Landon cannot eat 27 fruits, vegetables, milk and soy products, grains and meats. If he does, he is in excruciating pain. Then, for days afterwards, his body fights the proteins in the food, damaging his gut and causing such dangerous vomiting and diarrhea that he runs the risk of going into a septic-like shock.
Experts have no idea how many children suffer from FPIES. Most will outgrow it in four or five years, but Landon's case is so severe, no one can predict his prognosis, according to Schultz.
"It's unclear how big the population is -- we don't know," said Dr. Jonathan Spergel, chief of CHOP's allergy division, who estimates perhaps 1 in 100,000 children have the syndrome.
"My guess is we are better trained at recognizing it, and therefore the disease is rising," Spergel said.
Processed foods, fewer probiotics, preservatives and the use of antibiotics may all play a role, he said, but research in this type of food allergy -- which may behave like an autoimmune disease -- is still in its infancy.
"FPIES is not like the classic food allergies where you eat and it occurs seconds later, like with a peanut allergy," he said. "The reaction is delayed. That's what makes it hard to diagnose."
Doctors can test fairly accurately for food allergies with a skin and blood test, but most cases of FPIES turn up negative.
"The gold standard is to give a child food and watch for their reaction," he said. "But it's not pleasant to see them get sick, so we work primarily on history, and families describe if they ate this food and had a reaction. We tell them to try this one food for a week and then the next one."
When Schultz tried to introduce sweet potatoes into Landon's diet last September, he had violent reaction that landed back at CHOP for five days.
Other families have struggled to keep their children nourished and healthy.
Neveya O'Donnell was diagnosed with FPIES when she was 8 months old, after she began bottle feeding. Now, at 17 months old, she is less than 28 inches long and weighs 16 pounds.
She's been fed with nasal and gastric tubes that "never stayed in," according to her mother Renee O'Donnell, an optician from Eau Claire, Wis.
"Unfortunately this has not helped her stay on the growth charts," said O'Donnell, 28. "She continues to fall farther and farther below the line."
Right now, Neveya can only take Neocate JR, which costs $65 a can. Her mother also fought to get insurance to pay.
"We had an in-hospital food trial for lamb and bananas at the beginning of December -- lamb caused skin problems," she said. "But when we did the bananas she went into shock within four hours. This is a typical reaction to all the foods we have tried."
Responding to families like the O'Donnells, who help with FPIES Family United Fund, has inspired Schultz.
"I turned from mourning all the time, to feeling empowered," she said. "I feel like I am helping others, giving a place for the families in our community."
Life hasn't been easy for her family. The couple had a car accident when Schultz was 9 months pregnant and her husband Chris had spinal surgery, and is now unemployed. They moved out of their house and are renting it to decrease their expenses, because one parent had to stay home with Landon.