A 46-year-old man with leukemia was doing well after a bone marrow transplant from his sister — until he ate a kiwi. Suddenly, he had a food allergy that he'd never had before.

Doctors performed hematopoietic cell transplantation from the man's sister, who happened to be allergic to kiwi. (Hematopoietic stem cells are the blood cells that give birth to all other blood cells.) A few weeks after the procedure, the patient ate a kiwi and was surprised at his body's reaction.

"He developed a severe oral allergic syndrome including mouth and throat swelling for the first time in his life," says Dr. Natalie Garzorz of the Department of Dermatology and Allergy at the Technical University of Munich. "Before HCT, he always tolerated kiwi without problems."

Garzorz and a team of researchers studied the new allergic response. Their study was published in the Journal of the European Academy of Dermatology and Venereology.

The researchers isolated the cells in the patient's blood that reacted to the kiwi. Using a process called chromosomal fluorescence in situ hybridization (FISH), they were able to determine that those kiwi-responsive cells originated completely from his sister's donated cells.

This isn't the first time scientists have documented the spread of allergies through HCT. Although it has been described in several reports, this is the first time that researchers have shown that the allergic reaction was triggered by the donor's cells, say Garzorz.

Now that scientists believe that bone marrow transplants can spread an allergy, the obvious question is whether the process can be reversed and transplants can be used to eliminate allergies.

"There is a high probability that allergies can not only be transferred but on the contrary also be cured by HCT from a non-allergic donor, however, this would be only ... in severe cases," says Garzorz.

In addition, she says, this research may be helpful in understanding allergies in general.

"A proper experimental work-up with 'house-made' extracts of every single case of HCT mediated allergy transfer as proposed by us could be helpful in discovering how allergies are spread and treated."

Mary Jo DiLonardo Mary Jo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.