Getting allergies from transfusion is rare

Specialist calls these side effects ‘extremely’ uncommon and warns that screening could scare much-needed blood donors

An 8-year-old patient at the Hospital for Sick Children who temporarily developed allergies to salmon and peanuts following blood transfusions presents an “extremely rare” case that would be hard to prevent without losing much-needed blood donors, experts say.

“It’s very controversial, how to reduce such a rare event,” said Dr. Julia Upton, a specialist in clinical immunology and allergy at Sick Kids and senior author of a report on the unidentified boy’s case, published Tuesday in the Canadian Medical Association Journal.

“It’s just so rare that you don’t want to discourage people with allergies from donating. These people really are trying to do something that’s good for people.”

The boy received the series of routine transfusions a few years ago while being treated for a cancerous brain tumour. He had no known allergies before receiving the blood products and often ate foods containing both peanuts and salmon.

Within four days of his third round of chemotherapy, the boy experienced fish-induced and peanut-induced allergic reactions that landed him in the emergency room.

He later tested positive for allergies to tree nuts and fish mix and was forced to carry an EpiPen.

But four and a half months later, the four foods were successfully reintroduced into the boy’s diet without causing a reaction.

He was never really allergic, Upton said; the foreign blood just temporarily caused an allergy through an antibody that the boy’s body didn’t normally produce.

“The vast majority of the time, blood really helps somebody and doesn’t cause a problem like this. It’s a challenging balance. Things would be different if we knew that this happened all the time,” Upton said.

It’s only the second known case of allergy transference in Canada in the past decade, and the first to be reported in a child, according to Robert Skeate, associate medical director with Canadian Blood Services, which issues more than one million blood products each year.

According to the report, the first documented case where an allergy was transferred through a transfusion occurred in1919, when the recipient acquired the donor’s allergy to horses.

But Skeate said he’s familiar with only the two most recent cases, detected in the boy at Sick Kids and an 80-year-old woman in 2007.

About 40 per cent of blood donors in Canada admit to having allergies before donating blood, Skeate said.

Eight per cent of those people classify their allergies as severe.

The number of people that could be saved from temporary allergies by screening out such donors doesn’t outweigh the substantial impact a decline in blood donations would have on the availability of blood in Canada, he said.

“The frequency with which a blood donor has allergies is pretty common, and the frequency of this reaction is just vanishingly rare,” he said.

In the boy’s case, Sick Kids’ transfusion services reported the incident to Canadian Blood Services. They then traced the product back to a specific donor. That person, Skeate said, can no longer donate blood.