Reactions to acute exposure to high altitude and the process of acclimatization has been of scientific interest since many years. High altitude illnesses are specified by three different entities: acute mountain sickness (AMS), high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE). Prevalence of AMS is known to be between 10 to 20% for altitudes between 4000 and 5000m, increasing significantly in higher altitude. The prevalence depends on the ascent rate, individual susceptibility and physical exhaustion.