Key takeaways
- Extra spots and wrinkles on a frequent driver's window-side cheek are linked to UVA coming through the side window.
- The window gap: In a study of 29 cars, windshields blocked an average of 96% of UVA, while driver-side windows blocked 71% (range 44% to 96%).
- In one set of skin cancer records, men had a stronger tendency toward cancers on the left side, the driver's side in the U.S.
- Check first: A spot that's changing in size, shape, or color, or that itches or bleeds, needs a doctor before any cosmetic treatment.
If you drive a lot and one side of your face has more spots and wrinkles, the sunlight coming through your side window may be part of the reason. The American Academy of Dermatology notes that UVA rays, which cause wrinkles and age spots, can pass through window glass. Windshields block most UVA, but driver-side windows vary widely from car to car.
Is One Side of Your Face Really Aging Faster?
Is One Side of Your Face Really Aging Faster?
It isn't just your imagination. The AAD calls UVA the "aging rays" and says they can prematurely age your skin, causing wrinkles and age spots, and that they can pass through window glass. You don't feel a burn behind the wheel, but the skin facing the window still gets a little UVA every time you drive.
There are documented cases where this showed up on just one side. In 2012, the New England Journal of Medicine published an image case titled "unilateral dermatoheliosis," meaning sun damage that built up on one side of the face. In countries where you sit on the left, that's usually your left cheek.
Is One Side of Your Face Really Aging Faster?
When you compare sides in the mirror, look at three things together: the number of spots around your cheekbone and temple, whether lines near your eyes stay when your face is relaxed, and whether the skin feels rougher under your fingertips. If all three are more noticeable on the window side, your driving habits are worth factoring in.
How Much UVA Do Car Windows Actually Block?
How Much UVA Do Car Windows Actually Block?
There's a real gap between the windshield and the side windows. A 2016 study of 29 cars found that windshields blocked an average of 96% of UVA, while driver-side windows blocked just 71% on average. Side windows ranged from 44% to 96%, and only 4 of the 29 cars blocked more than 90%.
A 2025 study of 34 gas, hybrid, and electric vehicles found the same pattern: 99.25% for windshields versus 88.78% for driver-side windows on average. In that study, mileage, not model year, was linked to how much UVA the driver's window blocked. Both studies measured cars at U.S. dealerships, so your own car may differ.
| What was measured | 2016 study (29 cars) | 2025 study (34 cars) |
|---|---|---|
| Windshield UVA blocked | 96% on average | 99.25% on average |
| Driver-side window blocked | 71% on average (44%–96%) | 88.78% on average |
| Also noted | 4 cars blocked over 90% | Mileage mattered more than model year |
How Much UVA Do Car Windows Actually Block?
You can't tell which kind of window you have by looking at it. That's why a sunscreen habit on driving days is a more reliable fix than counting on the glass.
Which One-Sided Spots Should a Doctor See First?
Which One-Sided Spots Should a Doctor See First?
Before you think about fading spots, look for any that are changing. A 2010 review of skin cancer patients found slightly more cancers on the left side (52.6%) than the right (47.4%), and the tendency was stronger in men. These were patients referred to one academic center, so the numbers won't apply to everyone, but they're a good reason to check the more sun-exposed side carefully.
The AAD's ABCDE warning signs of melanoma are:
- Asymmetry: one half of the spot doesn't match the other half
- Border: the edge is irregular, scalloped, or poorly defined
- Color: the color varies within the spot
- Diameter: usually larger than 6 mm (about a pencil eraser), though it can be smaller
- Evolving: the spot looks different from the rest or is changing in size, shape, or color
Make an appointment if you notice a new spot, one that looks different from others, or one that's changing, itching, or bleeding. Don't have a spot like that lasered off before a doctor has looked at it. If you're not sure whether it's changing, photograph it next to a ruler so you can compare later.
How Should You Use Sunscreen on Driving Days?
How Should You Use Sunscreen on Driving Days?
Following the AAD's advice, choose a broad-spectrum sunscreen (it protects against both UVA and UVB) with SPF 30 or higher, and use at least a teaspoon on your face. Reapply about every two hours, or sooner if you've been sweating.
On a long drive, it's easiest to tie this to your schedule: once before you leave and again at a rest stop two hours in. Don't forget your ear and the side of your neck on the window side.
Keep in mind that sunscreen won't erase spots you already have. It cuts down on new damage, so the payoff shows over months. Even if you treat existing spots, they tend to come back in the same place if the window-side exposure doesn't change.
Why Track Both Sides With Photos?
Why Track Both Sides With Photos?
You can only compare sides fairly with photos taken the same way. Use front-facing light, not a window, and take a straight-on shot plus both profiles. Repeat it three months later in the same spot, and you'll see for yourself what your sunscreen habit has changed.
If you're in Seoul and want STON Clinic in Myeongdong to take a look, include how many hours a day you drive, how many years you've been driving, which side you've noticed more spots on, and whether any spot has changed recently. A changing spot gets checked first, and spots and wrinkles are planned after that.
If this raised a question about your own skin
Ask a questionReferences
- UVA passes through window glass and causes wrinkles and spots; how to choose sunscreen — American Academy of Dermatology — American Academy of Dermatology
- UVA blocking by windshields and side windows in 29 cars — JAMA Ophthalmol, 2016 — PubMed Central
- UV blocking by windows in 34 gas, hybrid, and electric vehicles — Arch Dermatol Res, 2025 — PubMed Central
- Skin cancers found more often on the left side — J Am Acad Dermatol, 2010 — PubMed Central
- Sun damage on one side of the face — N Engl J Med, 2012 — PubMed Central
- ABCDE warning signs of melanoma — American Academy of Dermatology — American Academy of Dermatology
Frequently asked questions
Q. Is it true that skin cancer is more common on the left side?
A. One study points that way. In 2010 U.S. skin cancer records, 52.6% were on the left and 47.4% on the right, with a clearer difference in men. Of 42 melanomas in situ, 31 (74%) were on the left. It's a single referral center's data, so it doesn't apply to everyone.
Q. Am I protected sitting in the passenger seat or the back?
A. Not necessarily. Side windows tend to block less UVA than the windshield. In the 2025 study of 34 cars, most windshields blocked UVA well, but protection from side windows wasn't consistent for drivers or other passengers.
Q. Do newer cars block more UV?
A. Model year alone isn't a reliable guide. In the 2025 study, mileage, not model year, was linked to UVA blocking at the driver's window, and in the 2016 study side windows ranged from 44% to 96% across cars. A sunscreen habit is safer than guessing from the car.
Q. How much sunscreen should I put on my face?
A. The AAD recommends at least a teaspoon for your face, and about an ounce (roughly a shot glass) for your whole body. If you use less, you won't get the SPF printed on the label, so apply in thin layers but make sure you use the full amount.
Jangju Kim Senior Director
JANGJU KIM
Dr. Jangju Kim is a clinic director at STON Clinic, LOTTE HOTEL in Myeongdong.
Career / Education
- 현) 스톤클리닉 명동 롯데호텔 원장
- 경희대학교 의과대학 졸업
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