Altitude sickness, also called "acute mountain sickness" (AMS), is not well understood and stems from the affects of high altitude on the human body. You may have traveled to Tibet for years without incident, and then will suddenly be afflicted in severe form. In most cases, altitude problems will be limited to the first few days and then pass, apart from a persistent shortness of breath. However, in some case, it can be quite severe and even lead to death, so that you are advised to take symptoms very seriously.
Your susceptibility to AMS is not determined by physical condition. It takes time to acclimatize to the high altitude, and people who are used to walking and hiking at high altitudes can still be affected by AMS. It generally takes 1-3 days for your body to change breathing patterns and heart rate in response to the new altitude. Even after your body has initially adjusted, you may still get AMS if you continue to go higher. The best way to prevent AMS is to ascend slowly, with ample time for your body to adjust. When traveling in high altitudes, it's important to retreat to a lower height for sleeping. Travelers should avoid smoking, alcohol, and sedatives. The high altitudes cause the air to be dry and cold, so you should make sure you're well hydrated, even if it doesn't seem that you've lost a lot of water.
More noticeable in the evening, many travelers report mild symptoms such as headache, dizziness, nausea, lethargy, loss of appetite, irritability, breathlessness, and difficulty sleeping until they adjust to the atmosphere. Due to accumulation of fluid in the lungs and brain, serious symptoms may present such as breathlessness at rest, severe headache, cough, lack of coordination, fatigue, confusion, irrational behavior, vomiting, hallucinations, impaired memory, and loss of consciousness. Unfortunately, there is still much of AMS that is not understood, so travelers may develop serious problems without experiencing mild symptoms beforehand.
The best way to treat AMS is to return to a lower altitude, and in especially severe circumstances, they may need to leave Tibet. Descent should be made as quickly as possible, and the person afflicted should be accompanied by at least one other person.
Acetazolamide (Diamox) and dexamethasone are medications that are commonly prescribed, but they should be taken with care because they have masked warning signs that a retreat to a lower altitude is needed.
Herbal medications that can relieve symptoms of AMS are sometimes sold in hotels. In Tibetan, this herb is called solomano and it is known as hongjingtian in Chinese.
David Germano, Elizabeth Tseng