PHILADELPHIA - Eleven-year-old Ashton Ulmer loves hockey. He's also a foodie, but he recently stopped eating nearly everything.

"It just hurt," Ashton said. "I didn't want to eat."

"When he started pushing the plate away and started getting a little frustrated, I knew something else was wrong," said Melissa Ulmer, Ashton's mother. "It was more than just reflux. It was heartburn, belly pain."

Figuring out what's wrong when kids have stomach aches is difficult. In Ashton's case, he was allergic to...

"Milk protein. The cow protein," Melissa shared.

Ashton has eosinophilic esophagitis, or EOE, and milk triggers it.

Dr. Jonathan M. Spergel, a professor of pediatrics at The Children's Hospital of Philadelphia, recently completed a study on the disorder, which causes the body's immune system to turn on itself and reject food.

"It actually hurts to eat," Spergel said.

Spergel's study focused on 20 children with EOE who wore an inch-long patch with milk protein on their backs. It was absorbed through the skin because traditional allergy shots or pills didn't work, and the idea behind the patch was to build up a tolerance to the danger food.

"So, we put the patches on their backs and changed the patches every day," Spergel explained.

After nine months, the doctors reintroduced milk.

"Was the disease still there? For some patients, it wasn't," Spergel said. "Didn't work with all patients, but for some patients, they were now able to take milk, which they couldn't before, which is sort of wonderful."

EOE can create intolerance to all foods and restrict the esophagus, so that swallowing food would be impossible, so doctors say early intervention is critical. This was a phase-2 study, but additional studies are needed to get the FDA's approval.