Can mountains make you sick?

If you eat one, yes. But seriously, people can get sick when they go to high points, such as mountaintops. This is called altitude sickness. Most people are OK up to about 8,000 feet (2,438 meters). Above that, some people might get a headache, or feel dizzy, tired, short of breath, and sick to their stomach. Why? There's less oxygen at such heights, though you can still breathe. If you get altitude sickness and your body doesn't adjust, there's only one cure: Go back down to a lower altitude.