Teething does not directly cause diarrhea. Despite how widespread this belief is among parents, major pediatric organizations including the American Academy of Pediatrics are clear: teething does not change the way your baby’s gut works. The timing overlap between new teeth and loose stools is real, but the connection is coincidental rather than causal.
Why the Belief Is So Common
Most babies start cutting teeth between 4 and 7 months of age, which is exactly when they begin putting everything in their mouths, losing protective antibodies passed from their mother, starting solid foods, and spending more time around other children. All of these changes independently raise the risk of picking up a stomach bug or reacting to a new food. When diarrhea shows up around the same time a tooth breaks through, it’s natural to connect the two.
Studies do show that many teething babies experience systemic symptoms. One clinical study of children aged 4 to 36 months found that 68% of babies with erupting teeth had general symptoms like drooling, fever, or diarrhea. Diarrhea alone appeared in about 8% of teething children, while the combination of fever and diarrhea showed up in another 8%. But the presence of a symptom during teething doesn’t mean teething caused it. Babies in this age range get sick frequently, and tooth eruption happens dozens of times across these same months.
What Teething Actually Does
The symptoms that teething reliably produces are local and mild. Swollen, tender gums. Extra drooling. Irritability that typically lasts a few days before and after the tooth breaks through, about a week total. Some babies chew on their fingers or refuse food temporarily.
One persistent theory suggests that excess saliva from teething gets swallowed and loosens stools. This idea has never been supported by clinical evidence. The volume of extra saliva a baby produces during teething is small relative to their overall fluid intake, and the digestive system handles saliva without difficulty. Pediatric dental professionals consider drooling, mild temperature elevation, and fussiness to be plausible teething effects, but they do not include diarrhea on that list.
What’s More Likely Causing the Diarrhea
If your baby has loose, watery stools while teething, something else is probably responsible. The most common causes of diarrhea in infants during this age window include:
- Viral infections: Norovirus and rotavirus are the leading causes of infant diarrhea. These spread easily in daycares and family settings.
- Bacterial infections: Salmonella, E. coli, and similar bacteria can enter through contaminated food, water, or the objects babies constantly put in their mouths.
- New foods: Introducing solids often coincides with teething. A baby’s digestive system may react to unfamiliar proteins or fibers.
- Formula intolerance: Cow’s milk protein and soy protein, common formula ingredients, can trigger digestive trouble in some babies.
- Antibiotics: If your baby is on medication for an ear infection or other illness, diarrhea is a common side effect.
- Parasites: Giardia and similar infections spread in daycare environments and cause persistent loose stools.
Because babies in the teething age range are constantly exploring with their mouths, they’re exposed to bacteria and viruses at a much higher rate than before. This alone explains why diarrhea clusters around the same months teeth are coming in.
Loose Stools vs. True Diarrhea
Babies, especially breastfed ones, naturally have soft stools. A slightly mushier diaper during a fussy teething day isn’t the same as diarrhea. True diarrhea in an infant means watery stools that are noticeably more frequent than your baby’s normal pattern. If you’re changing significantly more diapers than usual and the stool is liquid rather than just soft, that’s diarrhea, and it points to an infection or dietary issue rather than a tooth.
The Fever Question
The same misattribution happens with fever. Parents often assume a warm baby with sore gums has a “teething fever,” but the AAP states that teething does not cause true fevers. A normal body temperature sits around 98.6°F (37°C). Fever is defined as 100.4°F (38°C) or higher. Teething may cause a very slight rise in temperature that stays below that threshold. If your baby hits 100.4°F or above, that’s an infection, not a tooth. Cleveland Clinic pediatricians are direct on this point: a fever is a sign of infection, not teething.
This matters because dismissing a fever or diarrhea as “just teething” can delay treatment for an actual illness. Babies can dehydrate quickly from diarrhea, and infections that cause both fever and loose stools need attention.
Soothing Teething Pain Safely
For the symptoms teething does cause, safe options are straightforward. A clean, chilled teething ring or cold washcloth gives your baby something to press against sore gums. Gently rubbing the gums with a clean finger can also help. If your baby seems genuinely uncomfortable, infant acetaminophen is an option your pediatrician can guide you on for dosing.
One important safety note: do not use over-the-counter numbing gels containing benzocaine on babies. The FDA has warned that these products should not be used on children under 2 years old. Benzocaine can cause a dangerous blood condition called methemoglobinemia, which severely reduces the oxygen your baby’s blood can carry. The FDA considers the risk serious enough that it has urged manufacturers to stop selling these products for infant teething entirely. Homeopathic teething tablets containing belladonna have also raised safety concerns and are best avoided.
When Diarrhea Needs Attention
If your baby has diarrhea, whether or not a tooth is coming in, watch for signs of dehydration: fewer wet diapers than usual, no tears when crying, a dry mouth, or unusual drowsiness. The AAP recommends calling your pediatrician if diarrhea lasts more than a day. Watery stools with blood or mucus, diarrhea paired with a fever of 100.4°F or higher, or any signs of dehydration all warrant a call. Attributing these symptoms to teething and waiting them out is exactly what pediatric professionals caution against.