-- Shortly after boarding a flight, Sydney Silverman, 13, equipped with her own disinfecting wipes, takes a moment to vigilantly wipe down her seat and the seats next to her. Every stitch, tray table, pocket and armrest must be tended to.
Sydney has practiced this routine for years, taking over her parents' duties once she got older, according to her father, Dr. Michael Silverman, a psychologist in New York City.
No, the Silvermans are not germaphobes. Sydney suffers from a severe peanut allergy and the consequences of coming into contact with the allergens can be life threatening.
The policies between airlines are inconsistent, and within those policies, the actual practices of the flight crews and gate agents can vary even more.
According to her father, Sydney has been embarrassed by gate agents and kicked out of restaurants by staff multiple times after disclosing her allergy.
Sydney has designed her own personal information cards, like business cards. She carries them around and offers them to restaurant staff. The cards introduce herself, and her allergy. The vast majority of reactions are enthusiastic, according to her father. Sometimes the chef will personally come out and explain exactly how he will prepare her food.
Other times, they are curtly asked to leave the restaurant.
But one January flight home on Delta Air Lines from a family vacation in Florida was different, according to Silverman.
A flight attendant observed Sydney cleaning the seat and asked if she was allergic to peanuts. She said yes. The flight attendant asked Sydney if she would like an announcement to be made. The girl responded that she's usually OK.
"Because she's aware of the sort of response that you get," her father said, referring to the past experiences of being ostracized.
But the flight attendant made the announcement anyway and told Sydney she would not serve peanuts on the flight. The flight crew also asked those in the rows around Sydney to refrain from eating any peanuts.
"Somebody was actually watching out for her," said Silverman.
But no two experiences are the same.
When Laura Ilsley of Travis, California, booked her flight with Delta Air Lines for last April, she was assured a note was left in the reservation indicating her 4-year-old daughter has a severe peanut allergy.
"Having our daughter suffer from an anaphylactic reaction on a plane was not an option," Ilsley told ABC News.
The Ilsley family was traveling back to the United States from Turkey, where the father was based with the U.S. military.
When they arrived at the airport however, they were informed their flight was overbooked and they would be flying with Air France.
When Ilsley informed the French airline of her daughter's medical condition, the flight crew refused to make an announcement or adjust their plans to serve peanuts. Air France told Ilsley her family was not welcome on the flight, she said.
Air France did not immediately respond to ABC News' request for comment. The airline previously responded to the incident with a statement, as reported by The New York Times, "[Air France] determined it was not in the best interest of the passenger to board the flight on such short notice.”
The statement continued: "The case was handled with concern for passenger safety as the top priority.”
The Ilsley family were rebooked on another Delta flight, where they were allowed to pre-board to clean their seating area. The Delta flight crew additionally made an announcement asking passengers to refrain from eating peanuts on the flight.
Dora Leah Govorko, a teenager from New Jersey, told ABC News she and her brother went to find their seats on a 2013 Virgin Atlantic flight while their mother, Ana Govorko, went to speak to the crew about Dora's severe peanut allergy.
When Dora's mother returned, the crew asked if the mother had documentation of her daughter's previous reactions and a doctor's note allowing her to fly. Dora had a doctor's note, but no history readily available. During a brief argument with the crew, Dora's eye began itch and redden, which raised panic among the flight crew.
During the deliberations, Dora says she nearly began to cry after hearing a passenger express their disdain for the episode. "Why don't they just take them off the plane already?" she said she heard.
"It hurts to hear people say these things about you when you know you can't control these problems," Dora told ABC News. "Even when you would really want to."
After Dora's inexplicable symptoms subsided, the Virgin crew eventually allowed the family to fly.
Meals and snacks provided on U.K.-based airline's flights do not contain peanuts, but the meals are not produced in nut-free environments, so they could contain traces of allergens. As other airlines frequently remind passengers, Virgin cannot stop other customers from bringing their own food on board, so it is impossible for to guarantee that the airplane will be nut-free. On their website, the Virgin asks passengers to inform the airline of their allergies before traveling, in which case they will make an announcement and ask passengers around them to refrain from eating or opening that item.
Although Virgin says they last updated their nut policy in December of 2016, it is unclear what specifically is different.
Those with nut allergies have formed a community in the age of social media and easy communication. Thousands of families affected by the condition share stories, both good and bad, with each other, in an effort to safer navigate a nut-filled world where policies and practices are remarkably inconsistent, exacerbating the problem.
They know which airlines and schools are friendly to their needs, and which are less so.
The country's largest airline is notorious among the nut allergy community. While American Airlines does not serve peanuts, they, as a matter of policy, do not let passengers with nut allergies pre-board to sanitize their seating area, make "buffer zones," nor will they ask passengers to refrain from eating peanuts. American's online policy says allowing such passengers to pre-board "can create a false sense of security and doesn't eliminate risk."
United Airlines also does not serve peanuts on their flights, but when requested, will ask surrounding passenger to not open or eat any peanut products.
The Chicago-based airline did not immediately respond when asked if they allow those with peanut allergies to pre-board.
Annecdotally, Delta Air Lines, JetBlue and Southwest Airlines seem to be the most popular airlines among nut-free travelers.
JetBlue does not serve any kind of nuts on board their aircraft and when requested, will create a buffer zone one row in front of and one row behind the allergic customer. They will not make any announcements, however.
When Southwest Airlines is made aware of a peanut allergy, the airline will serve alternative snacks on flights throughout the customer's itinerary and provide them with a document to present to the flight attendant when boarding, in order ensure the crew is aware.
While they might be accommodating now, Southwest was, in fact, the first to exclusively serve peanuts on flights back when full meals and onboard kitchens were the norm on other airlines.
The budget carrier took ownership of the cost-cutting feature, marketing itself as the "peanut airline." The legume served as an alternative to meals, keeping fares low and flights full. Other carriers would soon follow suit, until 2011 when peanuts were largely eliminated from the pantry of major airlines.
The Americans With Disabilities Act does not apply to passengers on an aircraft. So in 1986, Congress passed the Air Carrier Access Act. Under ACAA, the Department of Transportation does not generally consider an allergy to be a disability, however "if a person’s allergy is sufficiently severe to substantially limit a major life activity, then that person meets the definition of an individual with a disability," a DOT spokesperson told ABC News.
DOT defines an individual with a disability as someone who has an impairment that substantially limits their ability to care for themselves, perform manual tasks, walk, see, hear, speak, breath, learn or work.
This year, a nonprofit called Food Allergy Research & Education, or FARE, is taking on American Airlines over their policies facing those with food allergies.
In February, FARE filed a complaint with DOT asking the federal government to investigate the allegations that American is violating the Air Carrier Access Act by not allowing those with food allergies to pre-board the aircraft.
American Airlines' attorneys filed a response in March denying the assertion that they are required to allow those with food allergies to pre-board. American Airlines argued that passenger can wipe down their seating area without pre-boarding, and doing so does not "necessarily prevent a food allergic passenger from coming in contact with an allergen."
American's response also stated that allowing such passengers to pre-board adds a burden on the airline.
A DOT spokesperson told ABC News that they are looking into the matter and could not comment. A spokesperson for American Airlines declined to comment on the complaints.
The peanut industry has long lobbied to keep peanuts at 30,000 feet. The American Peanut Council has been fighting against claims that allergic passengers can be harmed by simply inhaling its dust. "Many [allergic individuals] simply do not believe the evidence and are very ready to offer contrary and passionate views based on personal or family experiences of nut reactions while on airplanes," said the National Peanut Council in a statement on their website.
"It is highly unlikely for a passenger to inhale nut protein from someone consuming nuts a few rows in front of him/her," said Dr. Matthew Greenhawt, a pediatric allergist at the University of Michigan, according to the council, which quoted Greenhawt.
However, FARE told ABC News that research shows allergic individuals can suffer reactions from inhaled dust particles.
According to the American Academy of Allergy, Asthma & Immunology, there have cases of individuals suffering allergic reactions from airborne particles.
The scientific community has not come to a clear consensus on the exact prevalence of tree nut and peanut allergies, largely because not everyone who reports a food allergy in fact has one.
However, some research has estimated it as more than 1 percent of the population, although a number of people outgrow the allergy, according to the American College of Allergy, Asthma & Immunology.
A 2010 study published in the Journal of Allergy and Clinical Immunology says the percentage of children with nut allergies more than tripled to 2.1 percent between 1997 and 2008. The reasons for the increase are unclear.
The worst danger food-allergic individuals face is anaphylaxis -- basically an inappropriate reaction of the immune system that can cause hives, swelling and other symptoms. These symptoms can become so severe that it blocks the airways, leading to suffocation.
Allergens can spread a number of ways. While the conventional route is ingestion, highly sensitive individuals can react to airborne particles, according to the American Academy of Allergy, Asthma & Immunology.
To combat the symptoms, most travelers with severe allergies to peanuts hand carry their medications at all times, including autoinjectable epinephrine.
While epinephrine has proven to be quite effective, it is not a perfect treatment. In any case, someone suffering from anaphylaxis needs professional medical care as soon as possible; making a plane a particularly dangerous place to suffer a severe episode.
Creating an airplane cabin free from allergens is an impossible task and no airline, no matter what steps they take to be accommodating, can guarantee the safety of a passenger with a severe food allergy.
There are however a number of steps one can take to lower their risk and make their traveling as smooth as possible.
The policies of major U.S. carriers can be found at the links below:
ABC News' Dan Childs contributed to this report.