Travelers who will be visiting mountain areas should be prepared to recognize and respond to the symptoms of altitude illness, which are caused by the lower level of oxygen available at high elevations. Common symptoms are headaches, red eyes, fatigue, and loss of appetite. Although the human body can adjust to changes in altitude, the process (called acclimatization) takes time.

Each person has their own "acclimatization line." Below it you probably won't experience altitude sickness, but going above it causes symptoms to begin. For most people, this line initially lies somewhere near 9,000 feet (2,700 meters), but it can be adjusted by following preventive techniques.

Recommendations

- Symptoms of altitude illness occur during ascent, not descent. The simplest way to avoid or reduce the symptoms of altitude illness is to ascend slowly to give your body time to become accustomed to changes in oxygen concentration.

- It is also important to increase your fluid intake to counteract symptoms of dehydration induced by dry mountain air and increased respiratory rate.

- Spending the night at or just below one's acclimatization line gives the body time to adjust. If you begin to feel symptoms of altitude illness, you are probably near your acclimatization line.

- During the first couple of days, avoid drinking alcohol or using any unnecessary medications, since their effects may be increased at high altitudes. Sleeping pills and tranquilizers in particular can cause serious problems at high altitudes because they can decrease the breathing rate. Aspirin or ibuprofen can be used for headache.

- Eat light. Chicken soup or other healthy light dishes is recommended for a fastest digestion and better acclimatization.

- Limit your activity level and remain at the same altitude for a day or two before resuming your ascent.