Get the latest from TODAY

Sign up for our newsletter
 / Updated 
By Erika Edwards

The latest research on allergy prevention in kids will either reassure parents or totally gross them out.

The finding: sucking on your baby’s pacifier to clean it may mean little Olivia or Milo will be less likely to develop allergies.

“The microbes that a child is exposed to in infancy can affect the way their immune system develops,” said Dr. Eliane Abou-Jaoude, an allergy and immunology fellow at Henry Ford Health System in Detroit and lead author of the new study. In this case, it appears those beneficial microbes can come from inside a mother’s mouth.

Abou-Jaoude and colleagues followed 128 new moms for a year and a half after giving birth, periodically asking them how they cleaned their babies’ pacifiers.

Of the 74 whose infants used one, the majority washed them by hand; 41 percent took it a step further by sterilizing the devices. But 12 percent simply popped the binky into their own mouths to clean them.

Through a series of blood tests, researchers found those babies had lower levels of an antibody called IgE by the time they were 10 months old. People who have higher IgE levels are generally more prone to allergies, asthma and eczema.

Some of the children in the study were already at a higher risk because of a family history. About 18 percent of the mothers had asthma, and about 8 percent had eczema.

The research does not prove sucking on a child’s pacifier will prevent allergies. “This was not a cause-effect study,” said Abou-Jaoude. “We can’t say these children won’t develop allergies later on. We only have IgE levels until 18 months of age.”

The research team plans to follow up with the families in the coming years to see whether any of the kids are eventually diagnosed with an allergy. The current research will be presented at a meeting of the American College of Allergy, Asthma and Immunology.

Not all bacteria is bad

The findings boost evidence that exposure to mom’s bacteria in early infancy can be a very good thing. During childbirth, babies are exposed to important bacteria when they’re delivered through the birth canal. A study last year found mothers transmit healthy bacteria to their babies through breast milk. And a 2013 Swedish study found babies whose parents sucked on their pacifiers to clean them were three times less likely to have eczema by the time they were toddlers.

But this does not mean parents should start actively exposing their babies to saliva — their own or anyone else’s.

“Saliva is a very versatile tool,” said Whasun “Sun” Oh Chung, a research professor at the University of Washington School of Dentistry. She studies how the body distinguishes good bacteria from bad bacteria. She points out that saliva can also transmit potentially dangerous germs and cavity-causing bacteria. “We don’t have enough data to see whether the benefits (of this practice) outweigh the harms,” she said.

Abou-Jaoude agrees. “We are not telling parents to clean their child's pacifier by sucking on the pacifier. Bad bacteria can be transferred by a parent sucking on the pacifier and then giving it to their child, exposing them to other infections.”

Still, experts say this kind of research shows most kids do not need to be raised in an extremely hygienic environment.

“A diversity of bacteria in your body, in your mouth and on your skin is likely good, particularly in a baby whose immune system is developing,” said Dr. Wendy Sue Swanson, a pediatrician at Seattle Children’s Hospital.

“Let them play in the dirt,” she said. “Introduce foods to them early in life, and allow them to explore the world in some ways like we used to.”