Despite fears the mere presence of a peanut on a plane could inflame allergies, a Transportation Ministry inquiry has found "limited risk" anything other than actually ingesting a nut will cause an anaphylactic reaction.
The probe, quietly released last month, recommends continuing with measures like in-flight allergic buffer zones because of the "serious health implications" in the event of a reaction.
But the report says it's "noteworthy" that none of the airlines consulted reported any anaphylactic incidents due to peanut, nut or sesame seed allergies.
And an expert says he's only aware of one incident in the U.K ever to have been reported.
"Based on the information provided by the experts, it is clear that there is little to no evidence that there is a risk of anaphylaxis due to inhalation of or dermal contact with peanut, nut or sesame seed allergens," the inquiry says.
"Rather, any risk of a serious allergic reaction that might exist would be as a result of accidental ingestion."
'General public concern' about peanuts
Former Conservative transportation minister Lisa Raitt directed the Canadian Transportation Agency to look into passenger allergies to nuts in 2015 following directives released in response to a series of passenger complaints.
At present, the agency recommends a buffer zone consisting of the row of seats holding an allergic passenger, an announcement to other passengers in the zone to refrain from eating nuts and advising allergic passengers to carry their allergy medication and wipe down their seats.
The inquiry consisted of two expert reports and a round of consultations with airline carriers and allergy associations with a view to look at the risk of a reaction due to inhalation, skin contact or ingestion, and the effectiveness of existing measures to mitigate risk.
The risk analysis report was prepared by University of Colorado allergist and immunologist Dr. Matthew Greenhawt.
He says that while there is "general public concern" about the risks of inhalation or exposure through residue, the small number of studies that exist don't support the fear.
"The data that does exist has consistently shown that: a) peanut dust does not aerosolize; b) peanut butter contains no protein in its vapours; and c) surfaces can be effectively cleaned of any allergic residue and, moreover, there is minimal risk of anything more than a local irritation reaction from casual skin contact with the allergen," the inquiry says.
Necessity 'highly questionable'
Greenhawt cites a study done in 2004 which was "unable to detect any circulating airborne allergen particles on filters worn at the level of the patient's neck after 15 bags of whole peanuts were shelled and then walked on in a small room, both with and without air ventilation."
Another study involved 29 participants with severe peanut allergies who were subjected to three ounces of peanut butter held 12 inches away from their noses. Researchers also smeared a small amount of peanut butter on their skin.
None of them had respiratory symptoms or systemic allergic reactions. But three patients developed localized redness on their skin.
Greenhawt suggested the main benefit of buffer zones is in providing "comfort and psychological accommodation" to allergic passengers. Especially given the fact that passengers have to walk in and out of them to get to the bathroom.
"As it currently stands, given the dynamics of cabin airflow, the lack of evidence that peanut aerosolizes, and the evidence that surface wiping as abatement is highly effective, Dr. Greenhawt strongly encourages that the requirement be re-evaluated for evidence of necessity, 'which given present evidence would be highly questionable,'" the inquiry says.
"Finally, Dr. Greenhawt recommends that if the buffer zone does not provide any level of protection, the requirement imposed on Air Canada should be abandoned so as to not provide any misleading sense of security."
'Starting point for reducing the risks'
The airlines which were consulted said they had received only a handful of complaints in relation to the existing measures, including one from a passenger who expected a physical barrier around a barrier zone, and another involving a passenger who started to hyperventilate when a nearby passenger took out a peanut butter sandwich.
The inquiry also consulted the Canadian Society of Allergy and Clinical Immunology, Allergies Quebec, Food Allergy Canada and the Canadian Anaphylaxis Initiative.
Both Allergies Quebec and Food Allergy Canada said the existing measures should be a "starting point for reducing the risks for passengers with food allergies."
The anaphylaxis institute said it's not looking for peanut-free flights, but doesn't think the existing measures are adequate, given the difficulty in finding medical care in-flight.