It is even more important to protect yourself from the sun at high altitude, where you run even more of a risk of burning than at sea level. Ultraviolet rays are more powerful at altitude. So, you need to wear a protective sunscreen, even on overcast days as ultraviolet rays still penetrate the cloud cover.
What protection factor you will need is something that you have to judge. Bear in mind that the sun is much stronger at glacier altitude (around 3000m) than low valley slopes (maybe as low as 600m), and that the sun gets gradually stronger from Christmas onward.
Because of the intensity of the sun at altitude - the glare is especially intense when reflected by the snow - good eye protection is also essential. Snow blindness is particularly dangerous and painful - sufferers run the risk of permanent eye damage depending on how extreme it is. Even in less severe cases, though, the sufferer will not be able to see properly for a number of extremely painful days before sight returns.
Always wear good-quality sunglasses or goggles to avoid damaging your eyes. The lenses should not only cut the glare but filter the strong UV rays as well. Most good skiing and snowboarding retailers stock a wide range of sunglasses and goggles.
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