Why some children develop food allergy remains a mystery. Is it genetic? Is it connected to when certain foods are introduced to a baby, or an increase in eating more processed foods?

A recent study of 1,000 mothers and newborns in Australia could provide some clues.

Researchers analyzed umbilical cord blood at birth and found a link between the presence of hyperactive immune cells in the blood and the baby’s later development of food allergies.

“In at-risk babies, immune cells called monocytes were activated before or during birth,” says study co-author Yuxia Zhang, MD, an immunologist with the Walter and Eliza Hall Institute of Medical Research in Parkville, Australia. “Signals from these cells encourage the development of immune responses by specialized immune cells called T cells that are predisposed to cause allergic reactions to some foods.”

In other words, the study suggests that in some children the immune system is ‘primed’ for allergies at birth.

“Are the immune cells inherently activated at birth because of the baby’s genes or do they become activated at the time of birth or earlier in pregnancy, and how?” wonders study co-author and professor Len Harrison.

Allergy & Asthma Network’s Purvi Parikh, MD, a pediatric allergist and immunologist in New York City, told Yahoo Health the study results show promise.

“The study is very interesting because we already know that allergies are something where the immune system is in overdrive,” Dr. Parikh says. “So the fact that a food allergy is already developing in pregnancy could mean one of two things – it’s either genetic or environmental.”

“Perhaps it may give us insight into things we can do in the prenatal period to help keep children from developing food allergies and lessen the risk,” Dr. Parikh adds.

Future research may involve studying lifestyle habits of moms-to-be during pregnancy, including diet, to understand why the babies developed hyperactive immune cells.