A new study published this week in Pediatrics indicates that more kids than previously thought have a food allergy — including an allergy to milk. Results from the online study of almost 40,000 adults who lived with a child under age 18 showed that food allergy prevalence for respondents was solidly at 8 percent, or about 6 million U.S. children. Previously, experts estimated that anywhere from 2 to 8 percent of kids were affected.

When it came to what the kids were most allergic to, peanuts came in at 25.2 percent, followed by milk (21.1 percent) and shellfish (17.2 percent). Download the abstract here.

According to the Food Allergy and Anaphylaxis Network, a food allergy is the immune system’s reaction to a certain food. The immune system mistakenly reads the food as harmful and creates antibodies to that food. When the food is eaten again, the immune system releases histamine and other chemicals. These chemicals cause the symptoms of an allergic reaction.

This is different from a food intolerance, like lactose intolerance.

Among children with food allergies, 38.7 percent had a history of severe reactions, and 30.4 percent had multiple food allergies.

Study authors told Reuters that they aren’t sure why they saw a rise in food allergies among children, or whether these results indicate an overall increase in food allergies in the U.S. population. But they did note that the odds of a food allergy were significantly associated with race, age, income, and geographic region. In addition, disparities in food allergy diagnosis according to race and income were also observed.

At the end of the day, it's important for parents to know the symptoms of food allergy so if they notice these symptoms, they can get their child appropriate medical treatment, say dietitians.