Altitude sickness — sometimes called mountain sickness — affects mountain climbers, hikers and other people at high altitudes. Mild cases of altitude sickness might involve a headache and a feeling of extreme exhaustion.
Serious cases can involve a life-threatening build-up of fluid in the lungs (called high altitude pulmonary edema (HAPE)) or the brain (called high altitude cerebral edema (HACE)). HAPE can make breathing very difficult. If untreated, HAPE can lead to respiratory failure and even death. Similarly, HACE can lead to swelling in the brain, coma and ultimately death.
As elevation increases, the amount of oxygen in the air decreases. If you climb or hike a tall mountain, your body has to adjust to the fact that there's less oxygen in the air. Altitude sickness usually occurs at elevations above 8,000 feet.
Altitude sickness can be triggered by ascending too rapidly. It can also happen if you overexert yourself during the first 24 hours at a higher altitude. Extremely cold weather and not drinking enough water might also result in altitude sickness.
If you're heading toward a high-altitude area, you should be aware of the signs and symptoms of altitude sickness. These can include exhaustion, headache, nausea, dizziness, shortness of breath, lack of appetite and trouble sleeping.
HAPE and HACE have more severe symptoms. These can include trouble breathing, coughing, fever and lack of coordination. If any of these symptoms occur, it's important to get to a lower elevation as soon as possible and seek professional medical treatment.
With cases of mild altitude sickness, you should stop any further ascent until your symptoms improve. Get to a lower elevation, drink plenty of water and get some rest. Use over-the-counter pain relievers for headache. Keep an eye on your symptoms and, if they don't improve, seek medical help as soon as possible.