"It is very unusual to identify someone who experienced passive transfer of allergy from blood products," said Julia Upton from the Hospital for Sick Children (SickKids), Toronto. “Importantly, this condition has an excellent prognosis and typically resolves within a few months," she added.

Blood donors who have food allergies can transfer immunoglobulin E, an antibody that reacts against allergens, from blood products such as platelets. "It is important for parents and physicians to be aware of this event in case children have anaphylactic reactions after receiving blood products, particularly after eating peanuts, tree nuts and fish, foods that they could previously consume without reaction," Upton explained.

These reactions -- with symptoms such as facial swelling, throat discomfort or sudden fatigue -- should be treated immediately at an emergency department, said the case study published in Canadian Medical Association Journal (CMAJ).

When there is passive transfer of allergies after blood transfusion, physicians should follow up with the family after a few months to decide the timing of careful reintroduction of the temporary allergens into a child's diet, Upton said.

It is also important for physicians to report suspected cases of passive transfer of allergies to the hospital's transfusion service to investigate the cause and ensure the safety of the blood supply.


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