Meet Tylor Savage, a 12-year-old boy who has to eat the same thing every day (chicken or tuna with carrots and potatoes, apples and grapes) because he is allergic to almost every food:

By the time he was 10, Tylor’s situation was desperate. He was passing out, going into convulsions and passing blood from both ends of his digestive tract. His weight was down to less than 50 pounds, his growth stunted, his body little more than skin and bones.

His mystified doctors took out his appendix, thinking that might be the problem, but he showed no improvement.

Last September, specialists at Great Ormond Street Hospital in London, where he’d been undergoing tests since April 2006, realized that what Tylor had wasn’t a stomach virus but an extremely rare condition called eosinophilic enteropathy. [...]

They took him off all food, feeding him a liquid formula through a gastric tube inserted through his nose. They then introduced him to one food at a time, making sure he could tolerate it before adding another. Recently, tuna joined chicken as a protein source.

Link - Thanks Andrew Lawandus!