Short answer: Yes — you can get meaningful sun damage through a closed car window, just usually not a classic red sunburn. Automotive glass blocks nearly all UVB (the burning wavelength), but side windows let a lot of UVA through. A 2016 JAMA Ophthalmology study of 29 vehicles found windshields blocked about 96% of UVA on average, while side windows blocked only about 71% — with some as low as 44%. UVA is the wavelength most associated with photoaging and skin cancer, so a long drive with your arm by the glass is real exposure. The simplest fix is a long-sleeve UPF-rated shirt, because unlike sunscreen it does not wear off at hour three.
Why doesn't glass stop UV the way people assume?
Not all automotive glass is the same, and that's the whole story.
- Windshields are laminated glass — two sheets of glass bonded to a plastic (PVB) interlayer. That interlayer absorbs UVA very effectively, which is why windshield numbers come in around 96%.
- Side and rear windows are usually tempered glass — a single heat-treated sheet with no interlayer. Tempered glass absorbs UVB well but is much leakier on UVA. Panoramic roofs and sunroofs vary widely depending on the coating.
Because UVB is what causes the immediate red burn, most people conclude nothing is getting through. UVA doesn't announce itself the same way. It penetrates deeper into the dermis, drives collagen breakdown and pigmentation, and accumulates quietly over years of commuting.
| Glass type | Where it is | UVA protection |
|---|---|---|
| Laminated | Windshield (and increasingly front side windows on newer cars) | High — roughly 96% average |
| Tempered | Most side and rear windows | Variable — roughly 44–96%, ~71% average |
| Glass roof / sunroof | Overhead | Depends entirely on the coating; check your manual |
What is "driver's arm" — and is it actually a thing?
It's the informal name for the asymmetric sun damage that shows up on the left arm and left cheek of drivers in right-hand-traffic countries like the U.S. And the epidemiology backs it up: a large analysis published in the Journal of the American Academy of Dermatology reviewing tens of thousands of U.S. skin cancer cases found a left-side skew — roughly 52% of arm cases and 51% of facial cases on the left. In left-hand-traffic countries, the pattern reverses to the right side. That directional flip is the strongest clue that driving exposure is a genuine contributor rather than a statistical fluke.
You don't need to be a long-haul trucker for this to matter. A 45-minute commute each way, five days a week, is roughly 400 hours a year with one arm parked next to leaky glass.
Does window tint solve it?
Partly, and with caveats. Most quality aftermarket films — including clear ceramic films with no visible darkening — block 99% of UV. That's a legitimate upgrade. But three things limit it:
- Legality. Visible light transmission limits vary by state, and dark front-window tint is restricted or illegal in many of them. Clear UV film is usually the compliant option.
- Cost and permanence. It's a per-vehicle fix. Rental cars, work trucks, and a friend's truck on a fishing trip are all unprotected again.
- Open windows. Tint does nothing with the window down, which is exactly how a lot of people drive in summer.
Clothing travels with you. That's the practical argument for solving this at the sleeve rather than at the glass.
What should you wear on a long drive?
Think of it as the same problem as a day on the water: sustained, low-intensity UVA on a fixed patch of skin, in a warm environment where you don't want to overheat.
- Long sleeves with a real UPF rating. UPF 50+ means less than 1/50th of UV reaches the skin, and unlike sunscreen it doesn't need reapplying. Sleeve length is the part people get wrong, so check it before you buy: our Men's Lightweight Sun-Protective Shirt is a genuine long sleeve in a tightly-woven nylon-stretch weave, which is what puts physical coverage over the forearm resting on the door.
- Light colors for a hot cabin, but don't over-index on it. Color affects heat more than it affects UV in a properly rated fabric — the UPF rating is what's doing the protective work.
- A quick-dry weave for the seat-back sweat problem. Long drives in August mean a wet back at the rest stop. The long-sleeve Men's Adventure Tech Shirt uses a polyester-rich quick-dry weave that moves moisture instead of holding it, which matters when you get out of the car and walk straight into somewhere. If you want the same treatment for the torso without the sleeves, the Pro-Performance Quick-Dry Shirt is the short-sleeve version — just understand you are back to sunscreen on the forearms.
- Sunscreen on what's left. Left hand, left side of the neck and face, and the back of the hand on the wheel. Fabric handles the arm; SPF 30+ handles the gaps.
- Sunglasses that state UV400. The same 2016 research was motivated by cataract risk, not just skin.
How do you know a shirt's UPF claim is real?
A few honest markers, since this category has a lot of vague marketing in it:
- UPF is a rated standard (ASTM D6603 / AATCC 183 in the U.S.), unlike "sun-protective" as a loose adjective. Look for a number, not a vibe.
- Tighter weave and higher fabric density generally mean better UV blocking. Hold it up to a light — if you can see through it easily, UV is getting through too.
- Synthetics like polyester block UV inherently better than untreated cotton, which is part of why an ordinary white cotton tee only lands around UPF 5–7 when it's dry, and worse when it's wet.
- Coverage beats rating. A UPF 30 long sleeve protects more total skin than a UPF 50 short sleeve.
Apply those four checks to whatever you already own before buying anything — a long-sleeve shirt you like is worth more than a rated one that stays in the closet. If you do need a sleeve for the drive, our breathable summer hiking and sun-protection range covers the tight-weave lightweight options, and the wider Shirts & Tops collection has the long-sleeve field and work shirts if you want coverage with a more everyday look.
Frequently asked questions
Can you get a sunburn through a car window?
A true red burn is unlikely, because automotive glass blocks nearly all UVB — the wavelength responsible for burning. But UVA passes through side windows in significant amounts, and UVA causes photoaging, pigmentation, and contributes to skin cancer risk. So the damage is real even when the burn isn't.
Which side of the car gets the most sun damage in the U.S.?
The left — driver's side. Skin cancer case data shows a left-side skew on the arms and face for U.S. drivers, and the pattern reverses in countries that drive on the left.
Is a UPF shirt hotter than a short-sleeve tee in the car?
Usually not, if the fabric is designed for it. A lightweight, breathable UPF shirt shades the skin and lets sweat evaporate, which is why long sleeves are standard on the water and in the desert. A heavy cotton long sleeve, on the other hand, absolutely will be hotter.
Do I still need sunscreen if I'm wearing a UPF 50 shirt?
Yes, on anything the shirt doesn't cover — hands, neck, face, and ears. The shirt handles the arms and torso permanently; sunscreen covers the rest and needs reapplying every two hours.
Does UPF wash out over time?
Ratings on tightly-woven synthetic fabrics hold up well through normal washing. Wash cold, skip fabric softener and bleach, and avoid high-heat drying — those are what degrade the fibers and the fit.