Anaphylaxis can be induced by the passive transfer of immunoglobulin E (IgE) from blood products. Clinicians should be mindful of this rare mode of transmission in the evaluation of children who react to previously tolerated foods, according to the authors of a case study published online April 7 in the Canadian Medical Association Journal.

Joyce Cheung Yee Ching, MD, from the Department of Pediatrics, Rouge Valley Health System in Toronto, Ontario, Canada, and colleagues report the case of an 8-year-old boy who underwent multiple blood product transfusions as part of his treatment for medulloblastoma and subsequently experienced two separate allergic reactions to food caused by passive transfer of food-specific IgE from a pooled platelet transfusion.
In the first reported case of two separate allergic reactions to food, the patient initially experienced anaphylaxis within minutes of eating salmon. One week later, he developed an allergic reaction to peanuts. The patient tested positive for specific IgE to salmon and peanut by ImmunoCAP. In addition, skin prick testing was positive for peanut, salmon, mixed fish, and tree nut mix, the authors write.

Because the patient previously ate fish and nut products routinely without effect, the treating clinicians suspected passive transfer of IgE. “After being notified of our suspicion of passive transfer of allergy, Canadian Blood Services investigated the event and contacted all associated donors,” the authors write. One donor described a severe allergy to peanuts, tree nuts, shellfish and all fish, including salmon. Although there were no remaining donor blood products to test for specific IgE, the source of the passively transferred IgE was inferred to be a pooled platelet transfusion suspended in about 200 mL of plasma from the atopic donor, they write.

Less than 6 months after the initial allergic reactions, specific IgE to both salmon and peanut was undetectable and both foods had been successfully reintroduced into the patient’s diet, the authors report.

Passive transfer of allergy from blood products is unusual, the authors stress. First-line treatment with epinephrine is recommended for acute reactions, and the long-term prognosis is excellent. “However, it is unclear how best to avoid passive transfer of allergy from blood products,” they write. “Canadian and American blood service organizations do not defer donors for having a history of allergy, but donors are deferred if they have symptoms of allergies on the day of donation.” In addition, they explain, self-reported allergies by questionnaire at the time of donation have not been shown to correlate with or predict the actual serologic levels of IgE antibodies.

The clinicians did inform the hospital’s transfusion service of their suspicion of passive transfer of specific IgE, which “resulted in an understanding of the potentially transferred antibodies in our patient and the exclusion of the atopic donor from future donations.”
The authors conclude that “[t]here is no simple way to prevent these rare cases of passive transfer of IgE antibodies without losing safe donors.” Reporting suspected passive sensitization causing food allergy can lead to increased safety of the blood supply, they note. In addition, food allergy from passive transfer of IgE “is worth identifying to avoid unnecessarily prolonged avoidance of foods.”