Ask most parents of a teething baby whether teething causes fever and diarrhoea, and the majority will say yes. This belief is so widespread and so confidently held that it influences clinical practice: many parents (and some clinicians) automatically attribute fever and loose stools in the 6-30 month age range to teething. The research tells a more complicated story.
Healthbooq covers infant health and the evidence behind common parenting beliefs.
What the Research Shows
The most rigorous prospective study of teething symptoms was conducted by Michael Macknin and colleagues at the Cleveland Clinic, published in Pediatrics in 2000. Macknin tracked 125 infants through 475 tooth eruptions, recording symptoms daily and comparing periods of eruption to non-eruption periods in the same children.
Symptoms genuinely associated with teething in this study: increased drooling, finger sucking, gum rubbing, irritability, and wakefulness. Mild temperature elevation (up to 37.9°C) was also associated.
Symptoms not found to be significantly associated with teething: fever above 38°C, diarrhoea (loose stools), rash, decreased activity, or decreased appetite.
A 2016 systematic review by McIntyre and McIntyre, examining pooled evidence from multiple studies, reached broadly similar conclusions: mild local gum symptoms are consistently associated with teething; systemic symptoms like high fever and diarrhoea are not.
Why Teething Gets Blamed for Fever and Diarrhoea
The association between teething and these symptoms in parental experience is partly explained by coincidence of timing. The teething period (6-30 months) coincides almost exactly with the period of highest frequency of viral infections and gastroenteritis in infants. Infants in this age group are at nursery or encountering new environments, building their immune experience, and averaging 8-10 respiratory infections per year. When a tooth emerges in a child who also has a viral illness, it is natural to attribute all symptoms to the tooth.
Confirmation bias also plays a role: parents who believe teething causes fever will remember the instances when fever occurred with teething and not recall the many eruptions that were uneventful.
The Clinical Importance of Getting This Right
Fever above 38°C in an infant requires assessment because the differential diagnosis is not teething – it is viral illness (very common, usually self-limiting), bacterial infection such as ear infection or UTI (not self-limiting, may require antibiotics), or in rare cases a more serious infection. Misattributing fever to teething delays this assessment.
The practical guidance: treat a febrile child who is teething exactly as you would treat any other febrile child. Assess the overall clinical picture. Do not assume the fever is benign simply because teeth are erupting. If the fever exceeds 38°C and particularly if the child is under 3 months, seek same-day medical assessment.
Diarrhoea warrants its own assessment if it is severe, contains blood, is associated with signs of dehydration, or persists for more than 5-7 days. The eruption of a tooth does not change this.
What Teething Actually Causes
The localised gum symptoms are real: the gum tissue over an emerging tooth becomes red, swollen, and tender as the tooth approaches the surface. This causes irritability, drooling, and the desire to bite on firm objects to relieve counter-pressure. These symptoms typically peak in the 3-5 days around tooth emergence and then resolve.
The systemic symptoms parents most commonly attribute to teething – fever, diarrhoea, runny nose, rash – are not caused by teething and require separate clinical evaluation.
Key Takeaways
There is widespread belief that teething causes fever and diarrhoea, but the evidence does not support a causal relationship for significant symptoms. Teething may be associated with a slight temperature elevation (up to 37.9°C) but does not cause fever above 38°C. Loose stools are commonly reported by parents during teething but have not been consistently confirmed in prospective studies. The clinical risk of attributing fever or diarrhoea to teething is that a genuine illness (ear infection, UTI, viral gastroenteritis) is missed. Any fever above 38°C in a teething child requires the same clinical assessment as fever in any other child.
