Acute vs Chronic Sinusitis: How Long It Lasts and What to Do
Why the 12-week mark changes the whole approach, and why repeated antibiotic courses are the wrong answer for chronic sinusitis.
Part of our Sinusitis condition guide.
Key fact: Acute and chronic sinusitis share a name and almost nothing else. Acute sinusitis is an infection that clears in two to three weeks. Chronic sinusitis is a persistent inflammatory condition lasting 12 weeks or more, where antibiotics have very little to offer and long-term anti-inflammatory treatment is the mainstay.
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View Sinusitis Treatments →The sinusitis timeline
Sinusitis is classified almost entirely by duration, and the categories carry real treatment consequences.
| Duration | Classification | What it means |
|---|---|---|
| Under 10 days | Acute, viral | Normal course. Self-care only. No antibiotic, no steroid spray. |
| 10 days to 4 weeks | Acute, not improving | Consider a high-dose steroid nasal spray. Antibiotic only if bacterial infection likely. |
| 4 to 12 weeks | Subacute | Overdue for review. Look for underlying drivers. |
| 12 weeks or more | Chronic rhinosinusitis | A different condition. Long-term anti-inflammatory treatment and investigation. |
| 4+ episodes a year, clear between | Recurrent acute | Something is repeatedly letting infection in. Find and treat it. |
2–3 wks
normal duration of acute sinusitis
12 wks
threshold for chronic rhinosinusitis
4+
episodes a year defines recurrent acute
Acute sinusitis
Acute sinusitis nearly always starts with a bog-standard cold. That cold inflames your nasal lining, the tiny drain holes swell shut, and suddenly your face feels like it's full of concrete. It's miserable, yes—but it's also entirely predictable.
The usual course is rough but follows a pattern. Symptoms build over the first few days, peak in the first week, then slowly fade over the next one to two weeks. Hitting the two-to-three-week mark before you feel totally back to normal is perfectly standard. What matters isn't how bad you feel on any single day, but the direction you're heading. Someone on day eight who feels rubbish but marginally better than day six is following the script. Someone on day 12 who feels exactly as rotten as they did on day four? That's when we start to take a closer look.
The first 10 days are not a treatment failure. NICE guidance is clear: no antibiotics for acute sinusitis under 10 days. If you're in that window, our guides on antibiotics for a sinus infection and how to relieve sinus pressure cover what actually helps.
The subacute middle ground
Between four and 12 weeks, sinusitis is sometimes called subacute. It is not a formal treatment category so much as a warning sign.
Symptoms lasting a month or more have moved well outside the expected course of a viral infection, but have not yet met the chronic definition. This window is the best opportunity to intervene — identifying an untreated allergy, stopping smoking or starting a steroid nasal spray at this stage can prevent the slide into genuinely chronic disease.
If you are in this window, the useful step is a clinical review rather than another round of self-treatment.
Chronic sinusitis
Chronic rhinosinusitis means symptoms present continuously for 12 weeks or more. It is diagnosed on two or more symptoms, at least one of which must be nasal blockage or nasal discharge, plus either facial pain or pressure, or a reduced sense of smell.
How it feels different
- Less acute pain, more constant pressure — a persistent heaviness rather than the sharp facial pain of an acute attack
- Persistent loss of smell — often the most disabling symptom, and the one people find hardest to live with
- Constant nasal blockage that never fully clears
- Post-nasal drip and throat clearing as a dominant complaint
- Fatigue that is out of proportion to how mild the nose symptoms sound
- Reduced quality of life — chronic sinusitis measurably affects sleep, concentration and mood
Chronic sinusitis is generally divided into two types: with nasal polyps and without. The distinction guides treatment, and the polyp form is more strongly associated with asthma and with persistent loss of smell.
Recurrent acute sinusitis
This is a third pattern, distinct from both, and it is frequently mislabelled.
Recurrent acute sinusitis means four or more discrete episodes in a year, with complete resolution between them. That last part is the discriminator. If symptoms never fully clear, it is chronic sinusitis, not recurrence.
Keeping a simple diary of episode dates and how long each lasted is genuinely useful here. It is what a clinician needs to distinguish the two patterns, and recollection alone rarely separates them reliably.
Side-by-side comparison
| Acute sinusitis | Chronic sinusitis | |
|---|---|---|
| Duration | Under 12 weeks, usually 2–3 | 12 weeks or more, continuous |
| Underlying process | Infection | Persistent inflammation |
| Usual trigger | A cold | Ongoing driver: allergy, polyps, irritants |
| Facial pain | Prominent, sometimes severe | Milder, more a constant pressure |
| Fever | Possible | Uncommon |
| Loss of smell | Temporary | Often persistent, sometimes total |
| Antibiotics | Small role, if bacterial | Very limited role |
| Steroid nasal spray | Consider after 10 days, 14-day course | Mainstay, used for months |
| Saline irrigation | Helpful | Core part of treatment |
| Imaging | Not needed | CT sometimes, via ENT |
| Who manages it | Self-care, pharmacist, GP | GP, often with ENT referral |
Why antibiotics fail in chronic sinusitis
This is the single most important practical point on this page, because the pattern is so common: repeated antibiotic courses, brief or no improvement, symptoms returning, another course.
Antibiotics kill bacteria. In chronic sinusitis the problem is not primarily bacteria — it is that the lining of the sinuses has become and stayed inflamed. That swelling narrows the drainage channels, mucus does not clear properly, and the cycle sustains itself. Killing bacteria does not reduce swelling.
People do sometimes feel briefly better on a course, which reinforces the habit. That is usually the natural fluctuation of a chronic condition rather than the antibiotic working, and it comes at the cost of side effects and resistance each time.
If you have had several antibiotic courses for sinus symptoms in the past year with no lasting benefit, that itself is diagnostic information. It points towards chronic inflammatory disease and should prompt a change of approach rather than another prescription.
How chronic sinusitis is actually treated
1
Steroid nasal spray, used long term
The mainstay. Reduces the inflammation narrowing the drainage channels. Used consistently over months, not as a short course, and not only when symptoms flare. Access Doctor supplies mometasone nasal spray and beclometasone nasal spray.
2
Saline nasal irrigation, daily
Larger-volume rinsing rather than a light spray. Clears mucus, allergens and inflammatory debris, and improves how well the steroid spray reaches the lining. Use cooled boiled or distilled water, never straight from the tap.
3
Treat the underlying driver
Allergic rhinitis, smoking, reflux or occupational irritants. Without this, the inflammation keeps being re-provoked no matter how good the spray technique.
4
Give it three months before judging
Chronic sinusitis treatment works slowly. Three months of consistent use is the usual trial period before deciding it has not worked.
5
ENT referral if it persists
For nasendoscopy, CT imaging and consideration of surgery in the minority who need it.
Technique matters more than people expect. A steroid nasal spray aimed straight up the nostril hits the septum and does little. Aim it slightly outwards, towards the same-side ear, and do not sniff hard afterwards — sniffing sends it down the throat rather than leaving it on the lining. Our mometasone nasal spray guide covers technique step by step.
Finding the underlying driver
Allergic rhinitis
The commonest driver. Seasonal or year-round allergy keeps the lining swollen. Often the highest-yield thing to treat.
Nasal polyps
Physically obstruct drainage. Suspect with persistent blockage and long-standing loss of smell. Needs examination.
Smoking and vaping
Direct, continuous chemical irritation. Chronic sinusitis rarely settles while this continues.
Deviated septum
Narrows one side. Suspect with consistently one-sided symptoms.
Asthma
Frequently coexists, particularly with polyps. The airway behaves as one system.
Dental infection
An upper tooth root infection can drive persistent one-sided maxillary sinusitis.
If your sinus problems follow a seasonal pattern or come with sneezing and itchy eyes, the allergy is the thing to treat — see our hay fever and allergic rhinitis guide.
When ENT referral is appropriate
- Symptoms persisting despite three months of proper medical treatment
- Suspected nasal polyps
- Consistently one-sided symptoms, which always warrant examination
- Recurrent acute episodes with an unclear cause
- Complete loss of smell that is not recovering
- Any red flag features
ENT can perform nasendoscopy, a thin camera examination of the nose, and arrange CT imaging. Neither is available in primary care, and both change what can be diagnosed. Functional endoscopic sinus surgery is considered only for people who have not responded to good medical treatment.
Order a Steroid Nasal Spray for Persistent Sinus Symptoms
Where sinus symptoms have lasted beyond 10 days, a steroid nasal spray targets the inflammation blocking drainage. Complete a short online consultation and a GPhC-registered pharmacist independent prescriber will assess whether it suits you, with discreet UK delivery.
View Mometasone Nasal Spray →Red flags at any stage
Call 999 or go to A&E for swelling or redness around an eye, a bulging eye, double or reduced vision, a severe headache unlike your usual headaches, neck stiffness, drowsiness or confusion. These suggest infection spreading beyond the sinuses and need emergency assessment regardless of how long symptoms have been present.
Arrange prompt GP review for consistently one-sided symptoms, blood-stained discharge, or any new neurological symptom.
Frequently Asked Questions
How long does acute sinusitis last?
Acute sinusitis typically lasts two to three weeks and resolves without antibiotics. Symptoms usually peak in the first week then improve gradually. Feeling unwell at day five or day eight is the normal course of the illness rather than a sign that something has gone wrong. UK guidance treats 10 days without any improvement as the point at which the picture changes and further treatment is considered.
What counts as chronic sinusitis?
Chronic sinusitis, properly called chronic rhinosinusitis, means symptoms persisting continuously for 12 weeks or more. The 12-week threshold is the formal dividing line used in UK and European guidance. It is defined by two or more symptoms, one of which must be either nasal blockage or nasal discharge, alongside facial pain or pressure or a reduced sense of smell. It is a persistent inflammatory condition rather than an ongoing infection.
Why do antibiotics not work for chronic sinusitis?
Because chronic sinusitis is driven by persistent inflammation of the sinus lining rather than an active bacterial infection. Antibiotics target bacteria, so they have little to offer when the underlying problem is swelling that blocks drainage. This is why people with chronic sinusitis often describe repeated antibiotic courses that helped briefly or not at all. The mainstay of treatment is a long-term steroid nasal spray combined with saline irrigation, plus finding and treating whatever is driving the inflammation.
What is recurrent acute sinusitis?
Recurrent acute sinusitis means four or more separate episodes of acute sinusitis in a year, with complete resolution of symptoms between each one. It is different from chronic sinusitis, where symptoms never fully clear. The distinction matters because recurrent episodes suggest something is repeatedly allowing infection to take hold, such as untreated allergy, a structural narrowing or nasal polyps, and that underlying factor is what needs addressing.
How is chronic sinusitis treated in the UK?
The mainstay is a steroid nasal spray used consistently over months rather than days, combined with regular saline nasal irrigation. Both work on the inflammation and the impaired drainage rather than on infection. Alongside this, a clinician will look for underlying drivers such as allergic rhinitis, nasal polyps, smoking or a deviated septum. Where symptoms persist despite good medical treatment, referral to an ENT specialist is appropriate, and surgery is considered for a minority.
Can acute sinusitis turn into chronic sinusitis?
It can, though most acute episodes resolve completely. The transition is more likely where there is an ongoing driver keeping the lining inflamed, such as untreated allergic rhinitis, continued smoking, nasal polyps or a structural narrowing. Repeated acute episodes that never fully clear between them can gradually become continuous. This is the main practical reason to treat recurrent sinusitis properly rather than managing each episode in isolation.
When should chronic sinusitis be referred to ENT?
Referral is usually considered where symptoms persist despite three months of appropriate medical treatment with a steroid nasal spray and saline irrigation, where nasal polyps are suspected, where symptoms are one-sided, or where there are red flag features. An ENT specialist can examine the nose with a nasendoscope and arrange a CT scan, neither of which is available in primary care. Surgery is reserved for people who do not respond to medical treatment.
Completing the treatment
Whether your sinusitis is a two-week acute episode or a three-month chronic problem, Access Doctor supplies the appropriate option after a short online consultation reviewed by a GPhC-registered pharmacist independent prescriber. No GP appointment is needed and orders are dispensed from our UK pharmacy. See the full range on the sinusitis treatment page.
Steroid spray · Rx
Mometasone Nasal Spray for Sinusitis
Mainstay treatment for persistent and chronic sinus inflammation.
View product →Steroid spray · Rx
Beclometasone Nasal Spray for Sinusitis
Established alternative steroid nasal spray.
View product →Antibiotic · Rx
Phenoxymethylpenicillin for Sinusitis
For acute episodes where bacterial infection is likely.
View product →Antibiotic · Rx
Doxycycline Capsules for Sinusitis
Alternative where penicillin cannot be used.
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
- NHS. Nasal polyps. nhs.uk
- Joint Formulary Committee. British National Formulary: mometasone furoate (nasal). bnf.nice.org.uk
- ENT UK. Chronic rhinosinusitis patient information. entuk.org
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.