Driver's-Side Skin Cancer: Why UVA Through Car Windows Hits Your Left Arm
Your commute is sun exposure you've never accounted for — and the data shows it shows up on your left side.
Car side windows block only about 71% of UVA on average, compared with about 96% for windshields, and US skin cancers are more common on the left — the driver's window-exposed side.
Skin-cancer specialists note that the left-sided skew of US facial and arm cancers is consistent with chronic UVA exposure through side windows, and they recommend daily sunscreen plus UV-blocking window film for people who drive often.
Questions we get a lot
Do car windows block UV rays?
Partly. Windshields are laminated and block about 96% of UVA, but side windows block only about 71% on average, so significant UVA still reaches drivers. That's why US skin cancers are more common on the left, the side most exposed through the driver's window.
Should I wear sunscreen while driving?
Yes, especially on the left side and arm if you drive often. Because side windows let through a meaningful amount of UVA, dermatology guidance recommends daily sunscreen and considering UV-protective window film to reduce cumulative exposure during commutes.
r/SkincareAddiction: 'Why are the sun spots and freckles way worse on my left arm and left cheek than my right?'