In many classrooms across the country, teachers send flyers home requesting that families not send certain treats to school because of kids who have food allergies. Peanuts are the most common culprit. But just how many kids get food allergies? Dr. Avni Joshi, a Mayo Clinic allergist, performed a study that offers some answers to that question.

Again, how common are peanut and other food allergies? Until a recent study, no one really knew.

"This is the first study which has found the true incidence and prevalence of food allergies in the United States," says Dr. Joshi.

She says their study shows that food allergies vary based on age. So as an infant, milk is the most common food allergy because that’s the most common first food introduced for a baby. The second most common, between ages 1 and 4, is peanuts. And, in adults, to our surprise, we found shellfish allergy was the most common food allergy in adult patients.

They also found that food allergies are more common in males of all ages, and, for most healthy kids, introducing potential allergenic foods, such as peanuts, early may help prevent allergies from developing.

"This will help pave the way for our governing bodies to make recommendations for introduction of allergenic food," says Dr. Joshi.