Sinus infections — when to seek treatment
Reviewed by the My London Pharmacy clinical team, Yvonne Lim, Pharmacist Independent Prescriber
·29 July 2026
·8 min read
Quick answer
Sinusitis is inflammation of the sinuses, often after a cold, causing facial pain, a blocked nose and thick mucus. Most cases are viral and improve within two to three weeks with self-care. When symptoms are severe, persistent or recurring, a clinician can assess whether nasal treatment or, in some cases, antibiotics are appropriate.
What a sinus infection is
The sinuses are small, air-filled spaces set within the bones of the face: behind the cheeks, above and between the eyes, and in the forehead. They are lined with a thin layer of mucus and microscopic hairs called cilia that sweep debris and particles towards the back of the nose, helping to keep the airways moist and clean. When this lining becomes inflamed and swollen, usually after a cold or other viral infection, the narrow channels that let the sinuses drain become blocked. Mucus then builds up, pressure rises, and the result is the familiar heaviness and pain of sinusitis.
Most sinus infections are caused by viruses rather than bacteria, which is why they so often clear on their own without antibiotics. Occasionally a bacterial infection develops on top of a viral one, but this is far less common than many people assume. Doctors describe sinusitis as acute when it lasts up to around four weeks, subacute between four and twelve weeks, and chronic when symptoms persist for twelve weeks or more. Recognising roughly which pattern you are dealing with helps guide how it is managed and when it is worth seeking help, rather than treating every blocked nose as a bacterial infection that needs medication.
How a sinus infection feels
Sinusitis tends to produce a recognisable cluster of symptoms, which commonly includes:
- Pain, tenderness or a sense of pressure around the cheeks, eyes or forehead
- A blocked or runny nose, often with thick, discoloured mucus
- A reduced or altered sense of smell, and sometimes taste
- Pain that feels worse when bending forward or lying down
- Headache, a raised temperature, bad breath, or a cough that can be worse at night
- A general feeling of being run down and tired
Pain across the upper teeth and a feeling of fullness in the face are common, because the affected sinuses sit close to the tooth roots and cheekbones. Discoloured, yellow or green mucus is often taken as proof of a bacterial infection, but on its own it is not: it simply reflects the immune cells at work and is seen in ordinary viral illness too. The most telling clue is the overall pattern and timeline rather than the colour of what you blow out.
Telling sinusitis apart from a cold
A cold and acute sinusitis share a great deal, and in practice sinusitis often begins as a cold. The difference is largely one of location and timing. A cold tends to bring a sore throat, sneezing and a runny nose that peak in the first few days and then steadily ease. Sinusitis is dominated by facial pressure, pain over the sinuses and congestion, and it tends to linger once the other cold symptoms have faded.
One particularly useful pattern is sometimes called double-sickening: a cold appears to be settling after several days, only for the symptoms to worsen again with renewed facial pain and fever. This return of symptoms after an apparent recovery is a classic sign that sinusitis has developed, and occasionally that a secondary bacterial infection has taken hold. Being aware of this pattern helps you judge whether something is simply a slow-clearing cold or a sinus infection that may need a closer look.
Self-care that helps most cases
Because most sinus infections are viral, they usually settle with supportive care that eases symptoms while your body clears the infection. Helpful measures include resting, drinking plenty of fluids, and using pain relief such as paracetamol or ibuprofen if these are suitable for you. Keeping your head slightly raised at night can reduce the pressure that builds when lying flat.
Warm face packs held gently over the cheeks and forehead can soothe pressure, and inhaling steam from a bowl of hot water may offer temporary relief for a stuffy nose. Salt water nasal rinses, available from pharmacies as sachets or ready-made sprays, help clear mucus and are gentle enough to use several times a day; rinsing with clean, previously boiled and cooled water is important if you make up a solution yourself. A short course of a decongestant spray or tablet can relieve a blocked nose, but decongestant sprays should not be used for more than about a week, as longer use can cause rebound congestion that leaves the nose feeling more blocked than before. Giving these measures time matters, because acute sinusitis often takes two to three weeks to resolve fully even when everything is progressing normally.
When treatment is considered
If symptoms are severe from the outset, or have shown no sign of improving after around ten days, a clinician may look more closely and consider treatment aimed at the inflammation. For ongoing congestion and swelling, a steroid nasal spray such as Beconase can help calm the lining of the nose and improve drainage, and it is particularly useful where an allergic component is keeping the nose inflamed. Steroid sprays work gradually over days rather than instantly, so using them consistently and with the correct technique gets the best result.
Where crusting, soreness or recurrent infection inside the nostrils is part of the picture, a clinician might consider an antibiotic or antiseptic nasal preparation such as Naseptin or Bactroban Nasal Ointment (MUPIROCIN), both applied inside the nose. Oral antibiotics are only sometimes needed, because most sinusitis is not bacterial and will not respond to them. In line with NICE and NHS guidance on antibiotic stewardship, they are reserved for cases where a bacterial infection is likely, symptoms are severe, or there are signs of complications, rather than being used as a routine first step. This measured approach protects you from unnecessary side effects and helps keep antibiotics working for everyone.
What makes sinusitis more likely
Some people are more prone to sinus infections than others, and understanding why can help reduce how often they occur. A recent cold or other viral infection is the most common trigger, because swelling in the nose stops the sinuses draining properly. Allergies such as hay fever have a similar effect, keeping the nasal lining inflamed and congested for longer stretches of the year.
Other factors that raise the risk include smoking or regular exposure to smoky or polluted air, which irritates and slows the protective cilia; a deviated nasal septum or other structural differences that narrow the drainage channels; and nasal polyps, which are soft, non-cancerous swellings in the lining of the nose. Dental infections in the upper teeth can occasionally spread to the nearby sinuses as well. Keeping allergies well controlled, avoiding tobacco smoke, and managing congestion promptly during a cold can all help lower how often sinusitis takes hold.
Recurrent and long-lasting sinusitis
Some people experience sinus infections that keep returning, or symptoms that linger for many weeks and blur into one another. Persistent congestion, ongoing facial pressure, a blocked nose or a reduced sense of smell that does not recover all deserve proper review, as they can quietly wear away at sleep, concentration and quality of life. Chronic sinusitis, defined as symptoms lasting twelve weeks or more, is managed differently from a one-off acute infection and often needs a longer-term plan rather than repeated short courses of treatment.
A clinician can look for contributing factors such as allergies, nasal polyps or a structural issue inside the nose, and may suggest regular use of a steroid nasal spray and saline rinses to keep inflammation down. Where symptoms are stubborn or the diagnosis is unclear, referral to an ear, nose and throat specialist for further assessment, imaging or, in some cases, surgery may be appropriate. Managing any underlying allergy well, using nasal sprays correctly, and keeping the nasal passages clear can all reduce how frequently sinusitis flares.
When to seek prompt help
Most sinus infections are not serious, but a small number of symptoms need urgent attention because they can signal that infection has spread beyond the sinuses to the eye, the surrounding bone or, rarely, towards the brain. Seek prompt medical advice, or call 999, if you notice:
- Swelling, redness or pain around one or both eyes
- Vision changes such as double vision or reduced vision
- A severe headache, especially with a stiff neck
- Confusion, drowsiness or a very high temperature
- Swelling of the forehead
These complications are uncommon, but recognising them means you can act quickly if they ever appear. It is also worth seeking non-urgent advice if symptoms are severe, keep coming back, or have not begun to improve after around ten days, so that the far more common, straightforward cases can be managed with the right support and the rare serious ones are picked up early.
Frequently asked questions
Do sinus infections need antibiotics?
Most sinus infections are caused by viruses and clear without antibiotics. A clinician will only consider antibiotics when there are signs a bacterial infection is present or symptoms are severe or prolonged.
How long does sinusitis usually last?
Acute sinusitis often improves within two to three weeks. If symptoms continue beyond this, keep returning, or last twelve weeks or more, it is worth seeking advice.
Can a nasal spray help a sinus infection?
A steroid nasal spray can reduce inflammation and improve drainage, particularly where allergy contributes to congestion. A clinician can advise whether one is suitable for you.
Does green mucus mean I need antibiotics?
Not on its own. Discoloured mucus is common in ordinary viral infections and does not by itself confirm a bacterial infection or the need for antibiotics.
Why do I keep getting sinus infections?
Recurring sinusitis can be linked to allergies, nasal polyps or a structural issue in the nose. A clinician can look for underlying causes and suggest a longer-term plan.
When is a sinus infection an emergency?
Swelling or pain around the eyes, vision changes, a severe headache with a stiff neck, or confusion need urgent care, as they may signal the infection has spread.