Diarrhea is not officially recognized as a teething symptom. The American Academy of Pediatrics states plainly: “Teething does not cause fever, diarrhea, diaper rash or runny nose.” Yet many parents notice looser stools when a tooth is coming in, and at least one longitudinal study published in the AAP’s own journal found that diarrhea was statistically associated with tooth eruption. So the real answer is more nuanced than a simple yes or no.
What the Research Actually Shows
The disconnect between what parents observe and what pediatric guidelines say comes down to how strong the link is. A prospective study that tracked infants through their primary tooth eruptions found that irritability, increased drooling, runny nose, loss of appetite, diarrhea, rash, and sleep disturbance all occurred more frequently during eruption windows than at other times. That suggests a real pattern, not just parental imagination.
But “associated with” is not the same as “caused by.” The leading theory is that babies drool far more when teething, and swallowing excess saliva can loosen stools slightly. Babies in the teething age range (roughly 4 to 30 months) are also putting everything in their mouths, which introduces bacteria and viruses that cause genuine digestive illness. Because these behaviors overlap with teething, it’s easy to blame the tooth.
The important distinction pediatricians draw is between mildly loose stools and true diarrhea, which involves frequent watery bowel movements. Teething might be linked to the first. It does not cause the second. If your baby has watery diarrhea multiple times a day, something else is going on.
Symptoms Teething Actually Causes
Teething pain typically starts around 4 months of age, and each new tooth brings a window of discomfort lasting about 3 to 8 days, peaking in the few days before and after the tooth breaks through the gum. During that window, the well-established symptoms are gum swelling and tenderness, increased drooling, irritability, and a desire to chew on everything. Some babies also lose interest in feeding and sleep poorly.
Teething does not cause fever. This is one of the most persistent misconceptions. A slightly warm forehead from fussiness or crying is not the same as a fever. If your baby’s temperature is elevated, treat it as a sign of illness, not teething.
What Else Causes Diarrhea at This Age
The 6- to 12-month window when most teeth arrive is also prime time for a baby’s first stomach bugs. Viral gastroenteritis, commonly called stomach flu, is the most frequent cause of infant diarrhea. Norovirus and rotavirus are the leading culprits. Babies in daycare are also at higher risk for parasitic infections like giardiasis.
Other common triggers include bacterial infections from salmonella or E. coli, a side effect of antibiotics your baby is taking for an unrelated illness, and dietary changes. Introducing new solid foods during this period can temporarily upset digestion, and the timing often lines up perfectly with tooth eruption, reinforcing the idea that teething is to blame.
This overlap is exactly why pediatric organizations are cautious about linking diarrhea to teething. Attributing diarrhea to a harmless process like teething can delay treatment for an infection that actually needs attention.
Signs of Dehydration to Watch For
Regardless of the cause, diarrhea in a baby can lead to dehydration quickly. The most reliable signs are dry mouth and lips, no tears when crying, skin that stays pinched up instead of snapping back when you gently pinch the belly, and a generally ill appearance. If you press lightly on your baby’s sternum and the skin takes more than two seconds to return to its normal color, that’s another red flag.
Two or more of these signs together suggest a fluid loss of at least 5 percent of body weight, which needs medical evaluation. A single episode of loose stool during teething is not concerning. Multiple watery stools in a day, especially with any of the signs above, warrants a call to your pediatrician.
Safe Ways to Ease Teething Discomfort
If your baby is fussy from teething, the safest options are also the simplest. Gently rubbing or massaging swollen gums with a clean finger provides immediate counter-pressure that many babies find soothing. A firm rubber teething ring (not liquid-filled) gives them something safe to chew on. The ring should be cool but not frozen, since a frozen teether can actually hurt tender gums.
Numbing gels containing benzocaine are not recommended for infants. The FDA and the AAP both advise against them due to safety risks. Homeopathic teething tablets have also drawn FDA warnings. Stick with the mechanical approaches: clean fingers, rubber teethers, and a cold washcloth to gnaw on. Always supervise your baby with a teething ring to prevent choking.
The Bottom Line on Teething and Diarrhea
Slightly looser stools during teething are common enough that researchers have documented the pattern. But true diarrhea, the kind that’s watery and frequent, is not caused by a tooth pushing through a gum. The timing coincidence is strong because babies start teething right when they’re also exploring the world with their mouths, eating new foods, and encountering their first infections. If your baby has mild loose stools for a few days around a new tooth and is otherwise happy and hydrated, there’s little reason to worry. If the diarrhea is persistent, watery, or paired with fever, the tooth isn’t the explanation.