Doctors have long warned against practices that could spread germs to babies, but a study published Monday in the journal Pediatrics showed that advice might not be founded.
Scientists report that infants whose parents who sucked on their pacifiers to clean them, rather than rinsing or boiling them, developed fewer allergies. They also had lower rates of eczema and fewer signs of asthma.
The study was conducted in Sweden, and doctors at the University of Gothenburg followed a group of about 180 children from birth. By the age of 18 months, about a quarter of the children had eczema, and 5 percent had asthma.
The children of parents who shared their saliva were significantly less likely to develop those conditions. Analyses of the children’s saliva also showed patterns that suggested the practice had altered the kinds of microbes in their mouths.
The children were additionally protected if they were born traditionally. Children who were delivered through Caesarean section and whose pacifiers were rinsed or boiled had the highest prevalence of eczema, nearly 55 percent.
The study could not prove that sucking on the babies' pacifiers directly caused the improved health outcomes, though it suggests an overly disinfected environment increases the harm of minor threats.
Dr. William Schaffner, an infectious diseases expert at Vanderbilt University told The New York Times that the practice could just be an indicator that the parents are more relaxed about dirt and germs.
“I wonder if the parents that cleaned the pacifiers orally were just more accepting of the old saying that you’ve got to eat a peck of dirt," he said. "Maybe they just had a less ‘disinfected’ environment in their homes.”