Experts suggest that parents should avoid kissing young children on the mouth to reduce direct bacteria transfer. They also advise against sharing utensils, cups, or food items that have been in one's mouth.
Published Jul 20, 2025 | 7:00 AM ⚊ Updated Jul 20, 2025 | 7:00 AM
Most people don't realise that cavities can spread from one person to another. While cavities themselves aren't contagious, the bacteria responsible for them can be transmitted through saliva.
Synopsis: Streptococcus mutans, a bacterium that feeds on sugar and produces acid, slowly erodes the enamel, leading to dental caries or cavities. Children aren’t born with this bacteria—it’s typically acquired after birth, and the source is usually a parent or close caregiver.
You brush your teeth twice a day, floss religiously, and even limit your child’s sugar intake—but one kiss or shared spoon could be enough to undo all your efforts. It turns out, cavities are more of a family affair than most people realize.
“Don’t kiss your child,” the All India Dental Students Association (AIDSA) warned in a recent statement. “Most people don’t realize that cavities can spread from one person to another. While cavities themselves aren’t contagious, the bacteria responsible for them—especially Streptococcus mutans—can be transmitted through saliva.”
The bacteria that cause cavities can spread from adult mouths to children’s, especially during close contact or routine caregiving practices like kissing on the lips, sharing food or utensils, cleaning a pacifier with your mouth, or even blowing on a baby’s food.
The villain here is Streptococcus mutans, a bacterium that feeds on sugar and produces acid, slowly eroding the enamel on teeth and leading to dental caries or cavities. Children aren’t born with this bacteria—it’s typically acquired after birth, and the source is usually a parent or close caregiver.
Cavities develop when acids produced by bacterial fermentation of dietary sugars break down the tooth enamel. According to dental researchers, Streptococcus mutans plays a central role in human dental decay by generating acid from sugar metabolism, which leads to demineralisation of enamel.
“Simple acts like kissing, sharing spoons or forks, or even blowing on a baby’s food can transfer these harmful bacteria from one mouth to another. That means oral hygiene affects not just themselves, but their loved ones too,” AIDSA explained.
There exists a specific “window of infectivity,” typically between 19 and 31 months of age, during which children are especially vulnerable to becoming colonised by these bacteria. During this critical period, a child’s oral environment is still developing, making them more susceptible to bacterial invasion.
Scientific research backs this up convincingly. A study by Caufield and colleagues in 1993 used genetic analysis to show that most children acquired specific strains of S. mutans directly from their mothers. The study found that the majority of children studied acquired specific strains of S. mutans directly from their mothers, underlining the significance of maternal transmission.
The research demonstrated that initial colonisation of mutans streptococci in children almost always matched the maternal strain, highlighting the reality of direct vertical transmission from mother to infant, often occurring within a defined window of infectivity.
Another researcher found that the many pathways for how this bacteria is passed on and found that everyday parenting behaviors play a major role in the early colonization of harmful oral bacteria in children.
It noted that salivary transfer through common parenting practices—including pre-chewing food, sharing utensils, and kissing—are the main ways young children acquire mutans streptococci, underscoring the urgent need for parental education regarding oral hygiene and the prevention of bacterial transmission.
Studies over the past three decades have consistently confirmed that mothers and other close caregivers are the primary source of transmission of S. mutans to infants through saliva.
Several behaviours have been scientifically linked to the transfer of these bacteria, including kissing a child on the lips, sharing spoons, forks, or cups, cleaning a pacifier with one’s mouth, and blowing on a child’s food.
Children’s enamel is thinner and softer than that of adults, making them more vulnerable to damage. Once the bacteria colonise a child’s mouth, they thrive on sugary foods and can cause long-term oral health problems.
AIDSA stressed the importance of breaking this cycle early: “Once these bacteria colonise a new mouth, they begin to feed on sugars from food and produce acids that damage the tooth enamel, leading to cavities over time. This is especially important in young children, whose enamel is softer and more vulnerable.”
The implications extend beyond individual families, as early childhood caries remains one of the most common chronic diseases in young children. These everyday acts, often rooted in affection and care, are unfortunately also vectors for oral bacteria that can lead to pain, infection, and costly dental treatments.
Prominent dental and pediatric organisations, such as the American Academy of Pediatric Dentistry (AAPD), advise families to avoid such saliva-sharing behaviours. Reducing the transmission of cavity-causing bacteria can significantly lower the risk of early childhood caries.
The AAPD explicitly recommends that adults avoid sharing utensils or cleaning pacifiers in their mouths, and should not blow on children’s food to prevent transmission of harmful oral bacteria.
To further protect children, experts suggest that parents should avoid kissing young children on the mouth to reduce direct bacteria transfer. They also advise against sharing utensils, cups, or food items that have been in one’s mouth. A pacifier should never be cleaned by sucking on it; rinsing with clean water is preferred. Parents should also refrain from pre-tasting or blowing on a child’s food.
Most importantly, caregivers must prioritise their oral health by brushing and flossing regularly and visiting the dentist to reduce their bacterial load and minimise the chance of transmission. This emerging understanding represents a significant shift in cavity prevention approaches, moving beyond individual oral hygiene to consider the interconnected nature of family oral health.
(Edited by Majnu Babu).
