What does this mean?
An infection that starts in a tooth or the gum is confined at first to the root tip or to the area under the gum. If that boundary does not hold, the inflammation passes from the bone into the soft tissue and moves towards the spaces under the jaw, at the side of the neck and under the tongue. Fever is the finding that, at exactly this point, says the infection is no longer local.
The next thing that tells them apart is the swelling itself. A lymph node reacting to an infection feels like a round lump the size of a hazelnut, with edges you can make out with your fingers and which moves under the skin. In a spreading infection the edge of the swelling is unclear: the skin is tight, hot and red, it hurts when touched, and it blurs the jawline as it spreads towards the face. These two are not the same thing, and when the second one appears together with a fever it is not something to wait on.
What decides the risk is where the swelling sits. Swelling that takes in both sides under the jaw at once, feels board-hard to the touch and pushes the tongue upwards suggests that the floor of the mouth is involved; the real danger there is not the pain but the narrowing of the airway. Swelling that climbs towards the area around the eye follows a different path. In both situations, waiting at home on antibiotics taken by mouth is not counted as a suitable option.
Behind neck swelling that comes with a fever there is usually a source inside the mouth; causes arising from a salivary gland or from the throat can give a similar picture too. The following are the possibilities that are commonly considered, and it is the examination and the imaging that tell them apart.
Likely causes
What helps at home?
- Do not put heat on the swollen area and do not try to press it, drain it or burst it; heat and pressure may make it easier for the inflammation to spread over a wider area.
- Do not start leftover antibiotics, or antibiotics prescribed for someone else, on your own decision; they may partly suppress the signs, delay you seeking care and make the later assessment harder.
- Take your temperature and write down the time, and follow the edge of the swelling through the day. How quickly the swelling has grown is more valuable to the clinician than how severe the pain is.
- When you go in, take a list of the medicines you use and your most recent dental X-ray if you have one; which tooth the source is decides the direction of treatment.
- If you have trouble swallowing, cannot swallow your own saliva or are drooling
- If you are struggling to breathe, or your voice has become muffled and changed when you speak
- If you cannot open your mouth two fingers wide
- If the swelling has taken in the area under the tongue, or both sides of the jaw at once, and your tongue is being pushed upwards
- If your fever has risen and shivering has started, or the swelling is visibly growing within hours
Frequently asked questions
- If I start antibiotics, will the swelling go away?
- In an infection that has spread, antibiotics alone are not enough. The pus has to be drained and the source, meaning the tooth involved, has to be dealt with; as long as the source is still there, medication most of the time only slows the picture down. Which antibiotic is given, by which route and for how long is decided after the examination and, where needed, imaging.
- My tooth does not hurt at all; can a tooth still be the source?
- It can. In a tooth whose nerve has died the sense of pain is lost; when the infection moves on quietly and reaches outside the bone, the first thing noticed is swelling rather than pain. So the absence of pain does not rule out a dental source. At the examination it is not only the tooth you suspect that is looked at: all the teeth and the X-ray are assessed together.
- Should I go to a dentist or to the emergency department?
- When a fever goes together with neck swelling, the first address is the emergency department; that is where the safety of your breathing and swallowing is assessed and where treatment through a vein is given. Treatment of the dental source is planned once this first stage has been made safe. If there is difficulty swallowing, shortness of breath or an inability to open the mouth, call 112 before setting off.
This content is for general information and does not replace an in-person examination. Symptoms overlap between conditions, and a diagnosis can only be made clinically.