(NEW YORK) -- Tyler Trovato loves his peanut butter and jelly sandwiches with a glass of milk, but if he diverges from that and only a handful of other foods, the 6-year-old goes into a fit of vomiting and lethargy so severe that he has to go to the emergency room.
The St. James, N.Y., first-grader is allergic to just about everything else -- chicken, turkey, rice, sweet potatoes and bananas, among others. As a toddler, he was even allergic to his mother's breast milk and she was a vegetarian.
Since he was 18 months old, he has had to be hospitalized before he can try a new food.
If he ingests a food he is allergic to, Tyler begins to have stomach pains about two to four hours after ingestion and then vomits, sometimes so violently he bleeds. Diarrhea follows and a then a shock-like response.
"He becomes pale, lethargic, doesn't talk and usually stumbles when he walks," said his mother, Jennifer Trovato, 37. "When he reacts he needs fluids. The hospital usually gives him saline, steroids and sometimes Benedryl. He doesn't require an epi-pen but his allergic reaction can be life threatening."
Peanuts and dairy products are notorious offenders for children with food allergies, but few parents and doctors are aware of a much more insidious food allergy that many in the pediatric community have never heard of.
Tyler has food protein induced entercolitis syndrome or FPIES. The allergy does not cause a typical immune response and therefore is often missed by pediatricians and allergists.
Experts have no idea how many children suffer from FPIES and there is no diagnostic code to help doctors identify it.
In FPIES, there is an allergic reaction in the gastrointestinal system. The most common triggers are milk and soy, but any food -- even rice and oats -- can cause a reaction.
Unlike most food allergies, an FPIES reaction is delayed and usually begins two hours after ingestion of food culprits.
In an IgE mediated food allergy, a child develops symptoms almost immediately after eating. And when blood and skin tests are carried out, there is a positive marker.
A non-IgE mediated food allergy like FPIES is especially difficult to diagnose because standard skin and blood testing for specific IgE are routinely negative.
Tyler saw two pediatric allergists and two gastroenterologists before anyone could figure out what was making the little boy so sick because all the standard allergy tests came back negative. Finally, at 18 months, he was diagnosed.
"It was stressful for us as parents," said Jennifer, a kindergarten teacher. "We knew there was something wrong. Now we are part of a study and we are glad to do it, educating others."
The mother of another boy with FPIES, Fallon Schultz of Redbank, N.J., started the International Association for Food Protein Enterocolitis (IAFFPE) so that parents and doctors can learn more about these allergies.
Her son Landon, now 4, can eat only seven foods, along with elemental formula.
One of the association's goals is to obtain an ICD-9 code to help classify an FPIES diagnosis, assist researchers in tracking or identifying patients for clinical studies and to develop new treatments.
Copyright 2013 ABC News Radio