibiotics have real downsides
Taking an antibiotic you don’t need isn’t harmless. The NHS lists common side effects including feeling or being sick, bloating, indigestion and diarrhoea. Rarely, people have a serious allergic reaction. In children, the CDC says side effects from antibiotics are the most common cause of medication-related emergency department visits.
Antibiotics also wipe out helpful gut bacteria, which can let Clostridioides difficile (C. diff) take over and cause severe diarrhoea.
Then there’s resistance. Every course gives bacteria in your body a chance to adapt. The World Health Organization says bacterial antimicrobial resistance was associated with more than 4.7 million deaths worldwide in 2021, and that misuse and overuse of antimicrobials drive it. The CDC’s 2026 threats update estimates 9.7 million infections and 50,800 deaths a year in the US from the bacteria and fungi it tracks. The CDC changed its methods for this update, so don’t compare the figure directly with older reports, but either way it’s a large number.
What actually helps while a virus runs its course
None of these will cut a cold short, but they make the days easier:
- Rest and fluids. Stay home while you have a fever or feel too unwell for normal activities.
- Paracetamol (acetaminophen) or ibuprofen for fever, sore throat and aches. Follow the dose on the pack, and check that combination cold products don’t double up on paracetamol.
- Honey and lemon in warm water may soothe a cough. The evidence is limited, and never give honey to a baby under 1 year.
- Warm salty water gargles for a sore throat in adults (not for young children).
- Pharmacy lozenges or sprays for throat pain.
- Pelargonium, a herbal cough remedy, is listed by the NHS as an option for people 12 and over.
If you’re not sure whether it’s a cold, flu or COVID, our flu symptoms guide for the 2026 season explains how to tell them apart and when antiviral medicine is used for flu. Antivirals are a different thing from antibiotics and have to be started early.
If you are prescribed antibiotics
Sometimes you genuinely need them: strep throat, a urinary tract infection, whooping cough, bacterial pneumonia. In that case:
- Take them exactly as the prescriber or pharmacist tells you, including the number of days. Some courses are now shorter than they used to be, so follow your own prescription rather than what a friend was given.
- If you miss a dose, take it when you remember unless the next dose is nearly due. Never take a double dose.
- Don’t save leftovers for next time or share them. The wrong antibiotic, or the wrong dose, can do more harm than good.
- Tell the doctor about any allergy, pregnancy or other medicines. If you’re pregnant, see our article on antibiotics in pregnancy.
If a doctor says you don’t need antibiotics, it’s fine to ask, “What should make me come back?” A good answer is a clear set of warning signs and a time frame.
When to see a doctor
Book a GP or doctor appointment if:
- a cough lasts more than 3 weeks, or you’re losing weight without trying
- a cold isn’t improving after 10 days, or a fever lasts more than 3 days
- a sore throat hasn’t improved after a week, or you get sore throats often
- earache hasn’t improved after 3 days, or a baby under 12 months seems to have an ear infection
- you have diabetes, a weakened immune system, or a long-term heart or lung condition and feel worse than usual
- you start to recover, then suddenly get worse again
Older adults can have pneumonia with few chest symptoms, sometimes just confusion or weakness. See early signs of pneumonia in older adults if you’re caring for a parent with a “cold” that isn’t behaving normally.
Get emergency help if…
Call your local emergency number (911 in the US, 999 in the UK, 112 in the EU and India) if someone:
- is struggling to breathe, or makes a high-pitched noise when breathing in
- can’t swallow or is drooling
- has chest pain or is coughing up blood
- is confused, very drowsy or hard to wake
- has blue or grey lips, or a rash with swelling of the face or throat after taking a medicine
Frequently asked questions
Can a cold turn into a bacterial infection?
Yes, occasionally. A cold can lead to a bacterial sinus infection, ear infection or pneumonia. The clue is a change in direction: getting worse after you’d started to improve, a new high fever, or breathing trouble. A slow, lingering cough on its own isn’t that clue.
Will antibiotics stop my cold from spreading to my family?
No. Antibiotics don’t affect cold or flu viruses, so they won’t make you less contagious. Handwashing for at least 20 seconds, covering coughs and staying home while you have a fever help more.
Is it OK to take leftover antibiotics from last time?
No. It’s probably the wrong drug for this illness, it’s likely not a full course, and it adds to resistance. Return unused antibiotics to a pharmacy for disposal.
Do I need to finish the whole course of antibiotics?
Take them for as long as your prescriber or pharmacist says. Course lengths have been getting shorter for some infections, so don’t stop early or carry on longer on your own judgement. Ask if you’re unsure.
Can I ask my pharmacist instead of a doctor?
Often, yes. In the UK, pharmacists can assess and treat several common infections, including sore throats and ear infections in children aged 1 to 17. In many countries a pharmacist can also tell you whether you need to see a doctor.
This article is for general information and is not a substitute for advice from a doctor. If you have symptoms or a health condition, please consult a qualified healthcare professional.
