Teething or Illness?

When to get help

The rule that settles most 2am arguments: a temperature of 38°C (100.4°F) or more is not teething. The NHS lists a slightly raised temperature among teething symptoms and specifies less than 38°C. Anything at or above that is a fever, and the fever thresholds apply.

Seek urgent advice — NHS 111 in the UK (call rather than use the website for a child under 5), the GP out-of-hours service in Ireland, your paediatrician in the US or Canada, healthdirect on 1800 022 222 in Australia, Healthline on 0800 611 116 in New Zealand — if your baby is under 3 months with a temperature of 38°C (100.4°F) or higher, is 3 to 6 months with 39°C (102.2°F) or higher, has a fever lasting 5 days or more, is refusing feeds, has fewer wet nappies than usual, or is not their usual self and you are worried.

Call emergency services — 999 in the UK, 112 or 999 in Ireland and the EU, 911 in the US and Canada, 000 in Australia, 111 in New Zealand — for a rash that does not fade under a pressed glass, a stiff neck, a bulging soft spot, difficulty breathing, a first seizure, blue, grey or mottled skin, or a baby who is drowsy and hard to wake.

The NHS puts it plainly on its own teething page: you know your baby best, and you should get medical advice if they have any symptoms causing you concern.

What teething actually causes

The NHS list is short, and short is the point:

• a sore, red gum where the tooth is coming through;
• a temperature that is slightly raised but less than 38°C (100.4°F);
• one flushed cheek;
• a rash on the face;
• rubbing an ear;
• dribbling more than usual;
• gnawing and chewing on things a lot;
• being more fretful than usual;
• not sleeping very well.

It also notes that teeth sometimes emerge with no pain or discomfort at all, or with only mild symptoms lasting a few days. Most babies start teething at around six months, though before four months and after twelve months are both normal.

What teething does not cause

The NHS addresses the biggest one directly: some people think teething causes symptoms such as diarrhoea, but there is no evidence to support this. Add to that list, because none of them appear in any teething guidance:

• a temperature of 38°C (100.4°F) or more;
• vomiting;
• a rash anywhere other than the face, and never a non-blanching one;
• a cough, wheeze or fast breathing;
• refusing all feeds;
• floppiness, drowsiness or being hard to rouse;
• a bulging fontanelle or a stiff neck.

These are the symptoms of an illness that happens to be occurring while a tooth is also coming through — which is statistically likely, because babies teethe for around two years.

The overlaps that cause the confusion

Three teething signs are shared with real illnesses, which is why the argument keeps happening.

Ear rubbing

The NHS lists ear rubbing under teething, and also lists rubbing or pulling an ear under ear infections in babies. The American Academy of Pediatrics notes that many babies pull at their ears to self-soothe or simply to play. On its own it means little. Paired with a fever, poor feeding, ear discharge or a baby who does not react to sounds, it means see a GP — and for babies under 12 months, the NHS routes ear infections to a GP rather than a pharmacist.

One flushed cheek and a facial rash

Both are on the teething list. Both also appear in viral illnesses. The test is what else is happening: teething flush comes without a preceding few days of feeling unwell, and does not spread to the body.

Poor sleep and fretfulness

Universal, and caused by almost everything. The useful question is not why your baby is unsettled but whether they are feeding, breathing normally and rousable.

The trap with the thermometer

Attributing a fever to teething is not just wrong, it is the mechanism by which serious illness gets missed in babies. NICE tells clinicians that a baby under three months at 38°C (100.4°F) or above is high risk, and that a baby aged three to six months at 39°C (102.2°F) or above is at least intermediate risk. Neither recommendation has a teething exemption.

NICE also warns not to rely on whether a temperature falls after medicine to tell serious from non-serious illness, so a baby who settles after paracetamol has not thereby been diagnosed with teething.

Why the confusion is built in

The timing does most of the damage. The NHS's rough guide has central incisors arriving around six months, lateral incisors around eight months, first molars around twelve months, canines around eighteen months and second molars around twenty-four months, with most children having all their milk teeth by two to three years. That is a two-and-a-half-year window during which a tooth is nearly always on the way.

It overlaps almost exactly with the period in which babies lose the antibodies they received before birth and start meeting viruses for the first time, often as childcare begins. So teething and infection are simultaneous for most of the first two years, and coincidence looks like causation. The useful move is to stop asking which one it is and instead check the specific list above.

When teething is genuinely the answer

When your baby is chewing everything, dribbling, has a visibly sore gum with a tooth beneath it, is more clingy than usual, sleeping badly, and otherwise feeding, playing and behaving normally. That picture, without a fever at or above 38°C (100.4°F) and without any of the red flags above, is teething, and the AAP describes much the same pattern of drooling, chewing and mild fussiness.

The practical response is comfort rather than investigation: something firm and cool to chew, extra holding, and if your baby is genuinely distressed, pain relief suitable for their age — check the label or ask a pharmacist. What is not appropriate is deciding a fever is teething and going back to bed.