Jet lag usually gets better within a couple of days, so I suspect there's another cause of your problems. Your cold and cough may be a clue to this.

It's quite common to pick up an infection after a long flight, because you're intensely exposed to all the bugs carried (and coughed out) by others on the plane as the air is recycled, and your immune system may be vulnerable because of the stress of travelling.

Even though you don't have a temperature, you may have a low-grade infection, so should see your GP to get your symptoms checked.

Symptoms of jet lag

These include daytime fatigue, problems sleeping at night, difficulty concentrating, headaches, irritability, loss of appetite and irregular bowel movements. Not only is sleep lost but it's of a different quality, with changes in the usual patterns of brainwaves throughout the night. The symptoms are usually worse after a flight going east rather than west, and the severity is directly related to the number of time zones that you cross.

The condition is a result of the mismatch between your internal body clock, which is running on the time frame of the place you left, and all the signals and cues telling you the time in your new environment.

Jet lag resolves swiftly with help

These symptoms usually resolve fairly swiftly, as the body clock resets itself within a few days, and there are some things you can do to aid recovery.

Helping your body adjust quickly to the new time

• Adopt local hours for sleep, wake and socialising as swiftly as possible - even if this means dragging yourself out of bed when you feel least like getting up
• Get as much exposure to natural daylight as possible
• Take meals at appropriate times
• Go outside for at least half an hour of brisk exercise every morning
• Some people use 'jet lag pills' containing compounds such as melatonin, which has the opposite effect to bright light and should be used at night to help the body to sleep (though it hasn't yet been approved for this use in the UK)

Maximising good quality sleep

• If you can't sleep and don't feel tired, rest quietly in the dark when it's bedtime
• Avoid naps because these mislead the body
• Avoid sleeping pills because although they promote sleep it isn't quite like natural sleep and they don't help the body clock to adjust

This article was last medically reviewed by Dr Trisha Macnair in April 2008