Safety & Advisories

Altitude Sickness Explained: AMS vs HACE vs HAPE, and the Rules That Prevent Them (2026)

Altitude sickness is not one illness but three — AMS, HACE and HAPE. Here is how to tell them apart, the symptoms that signal an emergency, and the…

By Dawa Sherpa · Aug 29, 2026

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The single most important thing to understand before any high trek in Nepal is that "altitude sickness" is not one illness — it is three, and two of them can kill you within hours. Most trekkers only ever meet the mild one. But knowing how to tell acute…

Travel Himalaya Nepal · News

What altitude actually does to you

At Everest Base Camp (5,364 m) the air holds roughly half the oxygen it does at sea level. Nothing changes in the oxygen itself — the air is thinner, so each breath delivers less. Your body responds by breathing faster and making more red blood cells, a…

Travel Himalaya Nepal · News

AMS: the common one

Acute mountain sickness is the mild, common form — and the warning shot. It usually begins 6 to 12 hours after arriving at a new altitude and feels, honestly, like a hangover: a headache, plus some combination of nausea or loss of appetite, fatigue, dizziness…

Travel Himalaya Nepal · News

HACE: when it reaches the brain

High-altitude cerebral edema is AMS that has progressed to swelling of the brain. The symptom that separates it from an ordinary bad headache is unmistakable once you know it: ataxia — loss of coordination. A trekker with HACE cannot walk a straight…

Travel Himalaya Nepal · News

HAPE: when it reaches the lungs

High-altitude pulmonary edema is fluid collecting in the lungs, and it is the leading cause of altitude death. It can strike without any AMS beforehand. The signs: breathlessness that is out of proportion — gasping at rest, not just on the climb — a dry cough…

Travel Himalaya Nepal · News

The four golden rules that prevent all three

The Wilderness Medical Society's 2024 guidelines come down to four things any trekker can follow: 1. Ascend slowly. Above 3,000 m, do not increase your sleeping altitude by more than about 500 m per night, and take an extra rest day for every 1,000 m gained…

Travel Himalaya Nepal · News

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