There's a reason flying is making you sick. Here's how to avoid it.

Studies have shown that more than one in five people who travel on planes suffer from a cold or the flu after the flight. So what’s the cause of this post-flight sickness? And how can we avoid getting sick when we fly?

Here is the Skyscanner Australia guide to staying healthy when flying.

Apart from a severe bout of turbulence, or a cabin packed with crying babies, there’s nothing more disconcerting than sitting close to someone on a plane who insists on sniffing or who can’t stop sneezing. You can almost see the microbes coming your way.

Bacteria on planes.

Many people insist that airplanes are plagued with bacteria and viruses that are out to get them. They are on the armrests, in the seat pockets, all over the magazines, lurking in the toilet cubicles, and hovering in the air, ready to pounce. And, to some extent, they are right.

Microbiologists have tested planes and found that germs are commonplace, and can survive for hours or days after the passenger who brought them on board has departed.

Some of the 200 or so viruses that can cause the common cold can infect people for up to 18 hours after they have left the body, and flu viruses can infect people for up to eight hours after being let loose.

As well as causing the common cold and influenza, these bugs and viruses can cause everything from skin diseases and upset stomachs. Studies have found MRSA and E. Coli can live on the plane for over a week.

Where are the dirtiest places on a plane?

• • Tray table
  • Overhead air vents
  • Toilet flush buttons
  • Seatbelt buckles

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How germs and bacteria can spread on planes.

Modern planes typically use a combination of fresh and recirculated air, and some people believe that a plane’s air-conditioning system can help spread germs. But research suggests that this is not true.

A 2013 report conducted for the Federal Aviation Administration in the US concluded that while fresh air is germ-free at high altitudes, aircraft HEPA filters effectively remove bacteria and viruses, as well as dust and fungi.

However, there could be a greater risk of exposure when the aircraft is parked at the gate,when auxiliary power units generally provide ventilation rather than the aircraft’s own system. This helps germs to spread through the cabin more easily.

Another culprit could be the low relative humidity of cabin air. The typical relative humidity on planes is around 11 per cent. Some research suggests that low humidity interrupts the Mucociliary Clearance System, which consists of a thin layer of mucus and tiny hairs in the nose. This protective system traps viruses and bacteria and moves them from the nose to the throat, where they are swallowed and destroyed by acid in the stomach.

Because this system no longer works properly, bacteria and viruses get easier access to your lungs.
Either way, you certainly run the risk of becoming sick on a flight from directly inhaling particles in the air from someone’s coughing or sneezing. You can also become sick if you touch an infected surface and then touch your eyes, mouth or nasal passages.

The longer you are exposed to these things the more chance you have of getting ill. So, theoretically at least, you are less likely to get sick on shorter flights than long haul flights.

More facts about travel illness.

Because you are often around people from many different countries when you fly (and when you are in airports) it’s also possible that you might also be exposed to strains of virus that your body hasn’t come into contact with before. Without having acquired immunity to that particular strain you are more likely to get ill.

However, the bottom line is that almost anything that has come into contact with another human can cause illness, and places that are crowded are more likely to be awash with germs.

You can become infected on the train or in the taxi to the airport, or in the airport itself. Surfaces in airports, such as escalator railings, drinking fountains, and ATMs can all be contaminated. However, regular cleaning and air conditioning filtration could mean that airports are less contaminated than other crowded places.

How to stay healthy on a flight.

Short of wallowing in your own body-size plastic bubble with independent oxygen supply, there seems no way to avoid getting sick while travelling on a plane. Or is there?
If someone who is ill sneezes directly into your face then you can probably start counting the days to when you come down with something. But if you take some precautions you might have a chance of not getting sick.

The number one rule is to not touch your eyes, mouth or the inside of your nose. But this is a very hard thing to achieve. People who wear contact lenses might have a particular problem when it comes to this.

A more realistic option is to make sure your hands are clean if you do touch your eyes, mouth or nose. Wash your hands well with soap and water, and frequently apply a hand sanitizer gel containing at least 60 per cent alcohol. The latter kills bacteria and is effective against some viruses.

It’s a good idea to wipe down as many surfaces as you can with the gel or antibacterial wipes too, such as the remote control, tray table, video monitor screen and other surfaces known to have high levels of bacteria.

Try not to touch places that are accessible to a lot of people, like the top edges of aisle seats, door handles, or bathroom mechanisms. If you do, use copious amounts of gel.
Remember to wash your hands before a meal and as soon as you can after your flight.

As for face masks, these can be very helpful by preventing the spread of bacteria and viruses if you are sick, but less helpful if someone else's microscopic germs are already careering through the air towards you.

Meanwhile, a moisturising nasal spray will help combat that low humidity by helping the Mucociliary Clearance System do its work.