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Tuesday, June 14, 2011
Q&A with Wayne Shreffler, MD, PhD
Due to the significant number of children who have peanut allergies, the U.S. Department of Transportation is considering steps to help make air travel safer for people with peanut allergies. The Department is considering three alternatives:
Wayne Shreffler, MD, PhD, is a pediatric allergist at MassGeneral Hospital for Children and director of the Food Allergy Center at Massachusetts General Hospital. His research focuses on food allergy and asthma.
Q: For kids who are allergic, what's the risk in having peanuts on commercial flights and are they greater than in everyday life?
A: Children with peanut allergy and their families live with the everyday risk of an accidental exposure and most learn very well how to manage that risk by both avoidance and available treatment. Far and away, the risk of exposure that people need to mitigate against is ingestion. Contact with peanut on the skin or simply smelling peanut are not exposures that are very likely to lead to dangerous reactions. If, however, particulate matter [very small pieces] from peanuts is inhaled, it can lead to a dangerous reaction.
So, one of the concerns with peanuts on flights is that there is a plausibly increased risk of inhalation reactions due to the small space and conditions in the cabin. The other concern is that should a severe reaction occur in flight, medical attention might be delayed.
Q: What's the science behind this?
A: Studies involving the intentional exposure to highly allergic subjects have shown that the risk of life threatening reactions from skin contact or smell (the detection of very small organic molecules, not the proteins that cause allergic reactions) is very low. However, trace contamination of hands or food leading to unintentional ingestion or a curious child picking up a bit of a peanut kernel and putting it in his or her mouth are real risks.
In the National Registry of Peanut and Tree Nut Allergy, 62 of 3704 (>1.5%) participants indicated that they had experienced a reaction on a plane, and of the 48 who were directly contacted, 42 reported that the exposure occurred on the plane. Thirty-five of these reacted to peanut and 7 to tree nuts. Twenty indicated that they were exposed by ingestion, 14 by inhalation and 8 by contact. The most severe reactions were from ingestions, followed by inhalation. The large majority of reactions were from an item served by the airline.
Q: The danger of accidental consumption of whole peanuts (particularly if they're packaged) seems low compared, for example, to food that might include nuts as an ingredient or that's processed in a facility that also processes nuts. Can you comment on that?
A: That is probably true. Most unintentional ingestions are from peanut-containing foods, rather than to peanuts. However, some factors specific to air travel (e.g. the apparent increased risk of inhalation reactions) may be unique.
Q: What are the most common causes of accidental reactions to food allergens?
A: The most common reactions occur to the most common allergens: milk, egg, wheat, soy, peanut, tree nuts, shellfish and fish. Peanuts and tree nuts have been disproportionately linked to more severe allergic reactions.
Q: What about the danger of an allergic toddler picking up a nut that's fallen onto the floor or into a seat cushion?
A: For a significant proportion of individuals with peanut allergy, even a very small fragment is sufficient to provoke a major reaction.
Q: Is a total ban necessary or would a "buffer zone" work as well? Many schools have peanut-free tables in their cafeterias now.
A: A buffer zone would likely reduce the frequency of ingestion and contact reactions if the cabin was properly cleaned between flights. There may also be ways to mitigate the risk of inhalation reactions (e.g. HEPA filter of recirculating air, packages that minimize the aerosolization of particles, but given that a third of reactions were by inhalation, failing to address that would be inadequate.
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