Allergens transferred in blood more common than previously thought

Anaphylactic reactions to blood transfusions are rare, and their causes remain elusive. In  2003 it was suggested that allergic transfusion reactions could be induced by the transfer of food allergens. In such a case, a six year old boy with acute lymphoblastic leukaemia suffered an anaphylactic shock when receiving blood from a donor pool. The doctors treated his reaction with adrenaline, and the boy’s mother said he had suffered a similar reaction after eating peanuts at the age of 1, after which peanuts had been excluded from his diet. The doctors found that three of the five blood donors had eaten handfuls of peanuts the evening before giving blood.

The major peanut allergen Ara h 2, is extremely resistant to digestion because of a peptide, so the doctors investigated whether the peanut allergens ingested by the donors could have been transmitted in the transfusion. When the boy’s blood was tested it was found that peanut-specific antibodies were far higher than normal, as were the peptide levels. The patient was therefore found to be allergic not only to raw peanuts but also to the protein that ended up in the blood.

Lead author Dr Joannes F M Jacobs of Radboud University Nijmegen Medical Centre in the Netherlands says that such a case has never been documented in literature before. In another case, a woman with no allergies, who had received blood from a young man with a severe peanut allergy, developed an anaphylactic reaction within minutes of eating peanut butter. See this FM report for more. There has been a call for blood screening of the diets of potential blood donors, but this is thought to be expensive and impractical.

Source: The New England Journal of Medicine.

First published in May 2011

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