The human body struggles at high altitudes in the Alps due to lower oxygen levels. Altitude sickness can occur above 8,000 feet and becomes more likely above 12,500 feet as the air pressure and oxygen levels drop significantly. Symptoms may include headaches, fatigue, dizziness, shortness of breath, insomnia, nausea and vomiting which are caused by the body's inability to properly absorb oxygen at high elevations.