Postnasal drip: why mucus runs down the throat, and when it comes from a tooth

The lining of the nose and sinuses produces mucus all the time, and this mucus normally runs down into the throat and is swallowed without being noticed. Cleveland Clinic writes that the glands in the nose and throat produce about 1 to 2 litres of mucus a day, and that postnasal drip is felt when more mucus than normal collects and runs down the back of the throat. The NHS describes this picture as mucus in the nose and sinuses and phlegm building up in the throat, and lists its symptoms as a constantly blocked or runny nose, the feeling of a lump or something stuck in the throat, frequent swallowing or coughing to clear the throat, the feeling of mucus slowly running down the throat, and crackling in the ears.

According to the NHS, these symptoms usually last a few days, sometimes longer. Phlegm and mucus are not harmful; they are the body's way of clearing infection. What increases the mucus is the lining of the nose, sinuses and throat swelling and producing more mucus than normal. The causes the NHS lists are infections such as colds, flu and sinusitis, air pollution and cigarette smoke, allergic reactions to pollen, dust and animals, and conditions affecting the nose such as nasal polyps. Cleveland Clinic adds a deviated septum, cold and dry air, spicy foods, pregnancy and hormonal changes, the contraceptive pill and blood pressure medicines, and stomach reflux.

Allergic and non-allergic inflammation of the nose are among the common sources of long-lasting postnasal drip. The NHS writes that allergic rhinitis causes sneezing, an itchy nose, a runny or blocked nose, itchy and watery eyes, a cough and an itchy roof of the mouth, and that symptoms start minutes after contact with the allergen. In non-allergic rhinitis, the symptoms are similar, but the triggers are changes in the weather, exercise, smoke, the smell of perfume and paint, alcohol and spicy foods, pregnancy or hormone medicines, an underactive thyroid gland and some medicines. Among the medicines the NHS lists are blood pressure medicines called ACE inhibitors, beta blockers, painkillers such as aspirin and ibuprofen, and decongestant sprays used for longer than the time on the pack.

Decongestant sprays deserve a special warning, because this is the typical mistake that makes postnasal drip last longer. The NHS writes that decongestant sprays sold without a prescription should not be used for more than 5 days, and that using them for longer can make a blocked nose worse and make it harder for the symptoms to improve. In other words, using the spray more often as the blockage gets worse can turn into a cycle that feeds the blockage the spray itself creates. If you have gone past the time on the pack, ask your pharmacist or your GP (family doctor).

The reflux side is often overlooked. Cleveland Clinic defines reflux that rises as far as the voice box and throat (laryngopharyngeal reflux) as a particular type of reflux in which stomach contents do not stop in the oesophagus but reach the throat. Its symptoms include hoarseness, the feeling of a lump or something stuck in the throat, throat clearing, a long-lasting cough and the feeling of postnasal drip. The important detail is this: with this reflux, typical reflux symptoms such as heartburn and indigestion may be absent. That is why reflux is also considered in someone with no nasal symptoms who keeps needing to clear their throat and whose voice is hoarse in the mornings.

The dental side is rarer, but when it is missed the treatment does not work. The roots of the upper premolars and molars are very close to the floor of the sinus; inflammation at the root tip of one of these teeth, advanced gum disease or an opening left after an extraction can carry infection into the sinus. This is called sinusitis of dental origin (odontogenic sinusitis). When 131 patients in the US with one-sided filling of the upper jaw sinus on CT were followed up prospectively, the cause turned out to be sinusitis of dental origin in 65 of them. The findings that set the dental origin apart were a bad smell, a feeling of facial pressure on the same side, pus on nasal endoscopy and involvement of the frontal sinus on CT as well. Posterior drip was also among the symptoms asked about, but it was not one of these four distinguishing findings. In other words, postnasal drip on its own does not point to a tooth; in a one-sided sinus disease, however, a bad smell and facial pressure on the same side raise the suspicion of a dental source.

An international expert consensus report writes that the diagnosis of sinusitis of dental origin usually needs two clinicians: the ENT doctor confirms the sinusitis with nasal endoscopy, and the dentist confirms the dental problem in the upper jaw with an examination and dental imaging. The report stresses that both sides should suspect this possibility with certain clinical signs and refer the patient to the other clinician. In practice, this means that with sinusitis that is one-sided and does not clear up despite treatment, treatment should not be considered complete until the upper teeth have been imaged.

The last possibility, rare but not to be missed, is tumours of the nose and sinuses. The NHS writes that in the early stages these tumours can cause a blocked nose on one side that does not go away, nosebleeds, a reduced sense of smell and mucus running from the nose or down the throat, sometimes bloody, and that as they progress they can add double vision, a watering eye, pain and numbness in the face that do not go away, and loose teeth. The NHS states that these symptoms can also be caused by much more common conditions, but that they should be checked if they do not improve in a few weeks or get worse.

The first list is signs that point to the common causes of postnasal drip, usually managed at home or with the pharmacy. If an item in the second list applies to you, see a doctor.

In most people, the diagnosis is made with a few questions; imaging and endoscopy are for long-lasting or one-sided pictures.

1. 1

   First, emergency signs

   If there is swelling around the eye, pain when moving the eye, a change in vision, shortness of breath or coughing up blood, the assessment is done the same day, in A&E if needed.

2. 2

   You are asked about duration, side and colour

   How long the discharge has been going on, whether it started after a cold, whether it is on one side or both, its colour, its smell and whether it contains blood narrow down the cause considerably. At home, closing one nostril and breathing out through the other helps you tell whether the blockage and the smell are on one side.

3. 3

   List of medicines and habits

   You are asked how long you have been using blood pressure medicines, hormone medicines, painkillers and decongestant sprays. The NHS writes that the doctor can change a medicine they think is causing the symptoms. You are also asked about smoking and alcohol.

4. 4

   Nose and throat examination

   The NHS writes that the doctor may want to rule out other causes such as nasal polyps. If needed, the ENT doctor looks inside the nose with a thin camera (endoscopy); according to the consensus report, in sinusitis of dental origin pus and swelling are seen at this examination in the channel through which the sinus drains. If hoarseness is to the fore, the voice box is also examined.

5. 5

   Assessing the upper teeth

   With sinusitis that is one-sided, foul-smelling or resistant to treatment, the dentist examines the upper premolars and molars on the same side and uses an X-ray or a 3D scan to look at the root tips, old root canal treatments and extraction sites.

6. 6

   Treatment and follow-up depending on the cause

   Treatment starts according to whether the source is allergy, rhinitis, reflux or a tooth. The NHS writes that with sinusitis that continues despite 3 months of treatment or causes symptoms on only one side of the face, you can be referred to an ENT specialist.

There is no single medicine for postnasal drip; treatment is chosen according to the cause that started it.

Below are decisions that make the drip last longer or lead to the real cause being found late.

The length varies with the cause. The sequence below is the usual course described by the NHS; the plan of the doctor who follows you up comes first.

1. The first days

   According to the NHS, postnasal drip after a cold or flu usually lasts a few days. Plenty of fluids, steam and salt water rinses bring relief during this period.

2. The first 3 weeks

   According to the NHS, a cough usually clears up on its own within 3 to 4 weeks. With sinusitis, a picture that has not improved in 3 weeks with self-care should be taken to a doctor.

3. After a few weeks

   The NHS asks you to see a doctor with postnasal drip that lasts more than a few weeks. At this point, allergy, rhinitis, reflux, polyps and a dental source are reviewed systematically.

4. Sinusitis lasting more than three months

   The NHS writes that with sinusitis that continues despite 3 months of treatment, you can be referred to an ENT specialist. If it is one-sided, imaging of the upper teeth should also be part of this stage.

We do not give a single figure here, because the assessment of postnasal drip usually ends at the pharmacy, but sometimes needs several departments. These are the items that determine the scope:

How clear the cause is

Drip after a cold is managed at home and with the pharmacy, while long-lasting pictures need an examination.

Endoscopy and imaging

With long-lasting or one-sided pictures, nasal endoscopy and a sinus or dental CT scan may be needed.

A dental source

If the source is an upper tooth, root canal treatment, retreatment or extraction, and then replacing the missing tooth, widen the scope.

Need for surgery

With polyps, a deviated septum or chronic sinusitis, an operation may come up.