Peanut Particles Highest on Restaurant Surfaces

People with peanut and tree nut allergies may not need to worry very much about inhaling airborne peanut particles, new research suggests.

Instead, exposure is most likely through contact with a surface, like a table or a wall, in a restaurant or ice cream shop that serves peanuts, according to findings presented March 6th at the annual meeting of the American Academy of Allergy, Asthma and Immunology, Los Angeles, Calif.

“This may come as a surprise to some very sensitive peanut allergic individuals who feel that they have had reactions just by breathing in peanut dust. However, this research shows that the surfaces in those locations harbor more peanut allergens than the air,” Dr. Jay Jin, who led the study at Mayo Clinic in Rochester, Minnesota, told Reuters Health by email.

Dr. Jin and his team collected air samples and wiped surfaces in public places to measure levels of one of the common allergens in peanuts, the protein Ara h2.

As expected, the researchers found the highest levels of Ara h2 in areas with peanuts.

Table surfaces in restaurants where people were shelling peanuts had an average of 41.1 nanograms (ng) per milliliter (mL), while tables in restaurants without unshelled peanuts had only 0.77 ng per mL.

The tray tables on peanut-free airplanes had 13.5 ng per mL of Ara h2, while the tables on flights on which peanuts had just been served had 175.3 ng per mL of the allergen.

Library tables, places where peanuts are not commonly found, had an average of 0.75 ng per mL of Ara h2. The toppings counter in a frozen yogurt shop, however, had 11,126.7 ng per mL, the researchers found.

But even in areas where there are peanuts, Ara h2 concentrations in the air were low. A 15L-per-minute air sampler running for 15 minutes found 1.4 ng per mL of Ara h2 in restaurants where people were shelling peanuts. And no particles were detected in 5 liter-per-minute personal breathing zone samplers running for one hour in restaurants with no unshelled peanuts in the dining area.

“What is surprising about these findings is that avoidance of peanut allergen even in places where peanuts are not being served is virtually impossible. This suggests that peanut is a very ‘sticky allergen.’ However, the levels detected are very low, which is reassuring,” says Katrina Allen, director of the Center of Food and Allergy Research at the Murdoch Children’s Research Institute at the Royal Children’s Hospital in Parkville, Australia, who was not involved in the study.