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Health and safety when flying


Travel-related deep vein thrombosis (DVT)

One topic that has caused considerable interest is the possible link between deep vein thrombosis (DVT) and air travel. Immobility is the most common risk, and may be associated with any form of long distance travel, whether by air, car, coach or train. Although the vast majority of passengers have nothing to fear, we have reproduced the following preliminary Department of Health (DoH) advice, pending further study, regarding this condition.

What is DVT?

DVT is a serious condition where blood clots develop in the deep veins of the legs. It must be distinguished from blood clots in superficial varicose veins in the legs, called phlebitis, which is much less serious. One in every hundred people who develops DVT, dies. The cause of death is usually a blood clot, travelling from the legs to the lungs. This is called a pulmonary embolus or PE. When PE is severe, it causes the lungs to collapse and leads to heart failure. Treatment of DVT and PE is with blood thinning drugs or anticoagulants, including Warfarin and Heparin. Aspirin in low doses also acts as a blood-thinning drug and is used to prevent clotting conditions in the arteries, for example, coronary thrombosis. Its benefit in preventing DVT is debatable. DVT combined with PE or other blood clots is often referred to as Venous thromboembolism or VTE.

Who is at risk of DVT?

Every year DVT occurs in about 1 in 2000 people in the general population, ranging from 1 in 3000 in people under the age of 40 up to 1 in 500 in those over 80.

The risk of DVT is greater in people:

  • Over 40 years of age
  • Who have had blood clots already
  • With a family history of blood clots
  • Suffering from or who have had treatment for cancer
  • With certain blood diseases
  • Being treated for heart failure and circulation problems
  • Who have had recent surgery, especially on the hips or knees
  • Who have an inherited clotting tendency

DVT is also more common in women who:

  • Are pregnant
  • Have recently had a baby
  • Are taking the contraceptive pill
  • Are on hormone replacement therapy (HRT)

These groups make up to 90-95% of those who get DVT and/or PE.

The risk of DVT from air travel

There is some evidence that long-haul flights, especially when passengers have little or no exercise, may increase the risk of developing DVT. Information on the proportion of people who develop DVT related to air travel is limited, but experts suggest this is small. Also, it is not easy to decide whether the flight itself caused the DVT/PE or whether these people were at risk for other reasons. This is because:

  • DVT and PE are relatively common conditions anyway and
  • more people than ever now travel by air every year.

While it is difficult to be certain what the exact causes of travel-related DVT are, experts agree that lack of exercise or immobility are major underlying risks. They have also identified that people at increased risk of DVT/PE in general, are those more likely to develop travel-related DVT/PE.

What are the signs of DVT?

You may get swelling, pain, tenderness and redness especially at the back of the leg below the knee. This is different from the mild ankle swelling that many people get during long haul flights and DVT usually, though not always, affects only one leg. These complaints may develop during the journey, but more commonly, hours or even days later. The pain may be made worse by bending the foot upward towards the knee. In some cases there may be no signs or symptoms of DVT at all in the legs, and problems only become obvious when a pulmonary embolus or PE develops from the clots in the legs. Fortunately PE is rare. PE can cause breathlessness, chest pain and in severe cases, collapse. Both DVT and PE, whatever the cause, are serious conditions and need urgent investigation and treatment.

How to reduce the possible risk of DVT

Before the trip, consult your doctor if you have:

  • Ever had a DVT or PE
  • A family history of clotting conditions
  • An inherited tendency to clot (thrombophilia)
  • Cancer or had treatment for cancer in the past
  • Undergone major surgery in the last three months
  • Had hip or knee replacement within the last three months
  • Ever suffered from a stroke

Some experts advise that people who have had hip or knee replacements should postpone long haul flights for three months after surgery. If you have had this kind of surgery, talk to your family doctor, travel clinic staff or a member of the surgical team.

You may need advice on in-seat exercises, especially leg exercises, to keep the circulation active and reduce the risk of developing a DVT. Some information is provided below. More information is available in literature provided by travel agents, and in the in-flight leaflets, magazines and videos now produced by many airlines.

You may also need to discuss treatment with blood-thinning drugs or the use of elastic stockings if you are in a high-risk group. While there is some evidence that elastic stockings may be useful, there is no evidence that aspirin is effective in preventing travel-related DVT or PE. Elastic stockings are widely available from pharmacies and pharmacists can provide advice on use and fitting. Because aspirin can have serious side effects like bruising, bleeding from the gut and allergies, you should consult your doctor before deciding to take this drug. People taking aspirin already should not increase the dose.

Women taking the pill or on hormone replacement therapy (HRT) should do the exercises described in this advice to help reduce the risk. They should also discuss the use of elastic stockings with their community pharmacist. Women who are pregnant, or have recently had a baby, should seek advice from the antenatal team or the health visitor.

During the trip:

  • Be comfortable in your seat
  • Bend and straighten your legs, feet and toes while seated, every half-hour or so during the flight
  • Press the balls of your feet down hard against the floor or footrest to help increase the blood flow in your legs and reduce clotting
  • Perform upper body and breathing exercises to further improve circulation
  • Take occasional short walks, when in-flight advice suggests that this is safe
  • Take advantage of refuelling stopovers, where it may be possible to get off the plane and walk about
  • Drink plenty of water
  • Be sensible about alcohol, which in excess, leads to dehydration and immobility
  • Avoid taking sleeping pills, which also cause immobility

After the trip:

For the vast majority of air passengers, there will be no problem. If, however, you do develop breathing difficulties or swollen and painful legs, especially where one is more affected than the other, see a local doctor urgently or go to the nearest Accident and Emergency Department.

What is being done?

More good research is needed to find out the real connection between DVT and air travel, what the scale of the problem is and how it can be prevented. The DoH and the Department for Transport, Local Government and the Regions (DTLR) have set up the Aviation Health Working Group to oversee this research and to provide advice to air travellers and the airline industry. The group will help to ensure that further research ties in with that being undertaken by the World Health Organisation, and is supported by the aviation industry.

Further information on travel related DVT is also available on the internet on the Department of Health's website.


In most departure lounges there are cafes and bars. Beware of drinking too much whilst you wait for your flight. Captains have the right to stop you getting on the plane if they think you're drunk. They will stamp 'Refused Boarding' on your ticket and you will probably find that other airlines will also refuse to carry you. You will not be entitled to a refund.

Be aware that it takes less alcohol to make you drunk when you're flying because of the pressurisation of the aircraft. If you overdo it, it won't just be jet lag you have to cope with at the other end.

Health advice for air travellers

The Department of Health issues a free booklet, "Health Advice for Travellers" which gives information about inoculations and other health precautions. If you have any concerns about your fitness to fly, talk to your doctor before you book your flight. (If you are pregnant, you should talk to your doctor and the airline. Most airlines will not carry you when you are more than 28 weeks into your pregnancy - the number of weeks can vary between carriers. (And remember to take account of the stage you will be at when you are due to fly home.) The Civil Aviation Authority (CAA) has a helpful page of FAQs on air travel passengers' health and safety.

Health and safety FAQ