Parents who clean their baby's pacifier by sucking on it and giving it back to the child might be helping to protect the baby from developing allergies, a small study suggests.

"Ick" factor aside, the transferring bacteria from adults' mouths to infants may help to train their developing immune systems to better recognize true threats rather than overreacting to harmless proteins called allergens, researchers speculate.

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Newborns are exposed to a complex mix of microbes from their mother during childbirth. (Claudia Daut/Reuters)

"Parental sucking of their infant's pacifier may reduce the risk of allergy development, possibly via immune stimulation by microbes transferred to the infant via the parent's saliva," Dr. Bill Hesselmar, an associate professor at Queen Silvia Children's Hospital, in Gothenberg, Sweden, and his co-authors concluded in Monday's issue of the journal Pediatrics.

For the study, researchers examined 184 infants for clinical allergy when any symptoms first occurred, and again at 18 months of age. A subgroup of 174 were followed until 36 months of age.

The researchers chose to include babies from families with at least one allergic parent to try to look for differences in immune responses.

The investigators used DNA fingerprinting of bacteria from parents and babies to obtain "suggestive evidence" of how pacifier cleaning may influence the makeup of bacteria in the infant's saliva.

Pacifier cleaning offered additional and independent protective effects against developing eczema separate from the benefits of a vaginal delivery, when newborns are exposed to a complex mix of microbes from the mother, the researchers said.

Dr. Tom Glass, a professor of forensic sciences, pathology and dental medicine at Oklahoma State University, presented research at the American Society for Clinical Pathology in Boston last November that found a wide range of disease-causing bacteria, fungus and mold on children's pacifiers.

Glass said he's long advocated that parents put a pacifier into their mouth to clean it because adult saliva helps fight bacteria.

The researchers weren't able to specifically identify which bacteria were transferred. They are planning a longer study to see if the pacifier methods could reduce allergy development.

The study was funded by the Swedish Research Council, the Vardal Foundation, the European Commission, the Swedish Asthma and Allergy Association Research Foundation, the Torsten and Ragnar Soderberg Foundation, Gotenburg Medical Society and the Cancer and Allergy Foundation.

With files from The Canadian Press