No evidence to suggest nut allergens spread through airplane ventilation systems, experts say

There is no evidence to support the widely held belief that nut allergens can be spread through airplane ventilation systems, allergy and aviation medicine specialists say in a review of the evidence published in the Archives of childhood illnesses.

Allergen residue on surfaces, such as table tops and file video screens, is the main risk, a risk that is likely heightened by the fast turnaround times deployed by many low-cost carriers, suggest -they.

And allergic reactions to food are about 10 to 100 times less common during flights than on the ground, they point out, although this could be because passengers with food allergies take more precautions when flying , they recognize.

In the UK, around 2-3% of children and 1-2% of adults have food allergies, the authors say. And similar rates are seen in middle- and high-income countries. Food allergy is the most common cause of anaphylaxis, a life-threatening allergic reaction.

In an effort to clear up some misconceptions about the perceived risks to passengers with food allergies on commercial flights, the authors drew on the systematic review of published evidence dating back to 1980, commissioned by the Food and Drug Administration Civil Aviation Authority (CAA) of the United Kingdom in 2023.

With the notable exception of fish/seafood fumes and exposure to occupational wheat flour, allergic reactions to aerosolized foods are rare and rarely reproducible, the authors say.

While peanut allergens can be detected at very low levels in the air when shelling nuts, dust settles quickly and can only be detected in close proximity to the nuts, meaning very little dust circulates in the air.

Additionally, aircraft cabin ventilation systems are designed to circulate air through the aircraft rather than along the cabin, minimizing the risk of spreading passenger-generated contaminants into the cabin, explains the authors.

The air is completely renewed every three to four minutes during a flight. This compares to every 10 minutes in hospitals and classrooms. In large modern commercial aircraft, about half of the incoming air is recirculated air that has passed through particulate filters that effectively remove dust, fumes and microbes and at the same time capture aerosolized food particles. The other half comes from outside.

Food proteins are often “sticky” and any unintended exposure is likely from surface contamination on seats, seat-back entertainment systems, and table tops. This could be transferred from the hands to the food consumed or directly to the mouth and/or face.

Cleaning these surfaces at the start of a flight with disinfectant wipes will minimize this risk, and is “particularly important, given the minimal cabin cleaning that often takes place between flights, particularly with low-cost airlines”, emphasize the authors.

Allowing passengers with food allergies to pre-board could help in this regard, say the authors, who note that the U.S. Department of Transportation already requires airlines to allow passengers with nut allergies to do so.

But announcements asking passengers not to eat nuts during the flight are unlikely to reduce the risk of reactions on board and could provide false reassurance, they add.

While many passengers with food allergies prefer to bring their own food, where an inflight meal service is provided, most airlines offer allergen-free options upon prior request.

And passengers at risk of food anaphylaxis should carry adrenaline (epinephrine) auto-injectors, such as an EpiPen, in their carry-on baggage, as they are not always included in on-board medical kits, and staff cabin attendants are not always allowed to use them, advises the authors.

“There is no evidence that peanut or tree nut allergens are spread through airplane cabin ventilation systems. Rather, the main risks are due to either failure of food avoidance measures or the presence of allergen residues on surfaces, which can then be transferred by touch – an exacerbated situation.” by the very short turnaround times of many low-cost carriers,” the authors conclude.

“Airlines should have clear policies regarding food allergies, easily accessible on their websites or upon request. These policies should be applied consistently by ground and cabin crew, to reassure passengers suffering from allergies. “food allergies and their caregivers.” they add.