In rare cases, children can develop anaphylactic allergies to previously tolerated foods after receiving blood products via transfusion, report the authors of a case study published in CMAJ (Canadian Medical Association Journal). "It is very unusual to identify someone who experienced passive transfer of allergy from blood products," says Dr. Julia Upton, The Hospital for Sick Children (SickKids), Toronto, Ontario. "Importantly, this condition has an excellent prognosis and typically resolves within a few months. Blood donors who have food allergies can transfer immunoglobulin E, an antibody that reacts against allergens, from blood products such as platelets. This is rare."