PURPOSE OF THE STUDY.
The study examined the effect of how parents clean their infant’s pacifier on the risk of developing eczema, asthma, or allergic sensitization.
Subjects were from a cohort of 187 term infants recruited into the AllergyFlora study in Gothenburg, Sweden. Mainly, families with at least 1 parent with allergic disease were approached. A total of 184 children were followed up until 18 months of age, and 174 were followed up to 36 months of age. Fourteen percent were delivered by cesarean delivery, 80% had at least 1 parent with a history of allergic disease, and 74% used a pacifier in the first year of life.
When the children were 6 months old, parents were asked: “Does the child use a pacifier?” and “Is it cleaned by boiling, rinsing in tap water, or by the parents sucking on it?” with >1 option possible. A pediatric allergist examined the children and reviewed the medical record at 18 months, 36 months, and when symptoms suggested a diagnosis of eczema or asthma.
Of those who used pacifiers, nearly one-half of the parents (48%) reported they had sucked on the pacifier. By the age of 18 months, 25% of the children had developed eczema and 5% had developed asthma. Sucking the pacifier strongly lowered the risk of eczema (odds ratio: 0.37 [95% confidence interval: 0.15–0.91]; P = .02) and asthma (odds ratio: 0.12 [95% confidence interval: 0.01–0.99]; P = .03). Parents of vaginally delivered infants were more likely to suck the child’s pacifier. The group exposed to both maternal vaginal microbiota and parental oral microbiota via the pacifier had the lowest prevalence of eczema (20%), whereas infants exposed to neither maternal vaginal microbiota nor parental oral microbiota had the highest prevalence (54%). Children who were either vaginally delivered or whose parents sucked on their pacifiers had an intermediate prevalence of eczema (31%). Evaluation of the microbiota present in saliva at 4 months of age according to molecular genetics (terminal-restriction fragment length polymorphism) distinguished patterns of microbes in the saliva depending on pacifier cleaning practices.
Sucking on the infant’s pacifier before it is given to the infant may protect against early development of eczema and asthma. This practice may influence the infant’s oral microbiota composition. At 18 months of age, the prevalence of eczema was ∼2.5 times lower among vaginally delivered children whose parents sucked on their pacifiers than among children born via cesarean delivery whose parents did not suck on their pacifiers (20% vs 54%). Evidence for the transfer of respiratory pathogens according to this practice was not apparent. Dental caries seemed unrelated to close salivary contact.
Although this association does not prove causation, this surprising finding supports the “hygiene hypothesis” and the role of initial (birth) and subsequent (oral) exposures to microbes in modulating immune responses in a favorable manner. In this situation, the sharing of maternal saliva may replicate saliva and oral microbes likely shared by premastication of food by the mother for feeding to the infant, a practice that is now only rarely observed in Westernized societies where processed and sterile infant food is available.
- Copyright © 2014 by the American Academy of Pediatrics