What is an altitude sickness?

Altitude sickness occurs when you cannot get enough oxygen from the air at high altitudes. This causes symptoms such as headache and not feeling like eating. It happens most often when people who are not used to high altitudes go quickly from lower altitudes to 8000 ft (2438 m) or higher. For example, you may get a headache when you drive over a high mountain pass, hike to a high altitude, or arrive at a mountain resorts.