Altitude sickness is the result of travel from a lower elevation to a higher elevation. It affects about 20 percent of people below the altitude of 18,000 feet (5,500 meters) and about 50 percent of people above the altitude of 18,000 feet. Altitude sickness can be divided into three different types of illness, the most common and least dangerous of which is acute mountain sickness. The other two, high-altitude pulmonary edema and high-altitude cerebral edema, are more serious conditions. Most cases of acute mountain sickness go away on their own after a few days' adjustment to a new elevation. The symptoms of acute mountain sickness include headaches, dizziness, shortness of breath, stomachaches, fatigue and difficulty sleeping.
To prevent or reduce altitude sickness, you need to be fully hydrated. In addition, you should limit your intake of caffeine and alcohol -- at least until you adjust to the new altitude. While there are some medications and herbal supplements you can buy over the counter to alleviate altitude sickness, some people prefer vitamins. Both vitamin C and vitamin E are said to help with altitude sickness, as are other antioxidants. Antioxidants like beta carotene, selenium and zinc help because they reduce the free radicals suspected to exacerbate altitude sickness. Antioxidants can help you breathe more easily. While studies haven't proven that vitamins and antioxidants definitely help with altitude sickness, they seem to point in that direction. Extra vitamins are probably a good addition to any traveler's irregular diet, anyway. The recommended dosage of vitamin C is 2,000 to 3,000 milligrams per day while the dosage of vitamin E is 400 international units (iu) a day.
To further ease your altitude sickness, you should ascend to high altitudes gradually, adding no more than 1,000 feet (300 meters) to your sleeping elevation each day. If your symptoms don't pass after a few days, you may need to descend and seek medical attention.