Long Haul Flights – their Side Effects on The Body

  • Author: John Parker
  • Last Updated: October 23, 2022

There is little to be said on a positive note about traveling on long haul flights. Perhaps with the exception of the excitement of a vacation to come, if that is why you are flying.

What are the side effects of long haul flights? Sitting still for many hours on end in a generally uncomfortable seat, surrounded by strangers and breathing in their germs is hardly the recipe for a healthy time. Added to that are the other side effects of long haul flights – pressurization, dehydration, tiredness and jet lag – which are all part of the fun!

Swollen legs/feet and DVT

What are the side effects of long haul flights

One of the biggest potential risks to your health on a long haul flight is the effects of sitting for so many hours in a cramped seat with your feet below your body.  That is unless you are lucky enough to fly in business or first class of course.

Sitting like that can mean the blood flow in your legs and feet can become restricted. This can then lead to swelling in the feet and legs.

In certain cases there is also a risk of DVT (deep vein thrombosis) which can have very serious consequences. People more at risk of this are those who have recently undergone surgery, those with obesity, diabetes, pregnancy, or some other serious medical conditions. If you have any of these then you might be advised to speak to your doctor.

But there are ways you can minimize the risks. Moving around, doing exercises and raising your feet for example. See my articles on compression socks and inflatable footrests.

Jet Lag

One of the most common effects of long haul travel is jet lag. This happens when you travel east to west, for example LA to Australia, or west to east, for example, New York to Rome, across many different time zones.

If you travel north to south or vice versa, for example from New York to South America or London to South Africa, then you stay roughly in the same time zone so there are no jet lag effects. The flight can still be tiring of course but that isn’t jet lag.

The most common symptom of jet lag is the inability to sleep at the correct time in the new time zone since your body clock is out of sync with your surroundings.

There are ways to combat, or at least minimize, these effects.

Read my jet lag articles –

How to prevent jet lag – my top tips that actually work

How long does jet lag last from the USA to UK

How to get over jet lag when you get home.


What are the side effects of long haul flights

The air in the passenger cabin of an aircraft flying at altitude is actually very dry. Unless you on one of the latest types of aircraft, which have climate control systems that include controlling the humidity level, then you are likely to feel dehydrated after a while.

This can make you feel tired and fatigued.

In order to prevent it drink plenty of water on the plane and avoid drinking too much, or any, alcohol, tea and coffee.

You might also consider taking some eye drops/eye spray on board with you. Your eyes may also become tired and dry so you can use this to help.

Make sure it is in a container that is no bigger than 3.4 ounces/100ml. If it is it will be confiscated at airport security. Alternatively, buy one after you go through security if there is a suitable outlet in the departure lounge.

Airplane cabin pressure affects on the body

Pressurization can cause a number of problems, in some cases. These include:


An aircraft’s cabin maintains a pressure that is equivalent to between 6,000 and 8,000 feet normally. At this “altitude” the amount of oxygen is less than at sea level.

Spending many hours at this altitude can lead to a condition known as hypoxia, meaning a lower level of oxygen in the blood. This can give you feelings of fatigue, dizziness and perhaps headaches.

Most people are not affected by this though.

Ear and tooth problems

Firstly, the change in pressure can cause ear problems including temporary partial deafness and pain. It is possible to cure these by making your ears pop. One way is to chew or suck a candy/sweet. Sometimes airlines always gave out these before take-off and landing some years ago. Another is to hold your nose, close your mouth and blow gently.

Secondly, and more rarely, is pressure-induced toothache. This can happen when a tiny amount of air is trapped below a filling. As the pressure in the cabin decreases when climbing, the air pocket in the tooth can expand. This is what can cause pain.

In 40+ years of flying, I have rarely had ear problems and never had tooth problems, and I have plenty of fillings.


This may be more of a problem for your neighbors than you, although they could be a problem for you in turn. Again, due to the decrease in air pressure as you climb, any air in your intestines is likely to expand, with obvious consequences.

There is little you can do to prevent it and the only thing you can do to alleviate it is to let it out, in the toilet, if possible. Holding it in can be uncomfortable and not particularly good for you.

I have sat next to a few champions in my time I can tell you.

Catching other passengers’ germs

What are the side effects of long haul flights

This is probably the most common of the side effects of long haul flights (and not so long).

In an aircraft holding anything from 100 to 900 passengers (yes, up to 900 in an Airbus A380 incredibly), it is inevitable that a number of them will have a cold or some other common ailment that is at the infectious stage.

Those infectious people will be sneezing, coughing and spreading their germs around the aircraft, perhaps sitting near you, walking past you in the aisle, using the toilet etc and there is a good chance that you will also become infected.

Although modern aircraft are fitted with HEPA (high-efficiency particulate air) filters I am not sure they do much to stop the spread of cold and flu germs.

Having lived in a popular vacation destination for a number of years I have seen firsthand that many people come down with a cold 2-3 days after they arrive here, having spent 4-5 hours on a flight. I would say aircraft are almost as unhealthy an environment as a doctor’s waiting room in winter.

All you can do to try and protect yourself is to ensure you wash your hands or use anti-bacterial wipes regularly. Try not to touch your mouth etc which can help bacteria and viruses spread.

Further reading from the scientific community

Frequency and prevention of symptomless deep-vein thrombosis in longhaul flights: a randomized trial

Perceived fatigue for short-and longhaul flights: a survey of 739 airline pilots

You may also find these articles useful: –

10 long haul flight tips and tricks to make it bearable

How to sleep on a plane in economy class