A new Swedish study suggests that parents who want to protect their infants
from developing allergies should try a simple approach to introducing their
children to the wide world of microbes: Just pop their pacifiers into their own
mouths before giving them back to their babies.
Although that may sound disgusting or even risky to some, researchers found
that the transfer of oral bacteria from adults to infants seems to help train
the immune system to ignore germs that don't pose a threat.
"The immune system's purpose is to differentiate between harmless and
harmful," said Dr Ron Ferdman, a paediatric allergist at Children's Hospital Los
Angeles. "If your immune system is not presented with enough microbes, it just
defaults to doing harmful attacks against things that are not harmful, like
food, cat dander or dust mites."
More kids with allergies
A report showed that the number of American children with allergies has increased
dramatically in recent years: about 13% have skin allergies and 17% have
The Swedish researchers set out to learn whether very early microbial
exposure during the first months of life affects allergy development. They found
that children whose parents sucked on their pacifiers to clean them were less
likely to have asthma, eczema and sensitivity to allergens than children whose
parents did not clean the pacifiers this way.
The authors concluded that parental sucking of their baby's pacifiers may
help decrease the risk of allergy caused by transfer of microbes through the
For the study in the journal Pediatrics, 206
pregnant women in Sweden were initially recruited as participants, and 187 of
their infants were included in the research. The scientists sought families with
at least one allergic parent to see if they could identify a different immune
response in the children.
The researchers studied the transfer of microbes in the parents' saliva by
fingerprinting bacterial DNA in 33 infants' saliva, of which 21 had parents who
sucked on their pacifiers.
A total of 187 babies were followed until the child was 18 months old, and
174 were followed until they were 36 months old. The researchers chose to
evaluate the children at those specific points in time because some diseases,
such as eczema, develop early in life, said Dr Bill Hesselmar, an associate
professor at Queen Silvia Children's Hospital, in Gothenberg, Sweden.
Exposed to the world
Introducing solid foods into an infant's diet did not seem to affect the
study results, Hesselmar said. "We found differences in the oral microbial flora
already at 4 months of age, at an age when most children are still on breast
Ferdman, who was not associated with the research, urged caution in
interpreting the results of the study. "It's a small number of babies studied,
so it's hard to generalise," he said.
He also expressed concern that results may not be widely applicable because
the data were taken solely from Swedish participants, who are not a genetically
Other researchers have expressed concern about dirty pacifiers.
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 mould on children's pacifiers. They also
found that pacifiers can grow a slimy coating of bacteria called a biofilm that
alters the normal bacteria in the children's mouths, spurring inflammation and
potentially increasing the risk of developing gastrointestinal problems or even
The value of using a parent's saliva to clean a dirty pacifier has been known
for some time, Glass said. "We have for a long time advocated that if you're at
the Walmart and the baby drops the pacifier, you're better off putting the
pacifier in your mouth [to clean it] because you have immunoglobulin components
that fight bacteria in your saliva."
Glass expressed concern that the researchers did not identify the specific
microbes transferred from parents to the pacifiers. "We don't know what the
parents are actually transmitting to the child," he said.
What should parents do to help prevent allergies in their children? "Babies
need to be exposed to the world, and exposure to the normal microbial
environment is protective," Ferdman said. "Breast-feed for at least four to six
weeks if you can. Don't smoke, and don't expose your children to secondhand
Find out more about the risks and benefits of pacifiers from the American Academy
of Family Physicians.