Results of a new study show that breastfeeding can reduce pet allergies when a baby grows up. It all comes down to little things called microbes.

Scientists report that newborn babies who are fed formula actually have a different mix of microbes in the gut than breastfed babies. And those microbes are in the formula-fed babies’ intestines long before they should be.

Science has proven breastfeeding to be beneficial to babies in lots of ways, but until this study was released by the Henry Ford Health System in Detroit, the positive effects on pet allergies, though long assumed, were less clear.

Now, in the study presented at the American Academy of Allergy, Asthma and Immunology, scientists say that parents of breastfed babies were far less likely report pet allergies in their children by the age of four than were formula fed babies.

Lead researcher Alexandra Sitarik says breast feeding helps train the immune system early on in life.

“It may be that breastfeeding is preventing this premature shift into adulthood," Sitarik said.