Altitude illness is common among unacclimatised individuals travelling to altitudes over 2500 m. With increasing numbers of tourists travelling to high altitude environments globally, many are being exposed to potentially significant risks. There are tour operators in Australia that offer treks to Nepal, South America and Mt Kilimanjaro, where hiking to extreme altitudes (defined as >5500 m) can be achieved without any technical climbing experience, making these expeditions readily available to the general population. In addition, some international ski resorts expose travellers to altitudes of almost 4000 m (e.g. Breckenridge, Zermatt, Chamonix, Aspen Snowmass), which can be underestimated.