Breast-feeding newborns might limit their allergy to pets later

HOUSTON — Early breast-feeding accompanies a lower risk of pet allergy, possibly because of the way breast milk steers the composition of an infant’s gut microbe mix.

Scientists find that formula-fed newborns have a kind of gut bacterium at levels typically not seen until later in babyhood. These kids also had more signs of pet allergy years later than did breast-fed children, researchers reported February 22 at a meeting of the American Academy of Allergy, Asthma & Immunology.

Breast-feeding has myriad benefits for an infant and influences the mix of microbes in the baby’s intestines (SN: 1/11/14, p. 22). Whether breast-feeding affects a child’s allergy risk has been less clear.

Alexandra Sitarik, a biostatistician at Henry Ford Health System in Detroit, and her colleagues analyzed stored diaper samples from 130 babies who were one month old at the time. The fecal samples revealed that breast-fed infants were colonized by plenty of Bifidobacteria, helpful gut microbes that normally dominate in early infancy. Formula-fed newborns, on the other hand, had high amounts of Lachnospiraceae. While those microbes naturally show up in the gut and are common in adults, they usually don’t appear in substantial amounts until a child is at least six months old, says Sitarik.

Questionnaires sent to the babies’ families revealed that at age 4, the children who had been breast-fed at one month were substantially less likely to react to pets — by coughing, wheezing or experiencing shortness of breath — than were kids who had been fed formula at one month.

“In the infant gut, maybe breast-feeding is preventing this premature shift into adulthood,” Sitarik said. The biological mechanisms that would explain a breast-fed microbiome link to decreased allergy risk are not known, but the timing of the gut microbiome difference between babies makes sense, she says. “We know that the immune system is trained early on.”