Not so for an eight-year-old boy who received a blood transfusion unexpectedly brimming with antibodies against salmon and peanuts—two foods he had routinely consumed in the past. A few weeks after receiving a blood transfusion, he experienced a severe allergic reaction called anaphylaxis within 10 minutes of eating salmon, according to the report, published online today (April 7) in the Canadian Medical Association Journal. “Allergies are so common in the population so we would anticipate that the rate of such events might be higher, and yet they have only been documented a few times in the literature,” says Julia Upton, an allergist at the Hospital for Sick Children in Toronto who wrote about this incident in the Canadian Medical Association Journal. However, because the boy's body itself did not make such antibodies against fish and nuts, his doctors said they suspected his allergies would go away within a few months. Although transfusion-borne allergies are not unheard of, they are extremely rare. With this case, Canadian Blood Services officials traced the problematic blood product back to a donor with several allergies, checked to see if any more of that person’s blood was in the donor pool (it was not) and barred that person from making future donations. “We’ve had two such cases reported to Canadian Blood Services in the past decade, and we distribute over a million blood components for transfusion every year,” says Robert Skeate, Canadian Blood Services’ associate medical director for eastern Canada. Some people with high levels of immunoglobulin E don't have allergies, and others with low levels of the protein do, she said. "I think it's hard to make sweeping recommendations based on one case report," Upton said.
– An 8-year-old boy in Canada never had any problems eating salmon or peanuts. Then, within just a few weeks of getting a blood transfusion as part of his treatment for brain cancer, he ate salmon and experienced a severe allergic reaction within 10 minutes. The same thing happened when he ate a chocolate peanut butter cup four days later. Doctors determined he was suffering from transfusion-borne allergies, and wrote about it in the Canadian Medical Association Journal. A piece in Scientific American calls the case "extremely rare." But with allergies so common, why is that, well, the case? Such a reaction can only occur if three factors are in place, explains Scientific American. The donor must first have high levels of the type of immunoglobulin-E (IgE) antibodies that set off allergic reactions. The patient must then receive a significant amount of that blood and, within a few months, be exposed to the allergen the IgE antibodies would react to. That's because—in good news for this 8-year-old and others like him—the IgE antibodies eventually disappear from the blood because the recipients don't produce the same antibodies on their own. In this case, the boy was again eating fish and peanut butter six months later. Scientific American points out that antibody-transfer is usually a good thing, as it helps guard against infection. And avoiding a situation like this is tough, LiveScience reports. Having allergies doesn't disqualify would-be donors (in either the US or Canada), and having a high level of IgE in the blood doesn't always correlate with experiencing allergies. (Last year, a toddler almost died from a nearly unheard-of allergy.)