Sinus and Nose

A bad smell from the nose: is it the sinuses, a tooth or something else?

The first question is who can smell it: only you, or the people around you too?

There is a rotten, foul or pus-like smell in your nose; sometimes it comes with a discharge, sometimes it appears for no reason at all. Behind this complaint there may be ordinary sinusitis, an upper back tooth whose root reaches the floor of the sinus, a bead a child has pushed up their nose, or simply a change in your sense of smell with nothing wrong in the nose at all. Below you will find simple questions that narrow down the source of the smell, the signs that suggest sinusitis of dental origin, and when you should go without waiting for an appointment.

Short answer

A bad smell from the nose most often comes from a sinus infection; if the smell is on one side and comes with a pus-like discharge, the source is often one of the upper back teeth on the same side. In that case an ENT specialist should assess the sinus and a dentist the teeth. In a child, a foul-smelling discharge from one nostril suggests something stuck up the nose. A smell that comes and goes, with no discharge, that only you can notice may be a change in your sense of smell. If the eyelid is red and swollen and moving the eye hurts, the eye looks pushed forward, or there is double vision or reduced vision, go to A&E without waiting.

The commonest cause: A sinus infection, often of dental origin if it is on one side
The questions to ask at home: Who can smell it, is there a discharge, which side
The first thing to consider in a child: Something stuck up the nose
Urgent signs: Painful eye movement with swelling around the eye, double vision, loss of sight

Four questions that narrow down the source of the smell

A bad smell from the nose is not the name of a disease but a symptom. To tell it apart from bad breath coming from the mouth, you can try a simple test: close your lips, breathe out through your nose alone into the palm of your hand and smell it; then do the same through your mouth. If the smell is noticeable only in the breath from your nose, the source is most likely in the nose or sinuses. Next, close one nostril with your finger and breathe out through the other, then swap sides. If the smell stands out on one side, that is valuable information for the clinician.

The second question is the colour and side of the discharge. The NHS lists among the main symptoms of sinusitis pain and tenderness around the cheeks, eyes and forehead, a blocked or runny nose, a reduced sense of smell, green or yellow mucus and a high temperature; bad breath and toothache are among the other symptoms. Sinusitis that follows a cold or flu often clears up on its own within 4 weeks. The critical detail here is in the NHS's own referral criteria: symptoms on only one side of the face are one of the reasons for referral to an ENT specialist.

With one-sided sinus disease, a dental source is far more common than people assume. In the United States, when 131 patients whose sinus CT scan showed opacification of the maxillary sinus on one side were followed prospectively, the cause in 65 of them (roughly half) turned out to be sinusitis of dental origin (odontogenic sinusitis). In the same study, four findings independently pointed to odontogenic sinusitis: pus seen in the drainage channel of the sinus on nasal endoscopy, a foul smell, a feeling of facial pressure on the same side, and involvement of the frontal sinus as well on the CT scan.

The microbes explain why the smell is so noticeable. In a study in Japan of 87 patients operated on for one-sided sinusitis, bacteria that live without oxygen (anaerobes) stood out in the cases of dental origin; those cultured most often were Peptostreptococcus, Prevotella, the Streptococcus anginosus group and Fusobacterium species. These are mouth bacteria that are also found in infections of the tooth root and the gums. The authors report that a foul smell and facial pain often accompany odontogenic sinusitis too.

Reviews of odontogenic sinusitis list the sources as follows: infection at the root tip of the upper premolars and molars, advanced gum disease, filling material spilling into the sinus after root canal treatment, an opening left between the mouth and the sinus after an extraction, a root fragment or implant that has slipped into the sinus, and complications of sinus floor elevation (sinus lift) surgery. A systematic review covering 4,411 sinus lift procedures in 74 studies counts tearing of the sinus membrane and sinusitis among the main complications needing intervention with the method done through a window opened in the side wall; with the method done through the bone, it states that these two are seen less often.

Recent data from Turkey makes the picture clearer. When the CT and MRI images of 107 patients who had endoscopic sinus surgery in Istanbul for one-sided chronic sinusitis that had not responded to medication were examined, 67 patients (63%) showed a dark area on the images that could suggest infection at the tip of a tooth root; yet only 25 of the patients (23%) remembered any disease or procedure involving a tooth in that area. The authors recommend a thorough dental examination and imaging before surgery for these patients. In short, having no dental history does not clear your teeth.

In children the picture is different. In a study in Pakistan of 155 patients found to have a foreign body in the nose, more than half were under 4 years old; the objects found most often were seeds (40%) and plastic beads. The authors write that the history is not always clear, and that the child is often brought in with a one-sided, foul-smelling discharge and a blocked nose. If a foul-smelling discharge has been coming from one of your child's nostrils for weeks and is not responding to treatment for a cold, this is the first thing to consider.

The last possibility is smelling something when there is nothing wrong in the nose. In listing smell disorders, the NHS gives smelling things that are not there, such as smoke or burnt toast (phantosmia), and things smelling different from how they should, often unpleasant (parosmia), as separate headings; the commonest causes are colds, flu, COVID-19, sinusitis, allergies and nasal polyps. Cleveland Clinic writes that phantosmia can be in one or both nostrils, that the smell can be pleasant or foul, intermittent or constant, and that dental problems are among the causes. The telling sign here is that the people around you cannot smell it and there is no discharge.

A rare cause that should not be missed is a tumour of the nose and sinuses. The NHS writes that in the early stages these tumours cause a blocked nose on one side that does not go away, nosebleeds, a reduced sense of smell and sometimes a bloody discharge, and as they progress they can add double vision, watery eyes, persistent pain and numbness in the face, difficulty opening the mouth and loose teeth. These symptoms can also arise from far commoner causes; if a bad smell comes with a bloody discharge and numbness in the face, the examination should not be put off.

Which smell can wait, and which needs an examination

The first list covers pictures that are expected to pass on their own. If even one item from the second list applies, do not wait.

When it fits

If it came after a cold, with a discharge on both sidesThe NHS writes that sinusitis usually clears up on its own within 4 weeks. Rinsing the nose with salt water, painkillers and rest are the work of this period.
If it is easing within a few daysIf the discharge is clearing and the smell and facial pressure get a little lighter every day, the infection is receding. If there is no improvement after 3 weeks of treating it yourself, the NHS asks you to see a doctor.
If smells started seeming strange after flu or COVID-19The NHS writes that a change in the sense of smell is usually not serious and can get better within weeks or months. Smell training works for some people.
If the smell is only in the breath from your mouthThe source is most likely not the nose but the mouth: the top of the tongue, the gums, decayed teeth or the tonsils. In this case, your first port of call is your dentist.

When it doesn't

If the area around the eye is swelling, the eye is red or you are seeing doubleA sinus infection spreading into the eye socket (orbital cellulitis) is an emergency. MSD Manuals writes that this spread most often comes from the neighbouring sinuses, gives pain on moving the eye, restricted eye movement, the eye being pushed forward and reduced vision as the distinguishing signs, and notes that headache and drowsiness should raise the possibility of meningitis. If swelling of the eyelid comes with any of these signs, go to A&E without waiting for an appointment.
If the smell and pus-like discharge are on one side and have lasted for weeksThe NHS counts one-sided symptoms as a reason for ENT referral. This is the most typical appearance of odontogenic sinusitis.
If you have recently had an extraction, root canal treatment, an implant or a sinus lift on the same sideThese procedures are known causes of odontogenic sinusitis. Tell the clinician who did the procedure and the ENT specialist when it was done.
If there is blood in the discharge, numbness in the face or newly loose teethThe NHS lists these among the symptoms that can be seen with nasal and sinus tumours. Although they are often due to other causes, do not put off the examination.

How the source is found

The international consensus statement says that diagnosing odontogenic sinusitis is a job for two clinicians: the ENT specialist confirms the sinusitis, and the dentist confirms the cause in the tooth.

1
The eye and your general condition first
If there is swelling around the eye, redness of the eye, double vision, reduced vision, a severe headache or confusion, the assessment happens in A&E, not in an outpatient clinic. With this picture, do not wait.
2
The history: who, when, which side?
The clinician asks whether only you can smell it, the colour and side of the discharge, how long it has been going on, what procedures have been done on the teeth on the same side, and how many courses of antibiotics you have had before. With a child, whether they have put something up their nose is also asked.
3
Nasal endoscopy
The ENT specialist looks inside the nose with a thin camera. According to the consensus statement, sinusitis is confirmed mainly by seeing pus, swelling or polyps in the channel through which the maxillary sinus drains (the middle meatus). In a child, a foreign body is also seen during this look and is often removed in the same session.
4
Testing the upper back teeth on the same side
The dentist assesses the upper premolars and molars one by one with a cold test, a percussion test and gum pocket measurements. Because a tooth whose nerve has died may give no pain, the testing is not limited to the tooth the patient points to.
5
The right imaging
A cone beam CT (CBCT) scan shows the relationship between the root tips and the floor of the sinus best. If you already have a sinus CT scan, show it to your dentist too; dental findings can be missed in sinus reports.
6
Both sides deciding together
Once a dental source is confirmed, the order of root canal treatment, redoing the root canal, extraction, removing an object that has slipped into the sinus or endoscopic sinus surgery is planned jointly. If the source is not a tooth, treatment continues on the ENT side.

What is done, depending on the source

There is no single treatment for a bad smell from the nose. What is done depends on where the smell comes from.

Simple sinusitis: nasal rinsing and waiting

The NHS lists rinsing the nose with salt water, painkillers and, if needed, a steroid nasal spray recommended by a pharmacist or doctor. Because sinusitis is mostly caused by a virus, antibiotics are rarely needed.

Odontogenic sinusitis: cutting off the source

Root canal treatment or redoing the root canal for infection at the root tip, extraction for a tooth that cannot be saved, and removal of a root or filling material that has slipped into the sinus. The review writes that when both the tooth and the sinus are dealt with, recovery is expected in 90% to 100% of cases; even so, some patients may still need endoscopic sinus surgery after the dental treatment.

Sinusitis after an implant or a sinus lift

The team that did the procedure and an ENT specialist assess it together. If graft material or an implant has slipped into the sinus, removing it, and if the sinus is blocked, endoscopic intervention, come into the plan.

A foreign body in a child: removal by a clinician

The ENT specialist removes the object with suitable instruments; once it is out, the smell and discharge usually settle within a short time.

Smell disorders: treating the cause and smell training

The NHS writes that if there is underlying sinusitis or polyps, steroid sprays can help, that smell training helps some people, but that some changes can be permanent.

If there are several dental problems in the same mouth

An upper back tooth that keeps infecting the sinus is often not alone; the same mouth also has other decayed, root-filled or missing teeth. If more than one tooth is missing or needs extracting, send us your panoramic X-ray or CBCT scan through the form; the dentist who will carry out the treatment reads it and we reply to you in writing within 24 hours. This is a preliminary assessment; the final decision is made after an examination and a CBCT scan, and the sinus side is dealt with as part of the plan. For a problem with a single tooth, the right address is your own dentist.

Common mistakes with a foul-smelling discharge

The points below are wrong decisions often made with this complaint. We set them out so that you can ask the right questions whichever clinician you see.

Papering over it with antibiotics again and again

The comprehensive review of odontogenic sinusitis writes that when there is a treatable dental problem, antibiotics by mouth usually do not resolve the sinusitis. If the smell comes back on the same side after every course, question the source.

Taking the teeth off the list because none of them hurts

In the series of 107 patients in Istanbul, a root tip finding was present in 63% of patients, but only 23% remembered any history involving a tooth. A painless tooth can be the source too.

Taking a child's one-sided discharge for a cold

In a child, a foul-smelling discharge from one nostril that lasts for weeks suggests a foreign body more than a cold. Trying to get it out at home with tweezers or a cotton bud can push the object further in; take your child to an ENT specialist.

Taking medicine for sinusitis when only you can smell it

If there is no discharge and the people around you cannot smell it, the problem may be in your sense of smell. The NHS asks you to see a doctor about a change in smell that has not got better within a few weeks; unnecessary antibiotics do nothing for this picture.

When the smell goes away

The time depends on the source. The course below shows the commonest patterns; the plan of the clinician following you takes priority.

The first 4 weeks with simple sinusitis
The NHS writes that sinusitis usually clears up within 4 weeks, and that you should see a doctor if there is no improvement after 3 weeks of treating it yourself, or after 7 days of treatment from a pharmacy or doctor.
After the source tooth has been treated
Once the source has been removed, the discharge and smell start to ease. If the sinus has not been able to reopen its own drainage route, an intervention by an ENT specialist may be needed.
If it is still there after 3 months
The NHS counts sinusitis that persists despite 3 months of treatment as a reason for ENT referral. At this point the diagnosis and the source need reviewing.
With a smell disorder
The NHS writes that a change in smell can get better within weeks or months, and can sometimes be permanent. If it has not got better within a few weeks, see a doctor.

Don't wait if

There is swelling around the eye, redness of the eye, double vision or reduced vision. Do not wait for an appointment; go to A&E.
You feel very unwell, or painkillers are not working. In this case the NHS asks for an urgent GP appointment. The same applies if your immune system is weakened, for example if you are having chemotherapy.
The smell and discharge are on one side and have lasted longer than 3 weeks. See an ENT specialist and ask for the teeth on the same side to be assessed as well.
A foul-smelling discharge started on the same side after a dental procedure. Call the clinician who did the procedure; after an implant or a sinus lift, this symptom needs assessing separately.
There is blood in the discharge, numbness in the face or newly loose teeth. See an ENT specialist without delay.

What determines the cost

We do not give a single figure here, because behind a bad smell from the nose there may be sinusitis that clears in a few weeks, a tooth needing root canal treatment or extraction, endoscopic sinus surgery or a foreign body. These are the items that determine the scope:

The source of the smell: The nose, the sinuses, a tooth or the sense of smell are completely different routes and the field of different clinicians.
The need for imaging: Nasal endoscopy is often the first step; a cone beam CT scan is added when a dental source is suspected.
Whether the source tooth can be saved: Root canal treatment, redoing the root canal, root tip surgery and extraction are each a separate scope.
Whether sinus surgery is needed: If the sinus cannot drain on its own or there is a foreign body inside, further intervention is needed on the ENT side.

Frequently asked questions

What causes a bad smell from the nose?

The commonest cause is a sinus infection. With a one-sided, pus-like, foul-smelling discharge, the source is often the upper back teeth on the same side. Something stuck up the nose in a child, a changed sense of smell in an adult and, rarely, tumours of the nose and sinuses are also among the causes.

Can a tooth cause a bad smell in the nose?

It can. The roots of the upper molars and premolars reach the floor of the sinus; infection at the root tip, gum disease, root filling spilling into the sinus, an opening left after an extraction or an implant can infect the sinus. In a study of 131 patients with one-sided sinus opacification, the cause in roughly half was a tooth, and a foul smell was one of the findings that set this group apart.

There is a rotten smell in my nose but nobody else can smell it. Why?

If there is no discharge and the people around you cannot smell it, your sense of smell may have changed. The NHS links smelling things that are not there (phantosmia) and things smelling unpleasant (parosmia) to causes such as colds, flu, COVID-19, sinusitis, allergies and polyps. If it has not gone within a few weeks, see a doctor. If there is a foul-smelling, pus-like discharge, on the other hand, a sinus infection comes to the fore.

A foul-smelling discharge is coming from one side of my child's nose

The first thing to consider is something stuck up the nose. In a series of 155 patients with a foreign body in the nose, more than half were under 4 years old, and seeds and beads were found most often. Do not try to get it out at home; take your child to an ENT specialist.

There is a bad smell from my nose after an implant or a sinus lift

Sinusitis is among the complications of a sinus lift that need intervention. Call the clinician who did the procedure; the state of the graft, the implant and the sinus floor is assessed with a CBCT scan, and an ENT specialist joins in if needed.

I took antibiotics and the smell went, but it came back

A smell that comes back on the same side suggests the source may be in a tooth. The review writes that when there is a treatable dental problem, antibiotics by mouth usually do not resolve the sinusitis. Ask for your upper back teeth on the same side to be tested and for a dental CBCT scan.

Which specialist should I see?

With a one-sided, foul-smelling discharge, an ENT specialist looks at the nose with an endoscope; if there is pus in the sinus, the teeth on the same side need to be assessed by a dentist. The international consensus statement says the diagnosis requires the two clinicians to work together. If the smell is only in the breath from your mouth, your first port of call is the dentist.

When is a bad smell from the nose dangerous?

If the eyelid is swollen and red and moving the eye hurts, the eye looks pushed forward, or there is double vision or reduced vision, go to A&E. If there is blood in the discharge, numbness in the face, newly loose teeth or a one-sided blockage that will not go away, see an ENT specialist without delay.

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