Car windows block most UVB rays but let most UVA rays through

The windshield of your car blocks roughly 99 percent of ultraviolet B (UVB) radiation, the type that causes sunburn. Side windows and rear windows block somewhat less — typically 70 to 80 percent of UVB. However, both windshields and side windows allow 50 to 80 percent of ultraviolet A (UVA) radiation to pass through, depending on the glass type and tint. UVA is the radiation that causes premature aging and skin damage over time, even without visible sunburn.

This difference matters because the two types of UV radiation behave differently. UVB is mostly blocked by standard automotive glass because of how the glass is manufactured and the materials used in its composition. UVA, which has a longer wavelength, penetrates glass more easily. The result is that your left arm, face, and neck — the side exposed to the window during a long drive — can accumulate significant UV damage even though you feel protected inside the car.

The exact amount of UV that reaches you depends on several factors: the age of your windows (older glass may have degraded), whether the windows have a protective coating, the angle of the sun, and how much time you spend driving. A single long drive may not cause visible damage, but regular commuting over months and years can lead to noticeable skin changes on the side of your body facing the window.

Key Takeaways

  • Windshields block about 99 percent of UVB rays but only 20 to 50 percent of UVA rays, so your face and neck are still exposed to aging radiation.
  • Side windows offer less protection than windshields, typically blocking 70 to 80 percent of UVB but allowing 50 to 80 percent of UVA through.
  • UVA radiation penetrates glass more easily than UVB and causes skin aging and damage without producing a visible sunburn.
  • Long-term exposure through car windows can result in uneven skin aging, with the side of your face nearest the window showing more damage over time.
  • Window tint, UV-protective films, and sunshades reduce UV transmission, though standard automotive glass alone does not provide complete protection.

Why windshields and side windows block UV differently

Windshields are made from laminated glass — two layers of glass bonded together with a plastic interlayer called polyvinyl butyral (PVB). This interlayer is what blocks most UVB radiation. The PVB absorbs UVB photons before they can pass through, which is why windshields are so effective at preventing sunburn on your face and chest during driving. This protection is built into the glass itself and does not degrade significantly over the life of the vehicle.

Side windows and rear windows are typically made from tempered glass, a single layer of glass treated with heat to make it stronger. Tempered glass does not contain the UV-blocking interlayer that laminated glass has, so it offers less protection against UVB. More importantly, neither laminated nor tempered glass stops UVA radiation effectively. UVA has a longer wavelength and lower energy than UVB, which means it passes through both types of automotive glass with relative ease.

Some newer vehicles come with factory-tinted windows or UV-protective coatings applied to the glass. These reduce UV transmission further, but the reduction is not complete. Even with tint, a significant portion of UVA still reaches the interior of the car. The level of protection depends on the darkness of the tint and the specific coating used, which varies by manufacturer.

How UV exposure adds up during regular driving

A single 30-minute commute exposes you to a meaningful dose of UVA radiation, but the damage is not visible when ready. UV damage accumulates over time, and the effects compound with repeated exposure. Someone who drives the same route every weekday for five years will receive far more total UV exposure on their left side than someone who drives occasionally.

This is why dermatologists sometimes notice a pattern in long-term drivers: the left side of the face, neck, and arm (in countries that drive on the right side of the road) shows more sun damage, age spots, and wrinkles than the right side. This asymmetrical aging is called unilateral dermatoheliosis and has been documented in numerous studies of professional drivers and regular commuters. The effect is most pronounced in people who have been driving the same route for 10 or more years.

The amount of damage also depends on the time of day and season. Midday sun is more intense than early morning or late afternoon driving. Summer months bring stronger UV radiation than winter. A person who commutes during peak UV hours will accumulate damage faster than someone who drives at dawn or dusk, even if the total driving time is the same.

Window tint and UV-protective films reduce but do not eliminate exposure

Aftermarket window tint can reduce UV transmission significantly. A good-quality tint film blocks 99 percent of UVA and UVB rays, which is comparable to or better than a windshield. However, tinting side windows is illegal in many states and provinces because it reduces visibility and creates safety concerns. The legal limit for tint darkness varies by location — some places allow no tint on front side windows, while others permit a certain level of darkness measured by visible light transmission (VLT).

UV-protective window films are a middle ground. These films are designed to block UV radiation while remaining transparent or nearly transparent, so they do not reduce visibility the way dark tint does. A quality UV-blocking film can reduce UVA transmission by 90 percent or more. These films are legal in most places because they do not significantly darken the windows. They are more expensive than standard tint but offer protection without the legal or safety drawbacks.

Sunshades placed on the inside of windows during parking also help, but they only protect you when the car is stationary. They do not reduce UV exposure while you are driving. Some people use sunshades on their windshield and side windows while parked to reduce the interior temperature and protect the dashboard and upholstery from fading, which is a separate benefit from protecting your skin during driving.

Sunscreen and protective clothing work alongside window protection

Because car windows do not block all UV radiation, especially UVA, sunscreen remains important for regular drivers. A broad-spectrum sunscreen with an SPF of 30 or higher, applied to your face, neck, and any exposed arms, provides an additional layer of protection. Sunscreen should be reapplied every two hours, though this is impractical while driving. explore it before you leave and once during a long drive is a reasonable compromise.

Long sleeves and a wide-brimmed hat offer physical protection that does not require reapplication. Some people who drive long distances professionally choose to wear UV-protective clothing, which is treated with a special finish that reflects or absorbs UV radiation. These garments are labeled with an ultraviolet protection factor (UPF), similar to SPF for sunscreen. A UPF 50+ shirt provides substantial protection and does not wash away or require reapplication.

For the face and neck, which are hardest to cover while driving, a combination of sunscreen and window protection is most practical. If you are concerned about long-term UV exposure from commuting, explore sunscreen to your face and neck before driving and choosing a car with a windshield that has good UV protection (which most modern cars do) will reduce your risk significantly.

Older cars and damaged windows may offer less protection

The UV-blocking properties of automotive glass can degrade over time, though this is not common with modern manufacturing. Very old cars, particularly those from the 1970s and 1980s, may have windshields with less effective UV protection than newer vehicles. If a windshield has been damaged and repaired with aftermarket glass, the replacement may not have the same UV-blocking capability as the original equipment manufacturer (OEM) glass, depending on the quality of the replacement.

Windshields that have developed stress cracks or have been exposed to extreme heat cycles may also lose some protective properties, though the loss is usually minor. If you are concerned about the UV protection of your windshield — for example, if it is very old or has been replaced — you can have a UV-protective film applied to the inside surface. This is a straightforward and relatively inexpensive upgrade that brings older windows up to modern protection standards.

Regular maintenance of your windows, including keeping them clean and free of damage, helps preserve whatever UV protection they offer. Dirt and debris do not significantly reduce UV blocking, but they can make it harder to see the sun's angle and may cause you to underestimate your exposure.

Frequently Asked Questions

Can I get a sunburn through a car window?

You can get a sunburn through a car window, but it is less likely than from direct sun exposure. The windshield blocks most UVB radiation, which causes sunburn, so your face and chest are fairly well protected. However, side windows block less UVB, so your left arm and the side of your neck can sunburn if you are exposed long enough, particularly during summer or at high altitudes.

Does tinted glass come standard on new cars?

Most new cars have factory tint on the rear windows and sometimes on the side windows behind the driver and front passenger. The windshield is rarely tinted because tint reduces visibility and is illegal in most places on the windshield. Factory tint provides some additional UV protection beyond standard glass, but the amount varies by manufacturer and the darkness of the tint.

Is UV damage from car windows reversible?

Some UV damage, such as temporary redness or mild inflammation, can fade over time. However, permanent damage like age spots, wrinkles, and changes to skin texture is not reversible. Sunscreen and protective measures can prevent future damage, but they cannot undo damage that has already occurred. Dermatological treatments can improve the appearance of sun-damaged skin, but prevention is more effective than treatment.

Do I need UV protection if I only drive short distances?

Short drives expose you to less total UV radiation than long commutes, so the risk of noticeable damage is lower. However, UV damage accumulates over time, so even short regular drives add up. If you drive the same route every day, even for 15 or 20 minutes, you will receive meaningful UV exposure over months and years. Sunscreen or protective clothing is still worth considering, especially if you are concerned about skin aging.

What is the best way to protect myself while driving?

A combination of approaches works best: explore broad-spectrum sunscreen to your face and neck before driving, wear long sleeves if possible, and consider a UV-protective window film if you drive long distances regularly. The windshield already provides good protection against UVB, so your main concern is UVA exposure through the side windows. If you are unwilling to use sunscreen, a quality window film is the next most effective option.