Are Food Allergies Contagious?

Are Food Allergies Contagious?

People familiar with food allergies may roll their eyes at the question, and yet it is an undeniably common one: are food allergies contagious?

Fortunately, food allergies can’t be spread like the common cold. Your child can’t sneeze and “infect” his classmates with an allergy.

However, there is one odd and extremely rare way in which a food allergy can be passed from one person to another: via blood.

It’s in the Blood

There have been just a handful of reports of food allergies appearing in individuals after they receive blood transfusions or an organ donation. It is such a rare anomaly that many blood centers do not screen donors for food allergies. And yet some do; there appear to be no set guidelines regarding food allergies and blood donations.

Fortunately, because the cells responsible for the allergic reaction are not replenished by the individual’s immune system, food allergies transmitted this way are typically temporary.

8-Year-Old Canadian Boy Temporarily Allergic to Fish and Nuts

One example of the rare transfer of food allergies via blood transfusions is the case of an 8-year-old Canadian boy who received regular blood transfusions as part of his cancer treatment. He had no previous history of allergies, but a few weeks after his third transfusion, he had an anaphylactic reaction in response to eating salmon. He had eaten salmon approximately six weeks earlier without any adverse reaction whatsoever.

Unfortunately, his first anaphylactic reaction was followed by a milder allergic reaction just four days later, this time in response to peanuts. He had last eaten peanut butter without a problem approximately four weeks prior.

A blood test revealed IgE cells specific to peanut and salmon allergies. The child’s doctors suspected that the IgE cells, which are responsible for provoking allergic reactions, were transferred to him via the blood donations. The blood donors were tracked by the Canadian Blood Services, and sure enough, one donor was severely allergic to peanuts and salmon.

The boy’s parents were advised to cut peanuts and salmon out of his diet.

A follow-up blood test showed no remaining IgE cells, indicating that the allergies were temporary and not produced by the boy’s own immune system. He was able to revert back to an unrestricted diet.

In the meantime, the food-allergic blood donor was barred from future donations by the Canadian Blood Services.

Liver Transplant Acquired Food Allergy

The transference of a food allergy via liver transplant is now recognized well enough to have its own name: Liver Transplant Acquired Food Allergy, or LTAFA. It is apparently more common for children to develop food allergies after receiving liver tissues than for adults, even if two individuals share the same tissue source.

Allergic reactions are also reportedly three times higher in the first year after the transplant, and the risk falls in subsequent years.

So, are food allergies contagious? Not in the traditional sense. And in the event of acquiring a food allergy via a blood transfusion or liver transplant, the allergy might actually be temporary.

Talk to your child’s doctor about any concerns you may have, but know that the risk for developing a food allergy after either procedure is low. It may also be impossible for doctors to screen donors for allergies, depending on the circumstances under which the material is donated.

Have you ever been told you couldn’t donate blood because of a food allergy? Do you have any related anecdotes to share? Share your experiences in the comments below!


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