My face is swollen: when can I wait, and when should I go to A&E?

Facial swelling is usually not the start of the story but the middle of it. The StatPearls text reviewing odontogenic infections of the face and neck states that patients typically come in with swelling of the face or neck after one to two weeks of increasing toothache. In other words, the pain has already given its warning long before the swelling appears. Swelling means that pus has got past the bone around the tooth and spilled into the soft tissue.

Which way the pus goes is decided by which side of the bone the tip of the root sits on, and this explains where on the face the swelling appears. Because the root of the upper canine is long, the infection can travel up towards the side of the nose and under the eye. With the upper back teeth, the swelling mostly gathers in the cheek. With the lower back teeth, what decides it is whether the root tips sit above or below what is called the mylohyoid line: above it, the infection passes under the tongue; below it, under the jaw. The same text reports that infections starting in the lower jaw can move on into the deep spaces of the neck and from there as far as the chest cavity.

That is why the direction of the swelling matters more than its size. Painful swelling with clear borders that stays in the cheek is a picture that calls for seeing a dentist the same day. Swelling that is starting to close the eyelid, moving from the edge of the jaw down into the neck, or pushing the floor of the mouth upwards is an entirely different category. There is no threshold you can measure with a ruler; what you look at is where the border has moved to.

On the criteria for an emergency there is a clear list, and it is worth learning by heart. The NHS says that anyone with a dental abscess who is struggling to breathe, speak or swallow, whose eye is swollen or painful or who suddenly has problems with their vision, who has a lot of swelling inside the mouth, or who is having difficulty opening the mouth, should call 112 or go to A&E. The same source adds that you should not drive yourself to A&E, that someone should take you or you should call an ambulance, and that you should take the medicines you are on with you.

The severest form of an infection spreading from the lower back teeth is Ludwig's angina. According to StatPearls, 90% of cases start from the lower second and third molars; the picture involves the spaces under the jaw, under the tongue and beneath the chin together, and it threatens the airway. The same source relates that swelling can develop in the structures of the airway within 30 minutes of the symptoms starting, and that a mortality rate of more than 50% before the antibiotic era stands at around 8% today with airway management and antibiotics. The signs that make the diagnosis are swelling under the jaw on both sides that is as hard as a board, the tongue being pushed up, drooling, a mouth that will not open and a muffled voice.

Antibiotics are a much misunderstood item in this picture. The Cochrane review of acute dental infection in adults reports that an antibiotic added to dental treatment makes little or no difference to pain and swelling, and that the reliability of the evidence is low. The same review stresses that there is no study in which an antibiotic was used on its own without dental treatment, and that unnecessary use contributes to resistance. In a patient with signs of spreading, a high temperature or a suppressed immune system, an antibiotic is the right decision; but an antibiotic prescribed on its own, without cleaning out the source, only buys time.

The logic of a lasting solution is simple: the pus is drained and the source is removed. The NHS likewise writes that a dental abscess does not clear on its own, that its treatment is draining the pus, and that if it comes from a tooth, root canal treatment or extraction may be needed. The swelling going down, or the pain stopping, does not take the place of that step; when the pus finds a way out, the pain eases too, and the infection stays where it is.

The two lists below separate out which door to go to with this complaint. If even one item on the lower list applies to you, do not look at the upper one.

Treating this picture is the job of your own dentist or of A&E. The sequence below shows what to expect from the first assessment through to the lasting decision.

1. 1

   Screening for signs of spreading

   The first thing looked at is not the diagnosis but the danger: breathing, swallowing, speech, how far the mouth opens, the state of the floor of the mouth, temperature and general condition. If any of these is disturbed, the work starts not in the dental chair but at A&E.

2. 2

   Identifying the source

   Which tooth it comes from is worked out with an examination, a vitality test, pocket measurements and an X-ray. Anything done before the source has been found stays temporary.

3. 3

   Draining the pus

   The NHS states that the treatment of a dental abscess is draining the pus. Drainage is carried out from inside the tooth, through a small cut in the gum, or from inside the pocket; as soon as the pressure drops, the throbbing pain stops.

4. 4

   Removing the source

   If the source is inside the tooth, root canal treatment is done; if it is in a gum pocket, the pocket and the root surface are cleaned; if the tooth cannot be saved, it is extracted. When this step is skipped, the swelling comes back.

5. 5

   Using antibiotics where they belong

   If there is a high temperature, a sign of spreading or a patient whose immune system is suppressed, antibiotics come in. The Cochrane review reports that an antibiotic added to dental treatment makes little or no difference to pain and swelling; in other words, antibiotics go alongside the treatment when needed, not in place of it.

6. 6

   A check-up and planning for the gap

   The swelling has to be seen to be going down. If the tooth was extracted, how the gap will be filled is discussed at the same appointment; putting that decision off is not free where the bone in that area is concerned.

Once the acute picture is resolved, the real decision is what happens to the source. The list starts with the least invasive.

The points below are the wrong decisions we come across most often with facial swelling. We are writing them so that you can ask the right questions whichever clinician you see.

The sequence below applies to the route that starts with draining the pus. The timings vary from person to person; the plan of the clinician treating you takes priority.

1. Straight after drainage

   Because the pressure drops, the throbbing pain stops quickly. The swelling in the cheek goes down more slowly; a clear improvement is expected within a few days.

2. The first few days

   The NHS advice applies to this period: eat soft food, stay away from very hot and very cold food and drink, carry on cleaning your teeth with a soft brush, and do not exceed the recommended dose of painkiller. If you were given antibiotics, do not stop them because you feel better.

3. Treating the source

   Drainage brings relief; it does not treat. The picture does not count as closed until root canal treatment, pocket treatment or extraction has been completed.

4. Filling the gap

   If the tooth was extracted, how that area will be filled is a separate decision. If your loss has stayed at one tooth, the route lies with your own dentist; if it has spread to more than one, the plan is built around the whole mouth.

We do not give a single figure here, because the route may end with a drainage or may extend to root canal treatment, extraction and then filling the gap. These are the items that determine the scope:

How severe the picture is

Swelling that stays confined to the cheek and a widespread infection needing hospital assessment are not assessed within the same scope.

Where the source lies

In a picture coming from the tip of the root, the work is root canal treatment; in one coming from a gum pocket, it is cleaning the pocket and the root surface. The lengths and numbers of sessions are different.

Whether the tooth can be saved

Root canal treatment with a crown on top, and extraction with whatever follows it, are costed separately. That decision is given by imaging.

How many teeth are affected

Behind repeated infections there is usually advanced gum disease, and it does not stop at one tooth. A single-tooth plan and a plan covering the whole mouth are not costed the same way.