Landon's physician, Dr. Jonathan Spergel, chief of CHOP's allergy division, 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," he told ABCNews.com last year when Landon was first being treated.
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.
Many mothers are finding renewed hope through the foundation.
Gracie Woodward is being treated at Stanford University's Lucille Packard Medical Center. From the time she was 6 months old, she went into hypovolemic shock every time she tried a new food. Hypovolemic shock occurs when blood and fluid loss is so severe that the heart is unable to pump enough blood to the body.
"One bite and she would get a reaction," said her mother, Lisa, 31, of Folsom, Calif.
Doctors said she would outgrow it when she was a year old, but now she is 29 months, and she requires a feeding tube so she can supplement her diet with formula.
"Now she can do some food like wheat and turkey, chicken and potatoes, but there's so much she can't have," said Woodward. "She also has trust issues with food because it made her so sick. We have to work with her."
Now her mother sits on the IAFFPE board as vice president of outreach. More than 400 parents with FPIES children now connect on the foundation's Facebook page.
"It's important to save families from what we went through," said Woodward, who is pregnant with a second child and whose husband had FPIES. "And studies may help our kids and grandkids."
Experts say many children outgrow FPIES, but Maya Rabban is now 12 and still has the disorder. She is treated at Mt. Sinai Hospital in New York and her mother, Liz Rabban, has been an adviser to the foundation.
Maya began to reject food she had been eating around 18 months old. She would begin vomiting, then go into a lethargic state. "We had a little nest on the bathroom floor and stay with her," said Rabban, 43, of Livingston, N.J.
"Nothing has been added since she was 5 -- nothing," said Rabban.
Maya said she eats a lot of soy products, but can also have fruits and vegetables, as well as bread. But like Landon, parties are a challenge.
"There is a bakery we know near us with cakes I can have," she said. "Now that I am older and go to bat mitzvahs -- I eat before I go out."
When she flies, Maya also has a special arrangement with the airport security staff so she can bring her food and water on board.
Her mother said that before the foundation was established, FPIES their doctors knew about the disorder, but didn't have an organization for parent support.
"They have a great team of pediatricians and allergists and internists and researchers now," Rabban said. "Fallon is an absolute godsend. She really rallied the troops."
"I cannot believe how fast we are moving and the momentum is picking up," said Schultz.
In the first year, she raised $50,000 in affiliation with CHOP. Wanting to do something on a larger scale, Schultz created an international organization, working closely with Spergel, who said her energy is "infectious."
Today, the foundation works with experts and mothers from around the globe. IAFFPE has been selected to exhibit this year at the American Academy of Allergy, Asthma and Immunology conference in Orlando, Fla., and to educate physicians and other exhibitors about FPIES.
As for Landon, doctors have told Schultz "not to hold my breath" for the FPIES to go away.
But, she said, "Life has gotten better and it's more manageable."
Landon's preschool has cooperated with his limited eating and let Schultz bring in the giant cake his mother constructed and filled with presents.
"It came out so cool," said Schultz. "He couldn't have even cared that he didn't have cake. And the other children were amazed with the foodless cake.
"We are learning to adjust and how to make his life fun without limitations," she said. "I had the parental joy of preparing it. In the past, it would have been heartbreaking and heart-wrenching."