Are you fit to fly?

Thousands of us will be catching a plane over the next few weeks for a summer escape and the last thing we need is to get ill before we even arrive.

The health problems of sitting immobile for hours in a pressurised container at 37,000ft are significant. Most air travellers are aware of the risks of deep-vein thrombosis - potentially fatal blood clots are thought to account for 2,000 deaths a year in Britain - but medical evidence now shows there are many other health hazards, ranging from the irritating to the potentially fatal.

Fortunately a few simple measures mean it's possible to prevent most of these. Here's how.

BLOOD CLOTS

The problem.

Sitting still for hours leads to "pooling" of blood in the legs, which can form clots. In most people, these are reabsorbed into the bloodstream. However, for some - such as the over-forties, cancer victims, patients who have recently had major surgery and women who are pregnant, taking the Pill or on hormone replacement therapy - the clots can find their way to the lungs. Flight-related DVTs are thought by some to be linked with cramped seating.

The solution.

If you fall into an at-risk group, seek medical advice before travelling. Otherwise, try simple in-flight exercises - such as moving your legs and feet for at least five minutes in every hour - to stop clots forming, or take frequent walks down the gangway. Wearing compression stockings designed for air travel and loose and comfortable clothing may also help. Don't cross your legs and, providing you don't suffer from bleeding disorders or gastric ulcers, take an aspirin to thin the blood.

DEHYDRATION

The problem.

The relative humidity in aircraft cabins is low, usually less than 20 per cent, which can cause discomfort in the eyes, mouth and nose. It's vital that you have a good fluid intake to reduce this dryness.

The solution.

Drink plenty before and during the flight. Stick to water or fruit juice because alcohol contributes to dehydration and fizzy drinks pump your stomach full of gases, which expand as the aircraft climbs. Use a saline spray to moisturise the nasal passages and wear spectacles rather than contact lenses.

EAR PAIN

The problem. The reduced cabin pressure means air inside the body expands. During take-off, air escapes from the middle ear and sinuses, usually without causing problems. But during the descent, the air must be allowed to flow back into the middle ear and sinuses to equalise pressure differences - which can be painful.

The solution. Ear pain can usually be cleared by swallowing, chewing or yawning. If this doesn't work, pinch your nose, close your mouth and blow. For babies, a dummy may help by stimulating swallowing.

JET LAG

The problem:

The body's internal clock becomes disrupted when you fly across multiple time zones, so when you should be sleeping you're wide awake. The result can be indigestion, general malaise, insomnia and reduced physical and mental performance.

The solution:

Make sure you're well rested before departure and take plenty of short naps during the flight. If it's a long-haul flight, try to get the same amount of sleep as you would have at home.

INFECTIONS

The problem:

In most planes, cabin air quality is high - with a level of ventilation greater than most buildings. Although up to 50 per cent of air is recirculated, it is passed through filters that trap bugs, fungi and viruses. However, there have been cases of passengers contracting TB and flu from other infected travellers.

The solution:

If you have been diagnosed with an infectious disease, you should not travel by air. Passengers placed next to someone with obvious symptoms of a contagious disease can ask to be moved.