First symptoms of altitude sickness are shortness of breath, headaches and trouble falling asleep. Next will be fatigue and unusual tiredness. More moderate symptoms will be nausea, dizziness and shortness of breath without exertion.
Severe Symptoms: Severe altitude sickness can cause relentless nausea and vomiting that prevents keeping fluids down, shortness of breath even at rest, and neurological changes such as confusion, clumsiness, or difficulty walking straight—warning signs of High Altitude Cerebral Edema (HACE). In the lungs, it may progress to a cough with pink, frothy sputum and extreme breathlessness, indicating High Altitude Pulmonary Edema (HAPE).
