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Reactions to peanut during air travel: can anaphylaxis be due to inhalation?


Reviewed: 2/20/20
Can the aroma of peanut from passengers eating peanut on a plane cause anaphylaxis in a peanut allergic passenger?


Editor’s note: the answer to this questions has been updated to reflect the most recent data.

For those with peanut allergy, there has been a persistent concern about the risk of having a reaction from casual exposure to peanuts while on an airplane. Specific concerns have been raised about reported airborne reactions from inhaling peanut dust or peanut butter vapors or aroma, from being in close proximity to peanuts, or from coming into contact with contaminated surfaces. This is understandable. However, the peanut allergic flier should rest assured that since the issue was first studied in 2004, data have consistently shown that peanut dust does not become airborne nor does inhaling peanut butter vapors provoke a reaction, that skin contact with either form of peanut is unlikely to cause any reaction beyond local irritation that can be washed off, and lastly that surfaces (including hands) that become contaminated with peanut can be easily washed off. Let’s briefly summarize this evidence.

A 2004 study by Simonte et al. exposed 29 severely peanut allergic patients to a double-blind inhalation challenge to 3oz of peanut butter (or soy butter, both masked for smell) just 12 inches from the nose. As well, a pea sized drop of either masked butter was smeared on the skin for 1 minute, and then was removed. In both exposures, no one developed any allergic reactions. There were 3 patients who developed localized erythema and 5 developing localized pruritus from the peanut butter skin contact, but 5 also developed erythema with soy butter skin contact, which demonstrates that butters on the skin can cause irritation but not generalized reactions. The authors concluded that casual contact or inhalation of peanut butter was highly unlikely to cause any symptoms.

Also, in 2004, Perry et al. further investigated how effectively 5ml of smeared peanut butter could be abated from tabletops, counters, desks, water fountains, and from one’s hand; and if peanut dust from deshelling peanuts and then walking on their shells could be detected in the air. They noted that multiple commercial agents such as Formula 409, Lysol and Target brand cleaner (containing bleach) removed peanut from surfaces, and Tidy-Types wipes, Wet Ones, and both liquid and bar soap removed peanut from hands. This study also importantly showed that alcohol-based hand sanitizers did not remove peanut from hands, an important staple of how we advise patients. Most importantly, no airborne peanut was detected in filters worn at the level of the neck from the deshelling experiments. Investigators concluded that peanut can be abated from surfaces with multiple agents, and that peanut dust likely doesn’t circulate in the air.

In 2013, baseline work by the LEAP team as part of home monitoring for compliance with their trial further replicated the findings of both Simonte and Perry. Brough et al. noted that peanut smeared laminate and wood tables vigorously cleaned with a standard commercial cleaning detergent held levels of peanut just above the assay’s detectable threshold (<0.2ug), but that granite surfaces had undetectable levels. Airborne exposure was tested above active and just-halted shelling as well as above baked and pan cooked products. They noted that at 1cm and 1m above peanut being actively shelled, 331ug/m3 and 4.7ug/m3 peanut was detected (assay lower limit of detection being 2.5ug), respectively, but as soon as the shelling was ceased no residual levels were noted at either height. Thus, these data show that if you put a probe right over someone shelling peanut, a small amount of dust can naturally be detected, but within a few feet only a few nanograms were detectable, likely attributable to the highly sensitive nature of the detecting probe. These became immediately undetectable once the shelling stopped, and investigators concluded that it is highly unlikely that peanut particles remain in the air after shelling.

In 2016, Jin et al re-replicated these findings within a cabin of an airplane in flight. They noted surface contamination of Ara h 2 on unwashed tray tables after someone ate peanut over them, and among 7 air filters measuring Ara h 2 content when placed on a tray table directly below the mouth of someone eating peanut only 1 filter detected any level, which was 1-2ng/500cm3. They found no detectable peanut levels from 3 air filters tested in a restaurant where individuals were deshelling and eating peanut. Investigators concluded that the risk of exposure to peanut on an airplane stems from potentially contaminated surfaces and not from airborne levels.

Putting the aggregate of these data into perspective would imply that peanut products likely could be detected on a tray table, common surface, seat, and on the floors if these areas are not cleaned but that there is an exceptionally low likelihood of any airborne circulation. Caution is also needed to rectify what the significance of a few nanograms of detectable protein means - these probes used by Brough and Jin are highly sensitive and can detect exceptionally miniscule amounts. However, these levels are well below any known or theorized level that would be likely to affect even the most highly sensitive patient. Three recent studies have shown that less than 5% of the peanut allergic subjects develop objective symptoms to ingestion of less than 1.5-1.95mg of peanut protein: for reference 1 nanogram is 0.000001mg. The point here is not to focus on the evolution of more highly sensitive detection methods, but rather to address the more practical issue - that detection of increasingly minute quantities has no clinical relevance. More importantly, the main concern should be on the surface contamination and not airborne particulate. Tray tables and personal seating areas on an airplane should be wiped down, and a 2013 study noted that peanut allergic fliers who reported wiping down their tray tables had significantly lower odds of having reported an allergic reaction to peanut occurring in flight.  

It is difficult to understand the context of the reported airborne exposures noted in the 4 studies of self-reported airline reactions, including those addressed in our 2012 response to this question.  The limiting feature of these data is that the mechanism of these reactions was not validated by a medical provider, so there is no way to determine what exposure may have occurred, and how. This is not to be confused with their being doubt that a potential reaction occurred. The issue is more through what means, which in the context of this discussion makes all the difference.  Thus, these remain in the realm of anecdotal though concerning evidence, and they have been the incentive for the aforementioned studies of surface and air exposure.

The bottom line is that flying with a peanut allergy and being exposed to potential sources of peanut in the cabin is not likely to represent an increased risk to the peanut allergic flier. There is no evidence to support peanut vapor as a cause of reactions or that peanut dust itself circulates and causes reactions. There is evidence that common surfaces on an airplane may have residual peanut contamination, but there is also evidence that this can be readily cleaned with commercial agents that passengers can bring aboard themselves, and that doing such cleaning has been noted to reduce the risk of reporting an in-flight reaction.

1. Simonte SJ, Ma S, Mofidi S, Sicherer SH. Relevance of casual contact with peanut butter in children with peanut allergy. J Allergy Clin Immunol 2003;112:180-2.
2. Perry TT, Conover-Walker MK, Pomes A, Chapman MD, Wood RA. Distribution of peanut allergen in the environment. J Allergy Clin Immunol 2004;113:973-6.
3. Brough HA, Makinson K, Penagos M, et al. Distribution of peanut protein in the home environment. J Allergy Clin Immunol 2013;132:623-9.
4. Jin JJ, Dorn JM, Yunginger J, Ott NL.  Ara h 2 is detectable on surfaces of commercial airplanes. J Allergy Clin Immunol Pract. 2018 Jun 4. pii: S2213-2198(18)30349-0. doi: 10.1016/j.jaip.2018.05.027.
5. Blom WM, Vlieg-Boerstra BJ, Kruizinga AG, van der Heide S, Houben GF, Dubois AE. Threshold dose distributions for 5 major allergenic foods in children. J Allergy Clin Immunol 2013;131:172-9.
6. Blumchen K, Beder A, Beschorner J, et al. Modified oral food challenge used with sensitization biomarkers provides more real-life clinical thresholds for peanut allergy. J Allergy Clin Immunol 2014;134:390-8.
7. Ballmer-Weber BK, Fernandez-Rivas M, Beyer K, et al. How much is too much? Threshold dose distributions for 5 food allergens. J Allergy Clin Immunol 2015;135:964-71.
8. Hourihane JO, Allen KJ, Shreffler WG, et al. Peanut Allergen Threshold Study (PATS): Novel single-dose oral food challenge study to validate eliciting doses in children with peanut allergy. J Allergy Clin Immunol 2017;139:1583-90.
9. Sicherer SH, Furlong TJ, DeSimone J, Sampson HA. Self-reported allergic reactions to peanut on commercial airliners. J Allergy Clin Immunol 1999;104:186-9.
10. Greenhawt MJ, McMorris MS, Furlong TJ. Self-reported allergic reactions to peanut and tree nuts occurring on commercial airlines. J Allergy Clin Immunol 2009;124:598-9.
11. Comstock SS, DeMera R, Vega LC, et al. Allergic reactions to peanuts, tree nuts, and seeds aboard commercial airliners. Ann Allergy Asthma Immunol 2008;101:51-6.
12. Greenhawt M, MacGillivray F, Batty G, Said M, Weiss C. International study of risk-mitigating factors and in-flight allergic reactions to peanut and tree nut. J Allergy Clin Immunol Pract 2013;1:186-94.

Airline travel and food allergy
Q: 7/28/2012

Does the Academy have a position on advice to patients with peanut and tree nut allergy traveling on commercial airlines?

Do we have a position on how the airlines should handle these patients?

Is there hard data on in-flight reactions from airborne nut/peanut?

A: Thank you for your inquiry.

The Academy does not have a position paper on this particular topic. However, literature is available for patients, and there are studies investigating the occurrence of food allergy reactions during airline flight.

Below you will find the abstracts of these two articles, one from the Annals of Allergy, Asthma, and Immunology and the other from the Journal of Allergy and Clinical Immunology, dealing with the issue of allergic reactions to foods during an airline flight. In addition, there are two published commentaries on these articles. The references for these commentaries are:

Weiss C. Letter to the Editor. Commercial airlines and food allergy. Annals of Allergy, Asthma, and Immunology 2008 (November); 101(5):556-557.

James JM. Airline snack foods: tension in the peanut gallery. Journal of Allergy and Clinical Immunology 1999 (July); 104(1):25-27.

In addition, there is a general statement on air travel and children's health issues that has a section on allergic reactions during airline flight. This appeared in Pediatric Child Health. This article is available to you free of charge online. I have have provided a link to the article for your convenience.

Air travel and children’s health issues: Pediatric Child Health. 2007 January; 12(1): 45–50

Finally, there is excellent information available through the Food Allergy and Anaphylaxis Network (FAAN). Their website has an article entitled "Ten Tips for travelers with Allergy" and an article entitled "Flying with Food Allergy".

FAAN WEBSITE: Ten tips for travelers with allergy

FAAN WEBSITE: Flying with food allergy

Since a significant portion of these reactions occur by inhalation, I have also copied below an abstract on food hypersensitivity by inhalation (Ramirez) which was written for physicians and puts the issue of such reactions into perspective.

Thank you again for your inquiry and we hope this response is helpful to you.

Ann Allergy Asthma Immunol. 2008 Jul;101(1):51-6.
Allergic reactions to peanuts, tree nuts, and seeds aboard commercial airliners.
Comstock SS, DeMera R, Vega LC, Boren EJ, Deane S, Haapanen LA, Teuber SS.
Division of Rheumatology, Allergy, and Clinical Immunology, Department of Internal Medicine, University of California, Davis, School of Medicine, Davis, California, USA.
Background: Minimal data exist on the prevalence and characteristics of in-flight reactions to foods.
Objectives: To characterize reactions to foods experienced by passengers aboard commercial airplanes and to examine information about flying with a food allergy available from airlines.
Methods: Telephone questionnaires were administered to individuals in a peanut, tree nut, and seed allergy database who self-reported reactions aboard aircraft. Airlines were contacted to obtain information on food allergy policies.
Results: Forty-one of 471 individuals reported allergic reactions to food while on airplanes, including 4 reporting more than 1 reaction. Peanuts accounted for most of the reactions. Twenty-one individuals (51%) treated their reactions during flight. Only 12 individuals (29%) reported the reaction to a flight attendant. Six individuals went to an emergency department after landing, including 1 after a flight diversion. Airline personnel were notified of only 3 of these severe reactions. Comparison of information given to 3 different investigators by airline customer service representatives showed that inconsistencies regarding important information occurred, such as whether the airline regularly serves peanuts.
Conclusions: In this group of mainly adults with severe nut/seed allergy, approximately 9% reported experiencing an allergic reaction to food while on board an airplane. Some reactions were serious and potentially life-threatening. Individuals commonly did not inform airline personnel about their experiences. In addition, the quality of information about flying with food allergies available from customer service departments is highly variable and, in some cases, incomplete or inaccurate.

J Allergy Clin Immunol. 1999 Jul;104(1):186-9.
Self-reported allergic reactions to peanut on commercial airliners.
Sicherer SH, Furlong TJ, DeSimone J, Sampson HA.
Division of Pediatric Allergy/Immunology, Department of Pediatrics, Mount Sinai School of Medicine, New York, USA.
Background: Allergic reactions to food occurring on commercial airlines have not been systematically characterized.
Objective: We sought to describe the clinical characteristics of allergic reactions to peanuts on airplanes.
Methods: Participants in the National Registry of Peanut and Tree Nut Allergy who indicated an allergic reaction while on a commercial airliner were interviewed by telephone.
Results: Sixty-two of 3704 National Registry of Peanut and Tree Nut Allergy participants indicated a reaction on an airplane; 42 of 48 patients or parental surrogates contacted confirmed the reaction began on the airplane (median age of affected subject, 2 years; range, 6 months to 50 years). Of these, 35 reacted to peanuts (4 were uncertain of exposure) and 7 to tree nuts, although 3 of these 7 reacted to substances that may have also contained peanut. Exposures occurred by ingestion (20 subjects), skin contact (8 subjects), and inhalation (14 subjects). Reactions generally occurred within 10 minutes of exposure (32 of 42 subjects), and reaction severity correlated with exposure route (ingestion > inhalation > skin). The causal food was generally served by the airline (37 of 42 subjects). Medications were given in flight to 19 patients (epinephrine to 5) and to an additional 14 at landing/gate return (including epinephrine to 1 and intravenous medication to 2), totaling 79% treated. Flight crews were notified in 33% of reactions. During inhalation reactions as a result of peanut allergy, greater than 25 passengers were estimated to be eating peanuts at the time of the reaction. Initial symptoms generally involved the upper airway, with progression to the skin or further lower respiratory reactions (no gastrointestinal symptoms).
Conclusions: Allergic reactions to peanuts and tree nuts caused by accidental ingestion, skin contact, or inhalation occur during commercial flights, but airline personnel are usually not notified. Reactions can be severe, requiring medications, including epinephrine.

Clin Mol Allergy. 2009 Feb 20;7:4.
Food hypersensitivity by inhalation.
Ramirez DA Jr, Bahna SL.
Allergy & Immunology Section, Louisiana State University Health Science Center in Shreveport, 1501 Kings Highway, Shreveport, LA, USA.
Though not widely recognized, food hypersensitivity by inhalation can cause major morbidity in affected individuals. The exposure is usually more obvious and often substantial in occupational environments but frequently occurs in non-occupational settings, such as homes, schools, restaurants, grocery stores, and commercial flights. The exposure can be trivial, as in mere smelling or being in the vicinity of the food. The clinical manifestations can vary from a benign respiratory or cutaneous reaction to a systemic one that can be life-threatening. In addition to strict avoidance, such highly-sensitive subjects should carry self-injectable epinephrine and wear MedicAlert(R) identification. Asthma is a strong predisposing factor and should be well-controlled. It is of great significance that food inhalation can cause de novo sensitization.

Phil Lieberman, M.D.