Oz kid Kaleb Bussenschutt has became one of the most difficult mysteries doctors have ever had to solve. The 5-year-old boy is suffering from an allergy to all types of food.
Kaleb, who cannot eat anything, is able to consume only water and a certain brand of lemonade, and he needs to be fed for 20 hours a day through a machine that pumps nutrients directly into his stomach.
His mother Melissa Bussenschutt said doctors have "no idea" exactly what is wrong with him except that food makes him violently ill and fills his stomach with ulcers.
"He's got severe malabsorption, so he doesn't absorb food. They're doing tests to find out why it is that he can't eat food. It can be really hard.
"If we go out to dinner, to a restaurant, he gets a cup of ice and he'll say 'What are you eating? What does it taste like?' or 'It's not fair'," she said.
His allergy is so severe that he cannot even share pencils with friends in case he accidentally ingests a bit of food left there.
About one in 20 children have some sort of food allergy, but most allergies are mild and many disappear in time, and allergy expert Professor Peter Sly said cases like Kaleb's were "very rare".
Professor Sly is the head of Clinical Sciences at the Telethon Institute for Child Health Research.
"I've heard of severe absorptive problems that do these sorts of things . . . it's often unclear whether it's a true allergy or an intolerance," Professor Sly said.
"The bowel is just so irritable it just can't tolerate normal foods," he added.
The Bussenschutts are trying to raise money for more research, and have organised a bike ride from Melbourne to Adelaide next year.