Acute altitude sickness occurs when an individual who is accustomed to a low altitude rapidly climbs to high altitude (above 8 000 feet).

Clinical features of mild altitude sickness include:

• Headache
• Loss of appetite
• Nausea
• Tiredness
• Dizziness
• Sleeping problems
• Swelling of arms and legs
• Breathing problems
• Palpitations

Severe altitude sickness can be fatal. 

The treatment of acute altitude sickness ranges from rest and pain relief to oxygen therapy and descent.

• Climbers to a high altitude must allow time to acclimatise.  Above 8 000 feet, no more than 1 000 feet should be climbed per 24 hour period
• Keep warm
• Keep well hydrated.  Avoid alcohol, which leads to dehydration
• Have a diet rich in carbohydrates
• Ensure only modest exercise on acclimatising days

There are medications which can help prevent altitude sickness, but are no substitute for a slow ascent.  They are used where a slow ascent is not possible e.g. when flying in to a high altitude airport.

• If a climber develops symptoms of mild altitude sickness then he/she should rest for 24 hours at that altitude 
• If a climber has more severe symptoms he/she must seek immediate medical attention and descend to the last altitude at which he/she felt well