Suck On This: Pacifier-Licking Parents Have Less Allergic Kids, Study Finds

Admit it, you’ve done this: your kid drops her pacifier on the floor and, too exhausted to schlep to the kitchen sink to rinse it, you just give it a good lick and hand the binky back.

Well, it turns out this not-so-pretty cleaning method you turn to when no one else is looking may, in fact, be one helluva gift for your child’s immune system.

Joe Suspence/flickr

(Joe Suspense/Flickr)

Researchers in Sweden report that “children whose parents sucked on their pacifiers to clean them had one-third the risk of developing eczema (the most common early manifestation of allergy), at 18 months of age, compared to children whose parents did not use this cleaning practice.”

It gets better. Infants who were born vaginally and were lucky enough to have a parent suck clean his or her pacifier got an added boost, the study found: “The prevalence of eczema was approximately 2.5 times lower at 18 months of age in vaginally delivered children whose parents sucked their pacifiers than in caesarean section-delivered children whose parents did not have this habit (20% vs. 54%),” the study says.

The takeaway from the study, published online today in the journal Pediatrics, is this: It looks like early exposure to parents’ saliva may help stimulate a baby’s immune system, and that could mean a lower risk of developing eczema, asthma and sensitivities to certain allergens. The study authors suggest that healthy oral flora is the key here and that the “transfer of oral microbes from parent to infant via the pacifier might be used in primary prevention.”

“It is a support for the hygiene hypothesis, that early microbial exposure is important for normal tolerance development,” lead author Bill Hesselmar, an associate professor at Queen Silvia Children’s Hospital in Gothenburg, Sweden, says via email.

And it’s not only the oral microbes that appear to be protective here.

In a discussion on why parents of children born vaginally appear to be more inclined to lick their children’s pacifiers, the authors speculate that the very nature of the birth itself — the wet, messy reality of vaginal birth compared to the medical sterility of a caeseran section — might somehow be internalized by new parents.

During a vaginal delivery, the baby is exposed to bodily fluids and sometimes soiled with faeces; after a normal delivery the mother and baby will be speedily discharged from the hospital. In contrast, delivery by caesarean section is a strictly sterile surgical procedure followed by hospital stay and substantial medical attention. Theoretically, the ‘sterility culture’ of the hospital may be transmitted to the parents and influence their subsequent care of their baby even when they return home.

In any case, the message is clear. Familial saliva sharing sure looks like a good thing.

And, says Moises Velasquez-Manoff, author of the book, “An Epidemic of Absence: A New Way of Understanding Allergies and Autoimmune Diseases,” “It’s completely consistent with the accumulating evidence suggesting that there are microbes transmitted from parents to children that are good for us.”

He suggests: “Think of it as your inherited microbial wealth — like heirlooms –you need to get them from other humans and the most likely source is from your parents when you’re young.”

When you interrupt that important transfer of microbes, Velasquez-Manoff says, the immune system can get out of whack. In his book, which might also be called, “beyond the hygiene hypothesis,” he argues that modern humans have sanitized out of our lives many critical parasites and microbes that we co-evolved with. As a result, our immune systems have become unable to properly regulate themselves, and we are suffering from a myriad of inflammation-related disorders such as allergies and asthma, but also possibly, as he recently suggested in The New York Times, from autism, because of this sub-optimal immune response.

As far as the pacifier-licking study, Velasquez-Manoff says it may not only be the microbes at work here. “Saliva also has antibodies in it, and if we’re healthy, the antibodies in our saliva send the message to tolerate this.” He offers the example of premastication, noting that before infants ate food from cans and jars, mothers simply pre-chewed food for their babies to eat.

“You transfer both the good microbes and antibodies when you do that,” he said. “But that began changing in the upper classes in the 19th century — and even earlier — when there was a culturally taught disgust toward bodily fluids. That happened with growing affluence.”

The Swedish pacifier study was fairly small, 184 infants, examined at 18 months and again at 36 months. Here are details:

A birth-cohort of 184 infants was examined for clinical allergy and sensitization to airborne and food allergens at 18 and 36 months of age and, in addition, promptly on occurrence of symptoms. Pacifier use and pacifier cleaning practices were recorded during interviews with the parents when the children were 6 months old. The oral microbiota of the infants was characterized by analysis of saliva samples collected at 4 months of age.

Children whose parents “cleaned” their pacifier by sucking it (n = 65) were less likely to have asthma (odds ratio [OR] 0.12; 95% confidence interval [CI] 0.01–0.99), eczema (OR 0.37; 95% CI 0.15–0.91), and sensitization (OR 0.37; 95% CI 0.10–1.27) at 18 months of age than children whose parents did not use this cleaning technique (n = 58). Protection against eczema remained at age 36 months (hazard ratio 0.51; P = .04).

Clearly, more research and a larger study is needed to know precisely the mechanism at work here.

Velasquez-Manoff says it would have been interesting to know what was in the house — a pet, for instance — to figure out if people licking the pacifier after dropping it on the floor might have had a more diverse microbiota. “It would have been nice to know what else these mothers were exposed to during pregnancy,” he said.

Still, the practice of licking your children’s objects clean probably can’t hurt, he says: “I don’t see anything wrong with parents sharing saliva with children. They’re getting it anyway, right? Your kid is all over you.”

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  • So.NH

    Why no mention that this will transmit the bacteria that causes tooth decay?

  • Futo Buddy

    that modern humans have sanitized out of our lives many critical parasites and microbes that we co-evolved with. i think this also applies to cannabis a lot of our problems are related to the supression of this organism that evolved with humans. i liken it to the clownfish and anemone either can survive without the other but both are more successful with their symbiotic species. depriving humans of cannabis is like depriving the anemone of the clownfish.

  • Ana_900

    As a parent of 2 children with food allergies and eczema, no genetic link to anyone in our families, I could say that all these findings, one after the other, are not finding the reason(s) where this immune disorder comes from. My acupuncturist’s theory that is the most convincing for me is that we, as population, keep moving and we get exposed to new food and environment and some people can’t adjust to these changes. Not to mention that most of environment and food changes are the one we are making ourselves with GMO foods and pollution.

    • Reasonable?

      Check out the book “The Epidemic of Absence”.
      That book makes a very compelling argument around environment exposures and the rise in allergic and autoimmune conditions

    • Futo Buddy

      all that roundup we eat seems like its a factor in a lot of these “wheat allergies”

  • Reasonable?

    Back to the future.
    Before “baby food” and pacifers there was pre-mastication.
    Parents prechewed food before giving it to their infant children after weeening.
    So children used to get massive doses of parental saliva with all the immune benefits.
    We look at such practices with distain today, but the evidence seems to be changing our perpectives on these and related habits.

    • Futo Buddy

      just like baby birds