Researchers are warning that, while rare, it is possible for children who receive blood transfusions to develop new, potentially deadly food allergies.
According to a new case report published in the Canadian Medical Association Journal on Tuesday, an eight-year-old boy with no previous allergies experienced a severe allergic reaction to fish a few weeks after he had a blood transfusion.
The boy was being treated for a type of brain cancer, and part of his treatment involved chemotherapy and receiving blood products, doctors from the Hospital for Sick Children write in the report.
A few weeks after his third treatment cycle, the boy experienced a severe allergic reaction within 10 minutes of eating salmon. His symptoms included swollen lips, reddening of the skin, throat discomfort and fatigue.
He was taken to hospital, where his symptoms resolved within a few hours of receiving an antihistamine.
The report said that the boy had often eaten salmon in the past, and had not had any allergic reactions.
Four days later, the boy experienced an allergic reaction to peanuts, a few minutes after eating a chocolate peanut butter cup. His symptoms included vomiting, lip swelling and extreme fatigue.
Again, his symptoms were resolved a few hours after he was treated by doctors.
According to the report, the boy had often consumed peanut products in the past without any problems.
The boy's doctors suspected that the allergies may have been transferred to the patient, so they notified the Canadian Blood Services, which then contacted all of the donors whose blood was used in the boy's treatment.
It was discovered that one of the donors had a severe allergy to peanuts, tree nuts, shellfish and fish.
Though it is rare, blood donors who have food allergies can passively transfer an antibody called immunoglobulin E (IgE) through their blood. When IgE binds to specific allergens or triggers, it can prompt a range of allergic reactions.
Tests determined the blood donor was the source of the IgE, after which the individual was excluded from making future blood donations.
Approximately five months after the boy experienced the allergic reactions, he was tested again for IgE specific to salmon and peanuts. Doctors found that the levels of IgE were undetectable.
Once six months had passed, the boy's family started to reintroduce salmon and peanuts to his diet.
"Repeat skin testing was not performed because there was no longer a suspicion of allergy," the report said.
Dr. Julia Upton, one of the report's authors, said that, while doctors and parents should be aware of the possibility of a passive allergy transfer, the cases are usually resolved with time.
"People shouldn't be overly concerned about the passive transfer of allergy from blood products," Upton said in a statement. "This condition has an excellent prognosis and typically resolves within a few months."
However, doctors should report suspected cases of allergy transfer to the hospital's transfusion service, so that the source of the allergy can be detected, the report said.
