Sinus Infection Symptoms: Is It Bacterial or Viral?
A straightforward way to work out what you're dealing with—and the one thing everyone gets wrong.
Part of our Sinusitis condition guide.
Here's the headline: Two things separate bacterial from viral sinusitis, and neither is how rough you feel on any given day or what colour your snot is. It's all about duration (10 days without improvement) and pattern (getting better, then taking a sharp turn for the worse).
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Right, let's get the frustrating bit out of the way first. The symptoms of a viral sinus infection and a bacterial one are almost identical. That's why you're confused. But while the list looks the same, the timeline tells the real story.
Here's what you're probably dealing with:
- Blocked or congested nose — usually the main event
- Facial pain or pressure over the cheeks, forehead or between the eyes, worse when you bend forward
- Loss of smell — which can be surprisingly upsetting
- Thick nasal discharge, any colour (more on that later)
- Headache, often across the front of your head
- Upper toothache — your back teeth sit right next to your sinuses, so this is normal
- Cough, usually worse at night
- Fever, generally low-grade
- Exhaustion and feeling wiped out
- Ear fullness or pressure
This list won't tell you viral from bacterial. The same symptoms show up in both. The thing that gives it away is the timeline, not the tick-boxes. So don't waste your energy over-analysing this list—move on to the next bit.
The two-question self-check
This is the exact same two-question drill I run through with patients in the clinic. Try it yourself.
1
How many days have you been at this?
Count from when the sinus symptoms started, not when the original cold hit. Under 10 days? That's almost certainly viral. 10 days or more with zero improvement? That's when the balance starts to tip.
2
Which direction are you heading?
Are you slowly getting better? Even if it's glacial, that's the right direction. Or did you improve around day five or six and then crash again? That second one—called double sickening—is the big red flag.
3
How unwell are you overall?
There's a difference between feeling rubbish and feeling properly systemically unwell. If you're shivering with a high fever and severe facial pain, that's a signal to get checked now, regardless of the day count.
| Your answers | Most likely | What to do |
|---|---|---|
| Under 10 days, improving | Viral | Self-care. Stick with saline, steam, and pain relief. |
| Under 10 days but systemically wrecked | Possible bacterial | Get seen now. Don't wait for day 10. |
| 10+ days, no improvement | Uncertain | Get assessed. A steroid spray is often the better answer. |
| Improved, then clearly worse | Bacterial more likely | Get assessed. |
| 12 weeks or more | Chronic, not acute infection | Different problem entirely. See our chronic guide. |
Double sickening explained
This is the single most useful thing to know. Most people have never heard of it, but it's the clue that actually matters.
It works like this. You catch a cold, it settles into your sinuses, and you start to feel better around day five or six. You think you're over the worst. Then, over the next day or two, you crash again. Fever returns, the pain ramps up, and you feel worse than before. That's "double sickening."
The mechanism is simple. The viral infection damages the delicate lining of your sinuses and slows down the little hairs that sweep mucus out. Drainage stalls, mucus pools, and the bacteria that were always there find perfect conditions to multiply. It's not complicated, but it's a very real pattern.
But be careful here. Sinusitis naturally fluctuates. Most people have better mornings and worse evenings. Double sickening is a definite improvement over a day or two, followed by a definite downturn. Daily ups and downs don't count.
Viral vs bacterial: full comparison
| Feature | Viral sinusitis | Bacterial sinusitis | How useful? |
|---|---|---|---|
| Duration | Under 10 days typically | 10+ days without improving | Very useful |
| Course | Steady gradual improvement | Double sickening, or stuck | Very useful |
| Systemically unwell | Uncommon | More likely | Useful |
| Severity of facial pain | Mild to moderate | Often more severe | Moderately useful |
| One-sided symptoms | Less typical | More typical | Moderately useful |
| Fever | Mild or absent | May be higher | Moderately useful |
| Mucus colour | Any colour | Any colour | Not useful |
| Mucus thickness | Varies through illness | Varies through illness | Not useful |
| How bad you feel today | Can be dreadful | Can be mild | Not useful |
The stuff you can safely ignore (stop worrying about the colour)
I know you've been staring at the tissue. Stop it. Here's why these signs are a total waste of your worry:
Green or yellow mucus
This is the big one. The colour comes from an enzyme in your white blood cells. Viral infections recruit those cells too. Your mucus will darken partway through any cold and clear again—no bacteria required.
Thick mucus
Depends on your hydration and the stage of the illness, not the organism causing it.
How bad you feel today
Viral sinusitis can be absolutely miserable. Bacterial can be relatively mild. Your immune response determines the severity, not the germ.
Bad breath
Just stagnant mucus draining down your throat. Happens in both.
Toothache
That's anatomy. Your tooth roots sit against the sinus floor.
"I had this before and needed antibiotics"
Past episodes don't predict this one. Treat the current illness, not your history.
When it is not sinusitis at all
Before you go down the bacterial rabbit hole, let's check you're actually chasing the right problem. Lots of things get mislabelled as sinus infections.
- Migraine — massively common. If you get recurrent headaches with nausea or light sensitivity, and your nose isn't actually blocked, it's probably migraine. See our sinus headache vs migraine guide.
- Allergic rhinitis — sneezing, itchy eyes, clear discharge, and a seasonal pattern point to allergy, not infection. Check our hay fever guide.
- Dental infection — one-sided pain with prominent toothache
- Chronic rhinosinusitis — if this has dragged on for 12 weeks, it's not an acute infection. See acute vs chronic.
- Rebound congestion — from using decongestant sprays for more than a week. Your nose gets more blocked when you stop.
What to do with your answer
If it's viral and you're under 10 days
Self-care isn't a holding pattern—it's the actual treatment. Saline rinses, steam, regular paracetamol or ibuprofen, fluids, and sleeping propped up. Our sinus pressure relief guide has the practical stuff.
If you've hit 10 days with no improvement
This is the point where a steroid nasal spray often does more than an antibiotic. It shrinks the swelling that's blocking the drains, rather than chasing bacteria that might not even be there. UK guidance recommends a high-dose spray for 14 days. Access Doctor supplies mometasone and beclometasone after consultation.
If you've double-sickened or are systemically unwell
This group genuinely might need an antibiotic. Access Doctor can supply phenoxymethylpenicillin, doxycycline, or clarithromycin if appropriate. Our antibiotics guide explains how the decision is made.
Can a test tell you?
Short answer: no, not in routine practice. There's no quick swab or blood test in UK primary care that separates viral from bacterial sinusitis.
Sinus puncture with culture would be definitive, but it's invasive and only used in hospital for severe cases. Imaging doesn't help either—a CT scan shows fluid and inflammation in both viral and bacterial infections, which is why we don't use scans for this. Blood tests like CRP are non-specific.
That's why the clinical rules matter. Duration and pattern are what we have, so that's what the guidance is built on.
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Fill out a short consultation and a GPhC-registered pharmacist prescriber will weigh your timeline and symptoms. They'll recommend a steroid spray, an antibiotic, or continued self-care—with discreet UK delivery.
Start Sinusitis Consultation →Red flags—stop reading and call 999
Call 999 or go to A&E immediately for 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 override every rule on this page—day count doesn't matter.
Contact your GP or NHS 111 today if you have a very high fever, feel dangerously unwell, are deteriorating fast, or have a weakened immune system or poorly controlled diabetes.
Frequently Asked Questions
Is my sinus infection bacterial or viral?
Almost certainly viral if it has lasted fewer than 10 days and is gradually improving. Bacterial infection becomes more likely with one of two patterns: symptoms persisting beyond 10 days with no improvement at all, or a clear course of getting better around day five or six and then distinctly worse again. That second pattern, called double sickening, is the most useful single pointer. Severity on any given day and the colour of your mucus tell you very little.
What is double sickening in a sinus infection?
Double sickening describes a two-stage illness. You catch a cold, develop sinus symptoms, start to improve around day five or six, and then get noticeably worse again with returning fever, increasing facial pain or thicker discharge. The initial viral infection damages the sinus lining and impairs drainage, creating conditions where bacteria can take hold. Clinicians treat this pattern as one of the stronger indicators that a secondary bacterial infection has developed.
What colour is mucus with a bacterial sinus infection?
There is no colour that indicates bacterial infection. Green and yellow mucus occurs in viral infections just as readily, because the colour comes from an enzyme in the white blood cells your immune system sends to any infection. Mucus commonly thickens and darkens midway through an ordinary cold then clears again without any bacteria involved. This is one of the most widely believed and least reliable signs in primary care.
How long does a viral sinus infection last?
A viral sinus infection typically lasts two to three weeks in total, with symptoms peaking during the first week and improving gradually afterwards. Feeling rough at day six or seven is the expected course rather than a sign of bacterial infection. What matters is the direction of travel: someone slowly improving is following the normal pattern, while someone at day 12 who is exactly where they were at day four is not.
Can a doctor tell if a sinus infection is bacterial?
Not with certainty in a routine consultation. There is no quick test in UK primary care that reliably distinguishes bacterial from viral sinusitis. Sinus puncture and culture would be definitive but is invasive and not used routinely, and imaging cannot separate the two either. Clinicians therefore work on duration, pattern and how systemically unwell you are, which is exactly the information you can gather yourself before seeking advice.
Does facial pain on one side mean bacterial sinusitis?
One-sided facial pain raises the suspicion of bacterial infection somewhat, particularly if it is severe, and it also raises the possibility of a dental cause since upper tooth roots sit close to the maxillary sinus. It is a useful signal rather than proof. Persistent one-sided sinus symptoms should always be assessed by a clinician rather than self-managed, because one-sidedness is one of the features that warrants examination.
Should I wait or see someone about my sinus infection?
Wait and self-manage if you are under 10 days and gradually improving, since that is the normal course. Seek assessment if you have passed 10 days with no improvement, if you improved and then clearly worsened, or if you feel systemically very unwell. Seek emergency care immediately, whatever the duration, for swelling or redness around an eye, vision changes, a severe headache unlike your usual ones, neck stiffness or confusion.
Completing the treatment
Whatever your self-check tells you, Access Doctor can supply the right option after a short online consultation with a GPhC-registered pharmacist prescriber. No GP appointment needed—dispensed from our UK pharmacy. Browse the full range on our sinusitis treatment page.
Steroid spray · Rx
Mometasone Nasal Spray for Sinusitis
For symptoms past day 10 that are stuck.
View product →Steroid spray · Rx
Beclometasone Nasal Spray for Sinusitis
Alternative steroid spray for persistent inflammation.
View product →Antibiotic · Rx
Phenoxymethylpenicillin for Sinusitis
UK first-choice antibiotic when the pattern fits.
View product →Antibiotic · Rx
Clarithromycin Tablets for Sinusitis
Alternative for adults who can't take penicillin.
View product →References
- National Institute for Health and Care Excellence. Sinusitis (acute): antimicrobial prescribing (NG79). nice.org.uk
- NICE Clinical Knowledge Summaries. Sinusitis. cks.nice.org.uk
- NHS. Sinusitis (sinus infection). nhs.uk
- European Position Paper on Rhinosinusitis and Nasal Polyps (EPOS). rhinologyjournal.com
- Joint Formulary Committee. British National Formulary: phenoxymethylpenicillin. bnf.nice.org.uk
- NHS. Migraine. nhs.uk
- UK Health Security Agency. Managing common infections: guidance for primary care. 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.