Dehydration is another problem. Some Mt. Everest climbers get frost bite because they take off their mask. Extreme cold can cause hypothermia, which slows the heart and can lead to death. You can get frostbite like Seaborn Beck Weathers did. They drink liters of water before climbing.
High altitudes can affect the brain, creating confusion, bad judgement, and other problems.
So be prepared if you go climbing at high altitudes. I felt sick, and had a migraine-type headache. I was sweaty and felt pretty awful. The expedition leader realized that Willis was suffering from altitude sickness, and unrolled a long nylon tube from a bag. Willis climbed inside, and the tube inflated with a foot pump.