Sun protection · 16/06/2026
Why skin can sun-damage on a day that never saw direct sunlight
UVA rays, responsible for a large share of cumulative photoaging, pass through cloud cover and standard window glass largely unimpeded — meaning the "no sun today" assumption that justifies skipping SPF is wrong more often than people think.
Why cloud cover blocks far less UV than it feels like it should
Clouds primarily scatter visible light, which is why an overcast day feels dimmer — but UVA radiation, the wavelength most responsible for long-term cumulative photoaging (as opposed to UVB, more associated with sunburn), passes through cloud cover with relatively little attenuation. A cloudy day can still deliver a meaningful UVA dose even though it doesn't feel "sunny" in the way that triggers the instinct to apply sunscreen.
Why being indoors near a window doesn't fully solve the problem either
Standard window glass blocks most UVB but allows a significant proportion of UVA through largely unimpeded — meaning a desk near a window, a long car commute, or simply a bright indoor room with natural light can deliver cumulative UVA exposure across a full year that adds up meaningfully, despite never involving direct outdoor "sun time" in the way most people picture sun exposure.
Making SPF a true daily habit independent of weather or location assumptions
Apply sunscreen every morning regardless of forecast, season or whether the day's plans are entirely indoors — treat it as a non-negotiable daily habit rather than a conditional response to visibly sunny weather. This year-round consistency, rather than selective sunny-day-only application, is what actually prevents the cumulative photoaging that UVA exposure causes over months and years.
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