It’s a belief that has led to the popular snack being banned on many airlines.
But it turns out there is no evidence that nut allergens can spread through aircraft ventilation systems, a scientific study has found.
Announcements asking passengers not to consume nuts during flights are unlikely to reduce the risk of in-flight reactions and may provide false reassurance, they found.
Instead, residue left on surfaces – such as tray tables and seatback video screens – poses the greatest risk to those passengers.
This risk is exacerbated by the rapid turnaround of budget airlines, but could be mitigated by a rapid phase-out, they suggest, with anyone with a nut allergy allowed to board early.
Announcements asking passengers not to consume nuts during flights are unlikely to reduce the risk of in-flight reactions and may provide false reassurance, the review suggested
Even then, the risk of allergic reactions to food during flights is up to 100 times less than when ‘on the ground’, although this may be a result of passengers taking precautions.
Food allergy is the most common cause of anaphylaxis, a potentially life-threatening allergic reaction.
It is estimated that around 2 to 3 percent of children and 1 to 2 percent of adults in Britain have a food allergy.
Researchers from Imperial College London conducted a systematic review of published evidence dating back to 1980 on behalf of the UK Civil Aviation Authority (CAA).
Although peanut allergens can be detected at very low levels in the air when shelling nuts, the dust settles quickly and very little dust circulates in the air.
Cabin ventilation systems are designed to circulate air throughout the aircraft, rather than along the cabin, so that the potential for passenger-generated contaminants to spread throughout the cabin is minimized, the authors said.
Peanut residue left on surfaces – such as tray tables and seatback video screens – poses the greatest risk to those passengers
During a flight, air is completely exchanged every three to four minutes, compared to every ten minutes for hospitals and classrooms.
In modern 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 sources, the authors explain, with allergic reactions to aerosolized foods rare.
Food proteins are often ‘sticky’ and any accidental exposure is likely to result from surface contamination, according to the findings published in the Archives of Disease in Childhood.
This can be transferred from the hands to the food being eaten or directly to the mouth or face.
Cleaning these surfaces at the start of a flight with sanitizing 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.’
Paul Turner, a clinical professor of anaphylaxis, childhood allergy and clinical immunity, at Imperial College London, who led the study, said the findings should reassure passengers.
He said: ‘People should not worry about airborne food transmission when they fly.
‘We have not found any evidence that nut particles can penetrate the cabin ventilation system of aircraft and cause reactions.’
He added: “The only thing people need to do to protect themselves is to clean their seating area.
‘If food-allergic people can board first and have time to clean their seating area with, for example, a baby wipe or an antibacterial wipe, they are much less likely to have unintended reactions.’
Researchers suggest that people at risk should carry adrenaline auto-injectors, such as an EpiPen, in their carry-on luggage, as these are not always included in on-board medical kits.
The report is being presented to major airlines, patient groups and anaphylaxis charities in a bid to get consistent policies for airlines operating from Britain and internationally ‘to reflect what the evidence is and make a real difference to food allergic passengers.’
Simon Williams, CEO of Anaphylaxis UK, said: ‘An important take-home message is that it is important that passengers clean their seating area, including the tray table and seat-back entertainment system.’