You absolutely sunburn faster at higher altitudes due to a measurable increase in solar ultraviolet (UV) radiation exposure. UV radiation is a form of electromagnetic energy emitted by the sun, which carries enough energy to damage skin cells. This heightened risk results from physical and environmental factors unique to elevated areas. This article explains the specific mechanisms behind this phenomenon and provides strategies to protect your skin.
Why UV Exposure Increases with Elevation
The primary reason for increased UV exposure at altitude is the reduced mass of the Earth’s atmosphere above you. The atmosphere acts as a natural filter, absorbing and scattering much of the incoming solar radiation, particularly the shorter-wavelength, damaging UV-B rays. As elevation increases, there is less air overhead to perform this filtering function.
This relationship is quantifiable, with UV intensity increasing by roughly 4% to 5% for every 1,000 feet (about 300 meters) of elevation gain. The air is less dense at these heights, meaning fewer molecules are available to block the radiation before it reaches your skin. This atmospheric thinning is a constant physical reality, making sun protection necessary even on seemingly mild days.
This thinning allows a greater percentage of high-energy UV-B radiation to penetrate, which is responsible for causing sunburn. While UV-A radiation contributes to skin aging, the proportional increase of UV-B is a major factor in the accelerated rate of sunburn at altitude.
Intensifying Factors Unique to High Altitude
Beyond the primary effect of atmospheric thinning, specific environmental conditions at high altitudes dramatically amplify UV exposure. The most significant factor is the high reflectivity of snow and ice, known as the albedo effect. Fresh snow can reflect up to 80% of the UV radiation that hits its surface, effectively doubling the dose your skin receives. This reflected radiation hits the skin from below and the sides, reaching areas often shielded when the sun is directly overhead, such as the underside of the chin and nasal passages.
This increased exposure makes winter activities hazardous for unprotected skin. The effect is so pronounced that severe sunburn can occur even on an overcast day if surrounded by snow.
People often underestimate the danger because of clouds. While thick clouds reduce UV radiation, thin or scattered clouds common at high altitudes may not block a significant amount of UV. In some cases, thin cloud cover can even scatter the radiation, increasing the amount of UV reaching the ground compared to a clear sky. Relying on a cloudy day as sun protection is a dangerous misconception when at elevation.
Essential High-Altitude Sun Protection Strategies
Given the heightened risk from atmospheric thinning and environmental factors, specialized sun protection is necessary at elevation. Opt for broad-spectrum sunscreens with a Sun Protection Factor (SPF) of 30 or higher, as the intensity of UV exposure demands a robust barrier. The high-energy UV rays at altitude require a greater concentration of active ingredients to prevent skin damage.
It is necessary to reapply sunscreen frequently—at least every two hours—and more often if you are sweating or exposed to wind. The dry, windy conditions common at high altitudes can cause sunscreen to wear off more quickly than at sea level. A generous application is needed on all exposed skin, including commonly missed spots like the ears, the back of the neck, and the tops of the feet.
Physical barriers are also a non-negotiable part of high-altitude protection. Wearing a wide-brimmed hat provides consistent shade to the face and neck, mitigating the risk from direct and reflected light. Wraparound sunglasses are necessary to protect the eyes and the delicate skin around them from intense, reflected UV radiation, which can otherwise cause a painful condition known as snow blindness.