There is no evidence to suggest that nut allergens spread through aircraft ventilation systems, experts say

There is no evidence to support the commonly accepted view that nut allergens can be spread through aircraft ventilation systems, allergy and aviation medicine specialists say in an evidence review published in the US newspaper The Guardian. Archives of diseases in childhood.

Allergen residue on surfaces, such as tray tables and seatback video screens, poses the greatest risk – a risk likely magnified by the fast turnaround times of many low-cost airlines, they suggest.

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 due to passengers with food allergies taking more precautions when flying, they acknowledge.

About 2-3% of children and 1-2% of adults in Britain have a food allergy, the authors say. And similar figures are observed in middle-to-high-income countries. Food allergy is the most common cause of anaphylaxis, a potentially life-threatening allergic reaction.

In an attempt to dispel some misconceptions about the perceived risks to passengers with food allergies on commercial flights, the authors drew on the 1980 systematic review of published evidence commissioned by the UK Civil Aviation Authority (CAA). 2023.

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

Although peanut allergens can be detected at very low levels in the air when shelling nuts, the dust settles quickly and can only be detected in very close proximity to the nuts, implying that there is very little dust circulating in the air .

Additionally, aircraft cabin ventilation systems are designed to circulate air throughout the aircraft, rather than along the cabin, minimizing the chance of passenger-generated contaminants spreading throughout the cabin, the authors explain.

During a flight, air is completely exchanged every three to four minutes. This is comparable to every 10 minutes for hospitals and classrooms. In modern large commercial aircraft, approximately half of the air intake consists of recirculated air that has passed through particulate air filters that effectively remove dust, fumes and microbes while capturing aerosolized food particles. The other half comes from outside.

Food proteins are often ‘sticky’ and any accidental exposure is likely to result from surface contamination on chairs, seat-back entertainment systems and tray tables. This can be transferred from the hands to the food being eaten 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, especially on low-cost airlines,” the authors point out.

Pre-boarding food-allergic passengers may be helpful 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 consume nuts during the flight are unlikely to reduce the risk of in-flight reactions and may provide false reassurance, they add.

Although many passengers with food allergies prefer to bring their own food, when inflight meal service is offered, most airlines offer allergen-free options if requested in advance.

And passengers at risk of food anaphylaxis should carry adrenaline [epinephrine] auto-injectors, such as an EpiPen, in their carry-on luggage, as these are not always included in on-board medical kits, nor are cabin crew always allowed to use them, the authors advise.

“There is no evidence that peanut or tree nut allergens are spread through aircraft cabin ventilation systems. Rather, the main risks are due to failure to avoid dietary habits, or to allergen residues on surfaces, which can then be transmitted through touch – a situation that is getting worse.” due to the very short lead times with many low-cost airlines,” the authors conclude.

“Airlines should have a clear policy regarding food allergies, which is easily available through their websites or upon request. This policy must be applied consistently by both ground and cabin crew to provide reassurance to food-allergic passengers and their caregivers.” they add.