Why Altitude Dries Out Your Skin Faster Than You'd Expect
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Why Altitude Dries Out Your Skin Faster Than You'd Expect
Most people plan for altitude by packing sunscreen and drinking more water, and stop there. That covers sunburn and altitude sickness. It doesn't cover what altitude actually does to skin, which happens faster and more aggressively than most people expect, through a mechanism that has nothing to do with heat.
The Real Mechanism: Transepidermal Water Loss
Skin loses water constantly through a process called transepidermal water loss, or TEWL — water evaporating straight through the skin barrier into the surrounding air. How fast that happens depends on the humidity gradient between your skin and the air around it: the drier the air, the faster water gets pulled out. High elevation air is typically far drier than air at sea level, and some sources tracking this at altitude have measured TEWL increasing by as much as 25% within hours of arrival. That's not a slow seasonal shift. It's a same-day change, and it happens whether or not you're sweating, whether or not you feel hot, and whether or not the temperature feels comfortable.
UV Exposure Compounds the Problem
Altitude doesn't just dry skin out — it damages the barrier that's supposed to hold moisture in, in the first place. UV radiation increases by roughly 10 to 12% for every 1,000 meters of elevation gain, according to World Health Organization figures, because there's less atmosphere above you to filter it. On top of that baseline increase, mountain terrain is full of reflective surfaces — snow, light-colored rock, water — that bounce additional UV back at skin that's already taking a heavier direct dose than it would at sea level. The result is a skin barrier getting hit by more radiation while simultaneously losing water faster than normal, which is a genuinely worse combination than either factor on its own.
Why This Sneaks Up on People
The reason altitude dehydration catches people off guard is that it doesn't feel the way dehydration usually feels. Higher elevations tend to run cooler, so the discomfort cues people normally rely on — feeling hot, sweating heavily — often aren't there, even while the actual water loss from skin is happening faster than on a hot, humid day at sea level. Wind, which is more common and more constant at elevation, adds another layer on top of the dry air itself, since moving air pulls moisture away from skin faster than still air does. By the time skin actually feels tight, cracked, or irritated, the barrier's usually already been losing the fight for a while.
What Actually Helps
Drinking more water is still the right instinct, but it's addressing the wrong side of the equation on its own — internal hydration doesn't fully offset water evaporating straight through the skin's surface. What matters more directly is protecting the barrier itself so it's not leaking moisture as fast in the first place. This is where glycerin matters more at altitude than it does most other places: cold process soap keeps its natural glycerin instead of having it stripped out for separate sale, and glycerin is a humectant, meaning it actively helps skin hold onto water instead of just not stripping what's already there. Combined with real sun protection, since the two problems are happening at once, not in sequence.
The Bars for Elevation
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The Short Version
Altitude dries out skin faster than most people expect because it's attacking on two fronts at once — pulling moisture out through the skin barrier via transepidermal water loss, while simultaneously hitting that same barrier with meaningfully more UV radiation than sea level. It doesn't feel like dehydration the way heat does, which is exactly why it catches people off guard. Drink the water, but don't stop there — the skin barrier itself needs help holding onto what it's got.
