Teething vs illness: how to tell the difference
Teething gets blamed for an enormous range of symptoms in babies and toddlers. Fever, diarrhea, vomiting, ear infections, rashes, coughs: you will find teething cited as a possible cause of all of these in parenting forums and, sometimes, in older health advice. The scientific evidence, however, paints a very different picture. Understanding what teething actually does, and what it does not, helps you respond to your baby's symptoms more confidently and ensures you do not dismiss real illness as "just teething."
Why the teething myth matters
The reason it is important to be clear about this is not to be pedantic. It is because mislabelling illness as teething can delay treatment. A baby with a genuine ear infection, a urinary tract infection, or a viral illness needs care. If those symptoms are attributed to teething and watched without action, the window for early intervention can close.
Multiple systematic reviews of teething research confirm the same thing: teething causes local symptoms in and around the mouth, and that is essentially where its effects end. A landmark study published in Pediatrics (Tighe and Roe, 2007) and a larger review by McIntyre and McIntyre (2002) both found that systemic symptoms like high fever, diarrhea, and vomiting were not significantly more common during teething than at other times. The AAP (American Academy of Pediatrics) states clearly that high fever and diarrhea are not normal teething symptoms.
What teething actually does cause
Teething produces symptoms that are local to the mouth and gums. These are well-supported by research and are what you can reasonably expect during the weeks when a tooth is coming through.
- Drooling. Significantly increased saliva production is one of the most consistent teething signs. You may notice your baby's chin and chest becoming red or chapped from constant contact with saliva.
- Gum rubbing and gnawing. Your baby may press their gums together firmly, chew on fingers, toys, or the edge of the cot, and seem to want hard things to bite on. This reflects the pressure and discomfort of the tooth pushing through.
- Mild gum inflammation. The area of gum where the tooth is erupting may look slightly swollen, red, or puffy. You might see or feel a hard lump beneath the gum surface.
- Fussiness. Some increase in irritability is common, particularly in the day or two immediately before a tooth breaks through, when gum pressure is at its highest.
- Slightly disturbed sleep. Gum discomfort can disrupt sleep in some babies. This is not universal: many babies teethe without any noticeable change in their sleep patterns.
- Mild temperature elevation. Some studies have recorded a very modest rise in baseline temperature during active teething, typically remaining below 37.5C. This is not a fever. It does not require treatment with paracetamol.
- Slightly loose stools in some babies. A small number of studies have noted marginally looser stools in some teething babies, possibly because of increased saliva being swallowed. This is not the same as diarrhea, which is frequent, watery stools.
What teething does not cause
This list is just as important as the one above. None of the following are teething symptoms. If your baby has any of these, the cause is something other than teething and it should be investigated accordingly.
- A fever of 38C or above. This is the single most important point. A temperature of 38C or higher is a fever caused by illness, not teething. The fact that a tooth happens to be coming through at the same time is a coincidence, because teething happens continuously for two to three years and overlaps with many normal childhood illnesses. Treat the fever and the potential illness, not the teething.
- Vomiting. Teething does not cause vomiting. If your baby is vomiting, something else is causing it.
- Significant or persistent diarrhea. Watery, frequent stools are not caused by teething. They suggest a gastrointestinal infection or another cause that needs assessment.
- Rashes on the body. A drool rash on the chin and chest is a normal skin response to constant saliva contact. A rash anywhere else on the body is not caused by teething.
- Ear infections. Babies pull at their ears for many reasons including tiredness and general discomfort, but a genuine ear infection is caused by bacteria or a virus, not by teething. If your baby is pulling at an ear AND has a fever or seems unwell, they should be seen by a doctor.
- Upper respiratory symptoms. A runny nose, cough, or congestion is caused by a viral infection, not by a tooth coming through.
- Serious illness. Any baby who seems genuinely unwell, lethargic, unusually difficult to wake, has a high-pitched or unusual cry, has a rash that does not fade under pressure, or has a temperature above 38C (or above 38C in a baby under three months) should be seen by a doctor promptly, regardless of teething.
Why these two things get confused so often
The confusion has a simple explanation: the teething years (roughly 4 months to 3 years of age) are the same years when young children encounter most of their early viral and bacterial illnesses. When something is happening continuously for that long, it will naturally coincide with illness after illness. The association becomes ingrained as cause and effect, when in reality the timing is coincidental.
Older health advice also played a role. For decades, teething was blamed for a wide range of symptoms, and this belief passed from generation to generation. Even some health professionals grew up hearing it. It takes time for corrected evidence to replace deeply held assumptions. Current NHS and AAP guidance is clear: teething causes local mouth and gum symptoms only.
The safe approach: investigate both, dismiss neither
The most practical way to think about this is simple. If your baby is teething and showing only the symptoms in the first list above (drooling, gnawing, mild gum inflammation, fussiness, possibly softer stools), you can manage those symptoms with teething aids, cool things to bite on, or infant paracetamol or ibuprofen for significant discomfort if your baby is old enough.
If your baby has any symptoms from the second list, treat those independently of the teething. A fever of 38C or above means: take the temperature, check your baby's overall demeanour, and call your GP or NHS 111 if you are unsure, exactly as you would if no tooth were involved. The tooth does not change the equation.
The reassuring thing here is that you do not have to choose. Your baby can be teething and have a normal viral illness at the same time. You treat the illness and you manage the teething discomfort separately. One does not explain away the other.
Managing teething discomfort
The NHS recommends several approaches for teething discomfort that are well-supported by evidence.
- Give your baby something cool and firm to chew on: a chilled (not frozen) teething ring, a cold clean flannel, or a teething toy that has been in the fridge for a short time. Avoid anything that could be a choking hazard.
- Gently rub the gum with a clean finger.
- For babies over three months, sugar-free teething gel (such as those containing lidocaine) can provide short-term relief. Use sparingly and check the age guidance on the packaging.
- Infant paracetamol or ibuprofen can be used for significant distress if your baby is old enough for the dose (always check the label or ask your pharmacist). These are medicines for pain relief, not for routine teething management.
- Avoid teething products containing aspirin (not appropriate for children), homeopathic teething tablets (no good evidence), and amber teething necklaces (a strangulation and choking hazard).
When to see a doctor during the teething years
Teething is not a reason to stay home from the GP. If your baby has a temperature of 38C or above, see a doctor. If your baby has been unusually unwell for more than 48 hours, see a doctor. If your baby has vomiting, persistent diarrhea, a rash, or difficulty breathing, see a doctor or call 999 or go to A&E depending on severity.
Your instinct as a parent matters. If something does not feel right, act on it. "They're just teething" is not a complete answer when your baby seems genuinely unwell.
Frequently asked questions
Can teething cause a high fever?
No. Multiple large studies have found that teething does not cause a fever of 38C or above. A high temperature during teething is caused by a separate illness, not the tooth. Any temperature of 38C or higher should be assessed the same way you would at any other time, regardless of whether a tooth is coming through. Do not wait to see if it settles on its own when your baby has a true fever.
Does teething cause diarrhea?
The evidence does not support teething as a cause of true diarrhea. Some studies have noted slightly looser stools in a small number of teething babies, possibly related to swallowing extra saliva. However, frequent watery stools are not a teething symptom and should be assessed by your doctor, as they can indicate a gastrointestinal infection that needs treatment.
How do I know if my baby is teething or sick?
Teething causes drooling, gum rubbing, gnawing, mild gum inflammation, and fussiness. It does not cause a temperature of 38C or higher, vomiting, significant diarrhea, ear infections, rashes, or cold-like symptoms. If your baby has any of those, investigate it as a separate illness regardless of whether they are also teething. The two can and do happen at the same time.
Should I still see a doctor if I think it is just teething?
Yes, if your baby has symptoms that go beyond what teething actually causes. A temperature of 38C or above, persistent vomiting, significant diarrhea, a rash, ear pulling with a fever, or a baby who seems unusually unwell all warrant a call to your GP or NHS 111. Teething alone does not explain those symptoms, and they should always be taken seriously.
What temperature is normal during teething?
Studies suggest a very slight elevation in baseline temperature during active teething, typically no higher than 37.5C. A temperature of 38C or above is the clinical definition of a fever and is always the result of illness, not teething. If your thermometer reads 38C or higher, treat it as a fever and contact your GP or NHS 111 if you are not sure what to do next.
Can teething cause vomiting?
No. Vomiting is not a teething symptom. If your baby is vomiting, this is caused by something else entirely and should be investigated. Repeated vomiting in a baby, especially combined with other symptoms such as a fever, significant diarrhea, or lethargy, always warrants medical advice without delay.
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