Window Tint Guide: Understand
Window Tint and Skin Protection: UV Through Car Windows
Most people assume that being inside a car means being out of the sun. For sunburn, that is mostly true. For the deeper-reaching UVA rays associated with skin cancer and cataracts, it is not, and the side windows are the weak point.
If you spend an hour a day on I-85 or US-76 with the sun on your left arm, this is worth understanding. Window film can close most of that gap, but it is one layer of protection, not the whole plan.
The short answer
Car glass blocks most UVB, but side windows let through much more UVA than windshields. A 2016 JAMA Ophthalmology study of 29 cars found windshields blocked 96% of UVA on average, while driver's side windows averaged 71% and ranged from 44% to 96%. Quality window film closes most of that gap: the Skin Cancer Foundation's seal requires films to block 99% or more of UVA and UVB.
Key points
- UVB is largely filtered by glass; UVA passes through windows and reaches deeper into skin.
- Windshields are laminated and block most UVA; side, rear and sunroof glass is usually tempered and blocks far less.
- Research has found more skin cancers on the left side of the body in U.S. patients, consistent with driving exposure.
- Clear film can block UV as effectively as dark film, so UV protection does not require a dark shade.
- Film does nothing when the window is down or for time outside the car; sunscreen and clothing still matter.
UVA vs UVB
Why glass stops sunburn but not all skin damage
Ultraviolet light reaching the ground comes in two main bands. UVB affects the outer layers of skin and is the main cause of sunburn. UVA penetrates more deeply and, according to the Skin Cancer Foundation, accounts for up to 95% of the UV radiation reaching the earth.
The difference that matters in a car: UVB is filtered by window glass, but UVA can pass through windows and cloud cover. That is why you rarely sunburn through a car window yet can still accumulate UVA exposure on the side of your face, neck and arm that faces the glass, day after day.
The glass
Windshields and side windows are different glass
The Skin Cancer Foundation explains that front windshields are laminated glass, treated to shield drivers from some UVA, while the glass in side, back and sunroof windows is usually tempered and does not block UVA as effectively.
A 2016 study in JAMA Ophthalmology put numbers on it. Researchers measured UVA outside and behind the windshield and driver's side window of 29 cars from 15 manufacturers, model years 1990 to 2014. Windshields blocked an average of 96% of UVA, in a tight range of 95% to 98%. Side windows averaged 71%, with a wide range from 44% to 96%. Only 4 of the 29 cars had side windows blocking more than 90%.
That range is the point. You cannot tell by looking how well your side glass blocks UVA, and some cars let through more than half.
The evidence
What research says about driving and skin
In the United States, the driver sits on the left, and the left side of the body faces the side window. A study published in the Journal of the American Academy of Dermatology reviewed skin cancer patients referred to a Mohs surgery unit in 2004 and found more cancers on the left side than the right overall (52.6% versus 47.4%), with a stronger trend in men. For melanoma in situ, the difference was larger: 74% of cases were on the left.
The JAMA Ophthalmology authors wrote that lower UVA protection in side windows may in part explain reported higher rates of left-sided facial skin cancer and left-eye cataract. That is a possible explanation, not a proven cause, and the dermatology study was based on patients at one academic center. But the direction of the evidence is consistent.
Film
How much UV window film blocks
In LLumar's lineup, UV blocking does not depend on shade. LLumar rates its films to block up to 99% of UV rays, and its published spec sheet lists greater than 99% ultraviolet protection, over wavelengths of 300 to 380 nanometers, for every automotive film it shows, from a 5% charcoal film to an 87% clear UV film.
The Skin Cancer Foundation recommends UV window film for the driver and passenger side windows and sunroof, and awards its Seal of Recommendation to window films that provide data showing they block 99% or more of solar UVA and UVB. It notes that not every film is designed for UV protection, so look for products marketed as UV or solar window film.
Because UV protection is engineered into the film rather than coming from darkness, a nearly clear film can protect your skin as well as a dark one. That is useful if you want protection without changing the look of the car, and it means UV protection never requires going below South Carolina's 27% limit.
Priorities
Which windows matter most for skin
- Driver's side windowHighest priority
- It sits closest to your face, neck and left arm for every mile you drive. This is where the JAMA study found the weakest and most variable protection.
- Front passenger windowRegular passengers
- Same tempered glass and the same exposure for whoever rides there most, often a spouse or teenager.
- Rear side windowsChildren and long trips
- Kids in car seats sit right beside rear glass and cannot move out of the sun. Rear film protects them on every trip. Family car tint
- Sunroof or glass roofOften overlooked
- The Skin Cancer Foundation lists sunroofs alongside side windows as glass that does not block UVA effectively. Sunroof tint
- WindshieldAlready strong on UVA
- Laminated windshields averaged 96% UVA blocking in the study. In South Carolina, film is only allowed above the AS1 line anyway.
Limits
What window film does not do
- It does not protect you with the window down. Many people drive with the window cracked on a nice day, which removes the protection entirely.
- It does not cover the time you spend outside the car: walking across a parking lot, a day at Lake Hartwell or a ball game in Clemson.
- It does not replace sunscreen, clothing or shade for people with a history of skin cancer or high sensitivity. Ask your dermatologist what they recommend for driving.
- It does not make up for exposure you already have. Regular skin checks matter, especially for a spot on the side that faces the window.
- It is not a medical device. If you have a diagnosed photosensitive condition, South Carolina's medical exemption may allow darker film with an affidavit from a licensed physician or optometrist.
Practical
A sensible sun plan for drivers
Add UV-blocking film to the side windows
Start with the driver's side and front passenger window, then the rear sides if you carry children.
Pick the shade for looks and law, not UV
Light and dark films can both block more than 99% of UV, so choose the shade for privacy, glare and South Carolina's 27% limit.
Keep sunscreen in the car
For the left arm and face on long drives, especially with the window down.
Watch the left side
Mention any changing spot on the side that faces the window at your next skin check.
Add UV protection to the glass that needs it
LLumar rates its films to block up to 99% of UV rays. We offer LLumar Carbon and LLumar Ceramic, both computer cut for your vehicle, and check the legal shade first.
Common questions
Can you get sunburned through a car window?
Rarely. Sunburn is mainly caused by UVB, and window glass filters most UVB. But UVA passes through side windows much more freely, and UVA penetrates deeper into skin and is associated with skin cancer risk. So the absence of sunburn does not mean the absence of exposure, especially on long, sunny drives with your arm near the glass.
Do I need sunscreen when driving?
If your side windows are untreated, sunscreen on the face, neck and arms is a reasonable habit for long or frequent drives, since side glass blocked as little as 44% of UVA in one study. With quality UV film, the glass itself blocks almost all UV, but sunscreen still helps when the window is down and for time outside the car. Your dermatologist can advise for your skin.
Does dark tint block more UV than light tint?
Not necessarily. UV protection is engineered into the film; it does not come from how dark the film looks. On LLumar's published data, its films from 5% charcoal to an 87% clear UV film all list greater than 99% UV protection. Darkness changes visible light and glare; UV blocking depends on the product, so check the spec sheet.
Does the Skin Cancer Foundation recommend car window film?
The Skin Cancer Foundation recommends UV window film for car side windows and sunroofs as part of a sun protection plan. It awards a Seal of Recommendation to films with data showing they block 99% or more of UVA and UVB. It also stresses that film is one part of protection, alongside sunscreen, clothing and shade.
Sources
- Boxer Wachler BS, Assessment of Levels of Ultraviolet A Light Protection in Automobile Windshields and Side Windows, JAMA Ophthalmology 2016;134(7):772-775, PubMed (https://pubmed.ncbi.nlm.nih.gov/27258091/), accessed October 2026
- Butler ST, Fosko SW, Increased prevalence of left-sided skin cancers, Journal of the American Academy of Dermatology 2010;63(6):1006-1010, PubMed (https://pubmed.ncbi.nlm.nih.gov/20226568/), accessed October 2026
- UV Window Film and Tint, The Skin Cancer Foundation (https://www.skincancer.org/skin-cancer-prevention/sun-protection/uv-window-film/), accessed October 2026
- UV Radiation, The Skin Cancer Foundation (https://www.skincancer.org/risk-factors/uv-radiation/), accessed October 2026
- LLumar Window Film Performance Data (LL0116NAEN), Eastman Performance Films (https://www.llumar.com/content/dam/eastman/performance-films/llumar/documents/LL0116NAEN_AutoSpecs_screen.pdf), accessed October 2026
- Automotive Window Tint Frequently Asked Questions, LLumar (https://www.llumar.com/en/resources/automotive-window-tint-frequently-asked-questions/), accessed October 2026
- S.C. Code Ann. § 56-5-5015, South Carolina Legislature (https://www.scstatehouse.gov/code/t56c005.php), accessed October 2026
Prices on this page are The Auto Show’s published starting prices. Film ratings and warranty terms come from the manufacturer. This guide explains South Carolina law in plain words; it is not legal advice.