Do You Need Antibiotics for a Sinus Infection?
Honest UK guidance on the 10-day rule, the green mucus myth, and what actually works.
Part of our Sinusitis condition guide.
Here's the headline: NICE guideline NG79 is blunt about it—don't offer an antibiotic for a sinus infection that's been going on for less than 10 days. It sounds harsh when you're the one feeling rough, but acute sinusitis takes a solid two to three weeks to shift. Those first 10 days being unpleasant? That's the illness taking its normal course, not your body failing you.
Need a proper assessment without the GP queue?
Access Doctor is a UK online doctor and GPhC-registered pharmacy. Our pharmacist prescribers review your symptoms and history to decide if you actually need an antibiotic—or, more often, if a steroid spray would do the trick.
View Sinusitis Treatments →The short answer (no fluff)
Honestly? Probably not. Most sinus infections are just viral hangovers from a cold, and they take two to three weeks to clear up—antibiotics or not. I know that's not what you want to hear when your face feels like it's stuffed with cotton wool, but it's the reality.
There's a massive gap between what people expect and what the evidence supports. A sinus infection is genuinely miserable: the facial pressure, the bunged-up nose, the disturbed sleep, the brain fog. It feels like it needs a heavy hitter. But the misery comes from inflammation blocking those tiny drainage channels. An antibiotic does absolutely nothing to tackle inflammation. It's like trying to unblock a drain by shouting at it.
10 days
The minimum wait before we even consider a script
2–3 wks
Normal duration for acute sinusitis
14 days
What a steroid spray course looks like
The 10-day rule—what it means for you
Let's talk about NICE's famous 10-day rule. It's there for a reason, and understanding why makes the waiting game slightly less infuriating.
Acute sinusitis follows a pretty predictable arc. It usually crashes in a few days after a cold starts, peaks over the next week, and then slowly fades. Being at day five and feeling terrible isn't a sign you need antibiotics—it's just Tuesday for a sinus infection.
The things that do change the picture are:
- Hitting 10 days with zero improvement – not just 'still uncomfortable', but genuinely no upward trajectory.
- Double sickening – you start feeling better around day five or six, then suddenly crash and get worse again. That two-stage slide is our biggest clue that bacteria might have joined the party.
If you want to run a self-check, our guide on viral vs bacterial sinusitis walks you through it step by step.
Why antibiotics usually don't help
Two reasons, and they stack up.
First, it's nearly always viral. Rhinoviruses and the rest are the usual suspects. Antibiotics don't touch viruses—it's like trying to fix a flat tyre with a screwdriver.
Second, even when bacteria do get involved, your immune system handles it 9 times out of 10. Studies show antibiotics offer only a tiny benefit for acute sinusitis, and NICE points out that holding off almost never leads to serious complications.
It's the swelling that makes you feel rough, not the germs. That blocked drain feeling is inflammation. That's exactly why a steroid nasal spray (which shrinks the swelling) often works better at day 10 than an antibiotic would.
When we actually prescribe them
There's a real minority who genuinely need them. NICE flags these situations:
- 10 days or more with no improvement – where a back-up or immediate script might be considered
- Systemically very unwell – not just uncomfortable, but properly knocked sideways with high fever
- Signs of a more serious illness
- High risk of complications – immunosuppression, brittle diabetes, or other serious health issues
- Double sickening with a clear, sharp worsening after initial recovery
Suspected complications aren't for a routine script. Swelling around the eye, vision changes, a blinding headache, neck stiffness or confusion means you dial 999 or head to A&E—not a quick online consultation.
Which antibiotics UK doctors use
| Antibiotic | Position | Adult dose | Course |
|---|---|---|---|
| Phenoxymethylpenicillin | First choice | 500mg four times daily | 5 days |
| Doxycycline | Alternative first choice (penicillin allergy) | 200mg day 1, then 100mg once daily | 5 days total |
| Clarithromycin | Alternative first choice | 500mg twice daily | 5 days |
| Erythromycin | Alternative in pregnancy | 250–500mg four times daily, or 500–1000mg twice daily | 5 days |
| Co-amoxiclav | Second line / systemically very unwell | As prescribed | 5 days |
Doxycycline isn't for kids under 12, and we avoid it in pregnancy. If you can't take penicillin, our guide on clarithromycin and doxycycline covers your alternatives. For the penicillin route, see phenoxymethylpenicillin vs amoxicillin.
When an antibiotic is clinically appropriate, Access Doctor can supply phenoxymethylpenicillin, doxycycline and clarithromycin after a proper consultation.
Back-up prescriptions: a holding pattern
If you're hovering around the 10-day mark without a clear improvement, a back-up script is often the smartest middle ground.
1
You get it, but you don't start it
Keep up the self-care and, if prescribed, your steroid spray. The antibiotics sit in the drawer as insurance.
2
Give it a few more days
A surprising number of people improve in that window and never open the box.
3
Start only if things go south
If symptoms worsen significantly or just refuse to shift, fill it and take the full course.
4
Remember the red flags
Eye swelling, vision changes, severe headache or confusion means A&E, not the spare pills.
The steroid spray route (most people need this)
This is the bit that catches most people out, and it's where the real answer usually hides.
For adults and kids over 12 who've hit the 10-day wall, NICE suggests a high-dose nasal corticosteroid for 14 days. It treats the actual problem—the swelling blocking the drain holes—rather than chasing a bacteria that might not even be there.
| Steroid nasal spray | Antibiotic | |
|---|---|---|
| Targets | Inflammation blocking drainage | Bacteria, if present |
| Useful when | Symptoms persist past 10 days | Bacterial infection is likely |
| Works if cause is viral | Yes—inflammation is inflammation | No |
| Course | 14 days | 5 days |
| Onset | Builds over several days | 24–72 hours if bacterial |
| Resistance risk | None | Significant |
Access Doctor supplies mometasone and beclometasone nasal sprays. Our best nasal spray guide breaks down which is right for you.
The green mucus myth—let's bury it
I'm giving this its own section because it's the number one reason we get overwhelmed with worried patients.
Green or yellow snot does not mean you need antibiotics. That colour comes from an enzyme (myeloperoxidase) in your white blood cells. Viral infections recruit those cells just as much as bacterial ones. Mucus thickens and changes colour partway through any cold, then clears up again—all without a single bacterium in sight.
If your clinician doesn't prescribe based on the colour of your snot, that's good medicine, not dismissiveness. We look at the timeline, the trajectory, and how rotten you feel. The colour is a distraction.
The real cost of unnecessary antibiotics
Side effects for zero gain
Nausea, diarrhoea, thrush—you take these on board without any benefit to offset them.
Doxycycline and sunburn
Doxycycline makes your skin fry in the sun. An avoidable hassle if the course was pointless.
Driving resistance
Both for you and for everyone else. Unnecessary scripts are the biggest driver of resistance.
Gut wreckage
Antibiotics nuke your microbiome. It takes weeks to recover.
Delayed real treatment
A week on a useless antibiotic is a week you could have spent on a steroid spray that would actually work.
False penicillin allergies
A rash during an unnecessary course can leave you with a permanent, often inaccurate, allergy label.
How to get treatment in the UK
Oral antibiotics are prescription-only. Full stop. If a site sells them without an assessment, run the other way.
Your legitimate routes are: your GP, a community pharmacy with NHS Pharmacy First, or a regulated online pharmacy prescribing after a clinical review. In every case, a prescriber decides whether you actually need the antibiotic—and often, the honest answer is no.
Need a clinical review today?
Fill out a short consultation and one of our GPhC-registered pharmacist prescribers will assess your timeline and symptoms. They'll recommend the right course—which might be a steroid spray, not pills. Dispensed from our UK pharmacy with next-day delivery.
View Phenoxymethylpenicillin for Sinusitis →Red flags—stop reading and call 999
Call 999 or go to A&E now if you have swelling or redness around an eye, a bulging eye, double or blurry vision, a blinding headache unlike anything you've had, neck stiffness, drowsiness, or confusion. These suggest the infection is heading for your eye socket or brain—rare, but not something to wait out.
For less urgent but still same-day needs—very high fever, rapid deterioration, or a weak immune system—ring your GP or NHS 111.
Frequently Asked Questions
Do you need antibiotics for a sinus infection?
Most people do not. Acute sinusitis is almost always viral, and antibiotics have no effect on viruses. UK guidance in NICE NG79 is explicit that no antibiotic should be offered for symptoms lasting fewer than 10 days, however uncomfortable they are. Even beyond 10 days, a steroid nasal spray is usually the more appropriate next step. Antibiotics are reserved for the minority where bacterial infection is genuinely likely or where someone is systemically very unwell.
What is the 10-day rule for sinusitis antibiotics?
It is the threshold UK guidance uses before antibiotics are even considered. Acute sinusitis typically takes two to three weeks to resolve fully, and the first 10 days are expected to be uncomfortable. Symptoms that are still present at 10 days without any sign of improvement, or that clearly improved and then worsened again, are what shift the balance. Before that point, the working assumption is a viral infection running its normal course.
Which antibiotic is used for a sinus infection in the UK?
Phenoxymethylpenicillin is the first-choice antibiotic for adults, usually 500mg four times a day for 5 days. For people who cannot take penicillin, doxycycline is an alternative first choice at 200mg on day one then 100mg once daily for four further days, though it is not suitable for children under 12. Clarithromycin is the other alternative. Where someone is systemically very unwell or at high risk of complications, co-amoxiclav may be used instead.
Does green mucus mean I need antibiotics for sinusitis?
No. Green or yellow mucus is one of the least useful signs in the whole of primary care. The colour comes from enzymes released by white blood cells fighting the infection, and it appears just as readily with viral infections as bacterial ones. Many people arrive expecting a prescription on the strength of mucus colour alone. What actually guides the decision is how long symptoms have lasted, whether they are improving, and how unwell you feel overall.
What is a back-up antibiotic prescription for sinusitis?
It is a prescription you hold but do not start immediately, using it only if symptoms worsen rapidly or significantly, or fail to improve within the next few days. NICE supports this approach for people whose symptoms have lasted around 10 days or more without improvement. It avoids committing everyone to a course they may not need, while making sure nobody is left without treatment if things do deteriorate.
Can I get antibiotics for sinusitis online in the UK?
Antibiotics are prescription-only medicines and cannot be bought over the counter. You can request them through a regulated online consultation, where a GPhC-registered pharmacist independent prescriber reviews your symptoms, how long they have lasted and your medical history before deciding whether an antibiotic is appropriate. In many cases the honest answer is that a steroid nasal spray or continued self-care would serve you better, and a good prescriber will say so.
What happens if a sinus infection is left untreated?
Most untreated sinus infections resolve on their own within two to three weeks, which is precisely why antibiotics are not routine. Serious complications are rare, and withholding antibiotics rarely leads to them. The complications that do occur, such as infection spreading to the eye socket, present with unmistakable warning signs including swelling around the eye, vision changes, severe headache or confusion, and these need emergency assessment rather than a routine prescription.
Getting the right treatment
Whether you need an antibiotic, a steroid spray, or just a bit more patience, Access Doctor supplies the right option after a short online consultation. Our GPhC-registered pharmacist prescribers review every case. No GP appointment needed—dispensed from our UK pharmacy.
Antibiotic · Rx
Phenoxymethylpenicillin for Sinusitis
UK first-choice antibiotic where bacterial sinus infection is likely.
View product →Antibiotic · Rx
Doxycycline Capsules for Sinusitis
Alternative first choice for adults who cannot take penicillin.
View product →Steroid spray · Rx
Mometasone Nasal Spray for Sinusitis
Reduces the inflammation blocking sinus drainage past day 10.
View product →Steroid spray · Rx
Beclometasone Nasal Spray for Sinusitis
Established steroid nasal spray for persistent sinus symptoms.
View product →References
- National Institute for Health and Care Excellence. Sinusitis (acute): antimicrobial prescribing (NG79). 2017, updated. nice.org.uk
- NICE Clinical Knowledge Summaries. Sinusitis. cks.nice.org.uk
- NHS. Sinusitis (sinus infection). nhs.uk
- Joint Formulary Committee. British National Formulary: phenoxymethylpenicillin. bnf.nice.org.uk
- Joint Formulary Committee. British National Formulary: doxycycline. bnf.nice.org.uk
- NHS England. Pharmacy First service. england.nhs.uk
- UK Health Security Agency. Antimicrobial resistance: ESPAUR report. gov.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.