Altitude sickness, sometimes called mountain sickness, causes discomfort when someone rises too high too soon. It can affect people like mountain climbers and skiers visiting areas such as the Alps. Sometimes symptoms can occur after flying direct to higher ground rather than staggering the journey.
No mountain in the UK is high enough to cause altitude sickness, but precautions are advised when travelling to places more than 2,500m above sea level.
Symptoms of altitude sickness
Symptoms of altitude sickness are due to reduced oxygen at height and range from a mild headache, nausea, exhaustion and feeling dizzy - known as acute mountain sickness (AMS) - to a life-threatening build-up of fluid in the lungs and/or brain.
In cases of severe altitude sickness additional symptoms may include a bubbling noise from the chest, being out of breath, coughing up pink sputum, problems walking, clumsiness, confusion or loss of consciousness. This is a medical emergency.
One serious form of altitude sickness is high altitude pulmonary oedema (HAPE). Fluid builds up in the lungs affecting breathing. HAPE often comes on quickly. If left untreated, it can progress to respiratory collapse and there's a risk of death.
Another severe form of altitude sickness is high altitude cerebral oedema (HACE). In this condition, fluid builds up in the brain. The brain swells affecting the person's mental state. This can be life-threatening unless prompt action is taken.
In case of altitude sickness
If mild altitude sickness symptoms are experienced, the person should not go any higher for at least 24-48 hours until symptoms ease. If symptoms don't improve, descending around 500m may be advised.
Anyone with symptoms of severe altitude sickness, such as HAPE or HACE, should descend immediately and seek urgent medical help.
Precautions to take to help prevent altitude sickness include planning trips carefully to allow the body to adapt to progressively higher locations before moving further upwards. This is known as acclimatisation. People should ascend gradually - no more than 300m (1000 feet) per day. Professional climbers sometimes carry the drug acetazolamide, which helps to reduce the risk of AMS in some people.
Keeping hydrated and avoiding alcohol at heights are also recommended.