The number of children with food and digestive allergies has increased by 18 percent over the past decade, a new report shows, underscoring a trend reported by concerned parents and teachers.

The number of kids under 18 with those allergies climbed from 2.3 million in 1997 to 3 million last year, according to a report released today by the Centers for Disease Control (CDC). Some 90 percent are caused by just eight foods: milk, eggs, peanuts, tree nuts, fish, shellfish, soy and wheat.

The findings are based on a national health survey of the parents of 9,500 children who were asked whether their kids had experienced a digestive or food allergy in the previous year. Because the results aren’t based on allergy diagnoses, that makes it unclear whether the rise is real or reflects a greater awareness of the condition, says CDC statistician Amy Brandum, who co-authored the report.

She notes, however, that previous studies have documented an increase in peanut allergies. "I didn’t know anybody in my elementary school with [allergy] problems," Brandum says, "and now there are schools assessing how many classrooms are affected, and it's not insignificant."

Among the possible reasons for the rise in food allergies, she says: Growing use of hygiene products that reduce children's exposure to immune-boosting microbes, and rising temperatures that are spurring the growth of environmental allergens, such as ragweed, that produce cross-reactions with food. Cross-contamination in food manufacturing facilities, and allergens transmitted through breast milk may also play a role, Brandum says.

In addition to potentially severe reactions, food allergies are a concern because of their link to asthma and the skin condition eczema. Children with food allergies are two to four times more likely to have those conditions than other kids, the report found.

(Image by iStockphoto/Joe Cicak)