At high altitudes, you may develop symptoms of acute mountain sickness (AMS) . Just about everyone who ascends to around 4000m or more experiences mild symptoms, but serious cases are rare. The simple cure - descent - almost always brings immediate recovery.

 

AMS is caused by the fact that at high elevations there is not only less oxygen, but also lower atmospheric pressure. This can have all sorts of weird effects on the body: it can cause the brain to swell and the lungs to fill with fluid, and even bring on uncontrollable farting. The syndrome varies from one person to the next, but symptoms include breathlessness, headaches and dizziness, nausea, difficulty sleeping and appetite loss. More extreme cases may involve disorientation and loss of balance, and the coughing up of pink frothy phlegm.

AMS strikes without regard for fitness - in fact, young people seem to be more susceptible, possibly because they're more reluctant to admit they feel sick and they dart about more energetically. Most people are capable of acclimatizing to very high altitudes but the process takes time and must be done in stages. The golden rule is not to go too high, too fast; or if you do, spend the night at a lower height ("Climb High, Sleep Low"). Above 3000m, you should not ascend more than 500m per day; take mandatory acclimatization days at 3500m and 4000m - more if you feel unwell - and try to spend these days day-hiking higher.

The general symptoms of AMS can be treated with the drug acetazolamide (Diamox) but this is not advised as it will block the early signs of severe AMS, which can be fatal. It is better to stay put for a day or two, eat a high carbohydrate diet, drink plenty of water (three litres a day is recommended), take paracetamol or aspirin for the headaches, and descend if the AMS persists or worsens. If you fly direct to a high-altitude destination such as Leh, be especially careful to acclimatize (plan for three days of initial rest); you'll certainly want to avoid doing anything strenuous at first.

Other precautions to take at high altitudes include avoiding alcohol and sleeping pills, drinking more liquid, and protecting your skin against UV solar glare