It’s a Pavlovian response—you lick your thumb to clean the pureed peas off your baby’s face. But licking her pacifier clean after she knocked it onto the floor? Ewwww.
Get over it. According to a new study in the journal Pediatrics, that’s exactly what you should do. Parents who perform this protective act might be reducing the kid’s risk of developing allergies.
As explained on MedPageToday.com, the study suggests that transferring the microbes in your mouth to your baby’s mouth could modify its population of bacteria and cultivate a broader immune response to future invaders.
The researchers looked at kids who were 18 months and 36 months. In the younger group, children born to parents who said they cleaned their child's pacifier with their mouths were less likely than those born to parents who cleaned it with water to have asthma and eczema. At 36 months, the association remained for eczema, but not for asthma.
The benefit of this “oral hygiene,” the researchers suggest, might extend to a kid’s nether regions—because the baby swallows the newly transferred parental bacteria, they could affect the microbiology in the intestines, which could improve general gut tolerance.
Infants with less diversity among their gut microbes, according to MedPage Today, are more likely to develop allergies. That suggests that exposing youngsters to a wider variety of microbes could promote immune system function.
As Dr. Amal Assa'ad of Cincinnati Children's Hospital Medical Center told MedPageToday, "[W]e have to let nature play out a little bit and not be too clean and not be forming artificial barriers in the connection between the mother and the infant and the parents and the infant."
"We have to at some point reach a balance where we're making sure we're not predisposing [infants] to infections at the same time [we're making] sure we're giving them what they were naturally expected to get from the parents ... so we end up with a balanced body that doesn't veer towards allergies and doesn't veer towards serious infections and harm."
It’s interesting that, according to the study, the method of birth (cesarean or vaginal) was related to the likelihood of a parent sucking on the pacifier. Vaginal delivery and parental pacifier sucking independently were associated with a reduced likelihood of developing eczema; babies delivered vaginally and whose parents licked their pacifiers had a lower incidence of eczema.
The theory is that vaginal delivery, which also transfers bacteria from mother to infant, has a beneficial effect on allergy resistance.
Regarding the “ick” factor, and the concern that transferring a pacifier from a parent's
mouth to a child's could spread respiratory infection, the study showed no difference in the rate of such infections based on pacifier cleaning practices.
Keep in mind that this study had a relatively small sample size (184 kids), and that it’s relatively difficult to diagnose asthma in early childhood. So a larger study also involving older children is necessary to replicate—and confirm—these results.
But, for now, if you think it’s better to wash your kid’s pacifier under the tap than in your saliva, it’s probably time to think again.