Many children may become allergic to peanuts before they first eat them, and skin exposure may contribute to early risk, according to a study.

Mount Sinai researchers found that early in the process of developing an allergy, skin exposure to food allergens contributes to "sensitization," which means the skin is reactive to an antigen, such as peanuts, especially by repeated exposure.

Previous studies have shown that children may first become allergic when exposed to peanut proteins through breast milk or in house dust, but this recent study adds skin exposure to the list of culprits that make a child allergic by the first time they taste a peanut. The results also make elements of the human immune system in the skin targets for future treatments or preventive efforts.

"The peanut protein responsible for most allergic reactions in humans is seen as foreign or dangerous by the immune system of the skin," said Cecilia Berin, associate professor of pediatrics at the Icahn School of Medicine at Mount Sinai. "Blocking those immune pathways activated in the skin prevented the development of peanut allergy in the mice, and our next step will be to confirm this in humans."

For the study, researchers exposed mice to peanut protein extract on the skin and observed that repeated topical exposure to peanut allergens led to sensitization and a severe, whole-body allergic reaction upon a second exposure.

The data found that peanuts are allergenic due to inherent components the lead to a more robust immune response. These findings suggest that skin exposure to food allergens contributes to sensitization to foods in early life.

"This research helps us to understand why peanut, out of the many foods in our diet, is such a common cause of food allergy," said Berin. "If we identify how the immune system recognizes peanut as a danger, we may eventually learn how to block that pathway and prevent the food allergy altogether."

The findings were published in the Journal of Clinical Investigation.