It's summer holiday season - and while jetting off somewhere sunny is all about fun and relaxation, planes can come with their own set of health risks.
The first to spring to mind is deep vein thrombosis (DVT), a blood clot that develops in one of your body's deep veins, usually in the leg. It can occur on dry land, but is associated with flying - mainly long-haul flights - due to sitting in one position for so long.
"The human body was designed for movement, not to stay still. Prolonged sitting - staying in one position for a long period of time - adds to the static load on our musculoskeletal system, and prevents effective circulation of blood through your body," explains Jay Brewer, professional head of Clinical Wellbeing at Nuffield Health.
But, surely this is something you only need to worry about once you reach a certain age? Actually no. Here's what you need to know if you're travelling this summer.
DVT affects younger people too:
Actually, while it is more common in older age groups (DVT affects around one in every 1,000 people, mostly over-40s), it can affect younger people, and there are some specific risk factors that may apply to younger women.
Generally, the chances of developing a blood clot on a flight are slim, so there's no need to panic. But it's worth being clued up about the warning signs, and any circumstances that may mean you need to take extra care.
Professor Mark Whiteley, renowned vascular expert and founder of The Whiteley Clinic, says: "While it's true that as you age and become less active you have a slightly higher risk of blood clots, some of the patients we see are in their 20s and 30s.
"Also, while women have an increased chance of developing blood clots due to lifestyle factors such as pregnancy, or taking birth control, research has found that men actually have a higher rate of developing DVT naturally."
The contraceptive pill or pregnancy hormones can put you at a higher risk:
Pregnancy can be associated with a higher risk, due to the weight of the baby reducing blood flow to the legs. Plus, hormones and blood composition change during pregnancy, which can influence clotting.
There are warnings that the combined contraceptive pill can increase the risk of DVT due to the levels of oestrogen in the pill and oestrogen can cause the blood to clot more easily.
However, not all birth control pills are linked with any increased risk, and certain individuals may still be more likely to develop a clot, such as people who are overweight or have a history of blood clots.
Having a condition or treatment that can cause your blood to clot more easily, such as cancer (and chemotherapy and radiotherapy), heart and lung disease or inflammatory bowel disease, should also be considered as factors in the possibility of developing DVT.
If you're concerned or unsure, speak to your GP for advice.
Symptoms to look out for:
Warning signs can include pain, swelling, tenderness, a heavy ache in the affected area and warm, red skin. Often the pain can become more severe when you bend your foot upwards towards the knee.
If you notice any possible symptoms, it's important to get it checked with a medical professional as soon as possible. If a blood clot's suspected or diagnosed, you may need anticoagulant medicine to reduce further clotting and stop any existing clots getting bigger.
The condition is highly treatable, but in more severe cases and without prompt treatment, serious complications can sometimes occur - including pulmonary embolism, where a piece of the clot breaks off and travels through your bloodstream into your lungs.
What you can do to help prevent DVT:
A number of things are recommended to decrease the likelihood of DVT while flying. Compression socks can help speed up blood flow in the veins, which can cut the risk of clots, and are an especially good idea on long-haul flights.
Try not to stay in your seat in one position for too long either - have a stretch and move your feet and legs frequently, even when you're stuck in your chair.
"I always advise people to keep as active as possible when flying, and ensure you walk up and down the cabin aisle at least once per hour," says Whiteley.
Stopping smoking and keeping generally fit and healthy helps too.