Sun Protection

Do You Need Sunscreen Indoors? The Science of Indoor UV Exposure

Do you need sunscreen indoors? Research shows ordinary glass transmits up to 74% of UVA rays. Learn when indoor sun protection matters and when you can skip it.

Do You Need Sunscreen Indoors? The Science of Indoor UV Exposure

A 2009 experimental study in Photodermatology, Photoimmunology & Photomedicine found that ordinary window glass transmits 74.3% of UVA radiation while completely blocking UVB. A separate 2013 review confirmed that car side windows allow up to 79% of UVA through. These numbers challenge the assumption that being indoors means being protected — but the full picture is more nuanced than social media suggests.

Quick Summary:

  • Standard window glass blocks all UVB but allows up to 74% of aging UVA radiation through
  • Car windshields (laminated glass) block nearly 100% of UVA — side windows do not
  • Indoor sunscreen is most important if you sit near windows with direct sunlight for extended periods
  • Blue light from screens is not a significant skin concern at normal usage distances
  • If you spend most of your day away from windows, indoor sunscreen is optional

How UV Penetrates Windows

Understanding which UV rays get through glass helps you make informed decisions about indoor protection.

UVB rays (290-320nm) are responsible for sunburn and are completely blocked by all types of glass. If you're indoors, you will not burn from window-transmitted sunlight.

UVA rays (320-400nm) cause photoaging, pigmentation, and contribute to skin cancer risk. These pass through glass at alarming rates:

  • Ordinary window glass: Transmits 74.3% of UVA
  • Tempered glass (car side/back windows): Transmits 71.6% of UVA
  • Green-tinted glass: Transmits less UVA than clear glass but still significant amounts
  • Laminated glass (car windshields): Blocks virtually 100% of UVA

The 2013 review noted that even reflective, tinted, coated, or double-paned architectural glass can transmit up to 50% of UVA. The only glass type that provides near-complete protection is laminated glass, which sandwiches a UV-absorbing plastic layer between two glass sheets.

When Indoor Sunscreen Actually Matters

Not everyone needs sunscreen inside. Here's when it genuinely makes a difference:

You sit near a window with direct sunlight. If sunlight falls on your skin through a window for more than 30 minutes daily, you're receiving meaningful UVA exposure. A 2013 study found that the average person spends 80-96 minutes per day in a car — that's significant cumulative UVA through side windows.

You drive frequently. Car side windows transmit the most UVA of any common glass type. Research on skin cancer distribution shows higher rates on the left side of the body in countries where drivers sit on the left — consistent with chronic UVA exposure through driver's side windows.

You have a photosensitivity condition. Lupus, polymorphous light eruption, and certain medication-induced photosensitivities can be triggered by UVA that passes through windows.

You're using photosensitizing treatments. Retinoids, certain AHAs, and some prescription medications increase your skin's UV vulnerability. If you apply these and then sit in window-lit spaces, indoor protection is wise.

You're treating hyperpigmentation. UVA stimulates melanin production and can undo progress from depigmenting treatments. If you're actively treating dark spots or melasma, indoor UVA exposure near windows can set you back.

Sunscreen by window with sunlight

When Indoor Sunscreen Is Unnecessary

You're in a room without direct sunlight. Interior rooms, basement offices, or spaces with blackout curtains receive negligible UV radiation. Sunscreen provides no benefit in these settings.

You're briefly passing through sunny spaces. Walking through a sunlit hallway or spending a few minutes near a window doesn't deliver enough cumulative exposure to matter for most people.

You're far from windows. UV intensity decreases rapidly with distance from the glass. Sitting 10 feet from a window is dramatically different from sitting in direct window light.

You work under artificial lighting only. Standard fluorescent and LED lighting emit negligible UV radiation. The concern about office lighting and skin damage is largely a myth.

Verdict: Indoor sunscreen is a targeted recommendation, not a universal one. If you spend significant time near windows — especially in a car or at a window-facing desk — daily sunscreen makes sense. If your indoor time is mostly away from direct sunlight, save your sunscreen for when you go outside.

The Blue Light Question

Social media has fueled anxiety about blue light (high-energy visible light) from screens causing skin aging. Here's what the research actually says.

A 2023 review in the Journal of Cosmetic Dermatology found that blue light does cause DNA damage, photodamage to collagen and elastin, and hyperpigmentation in laboratory studies. Effects on pigmentation were more pronounced in darker skin tones.

However, context matters enormously. The intensity of blue light from a phone or computer screen is a tiny fraction of the blue light in sunlight. Holding a device just 10 centimeters from your skin reduces exposure 100-fold compared to direct contact. At normal usage distances, the practical significance for skin damage is minimal.

The evidence does not support wearing sunscreen specifically to protect against screen blue light. If you're already wearing sunscreen for window-transmitted UVA, it provides some blue light protection as well — iron oxide in tinted mineral sunscreens blocks visible light including blue wavelengths. But buying specialized "blue light" skincare products is not supported by current evidence.

Indoor sun protection product set

How to Protect Yourself Indoors

For Your Skin

If you sit near windows, a broad-spectrum sunscreen with UVA protection is the simplest solution. EltaMD UV Clear SPF 46 (around $40) provides strong UVA coverage in a lightweight formula suitable for daily indoor wear. For a budget option, Neutrogena Hydro Boost Water Gel Sunscreen SPF 50 (around $17) offers comfortable daily protection.

Apply in the morning as the final step of your skincare routine — you don't need to reapply every two hours indoors unless you're in continuous direct window light. See our sunscreen application guide for technique.

For Your Windows

UV-blocking window films are the most effective solution for reducing indoor UVA exposure across an entire room:

  • Clear UV-blocking film blocks up to 99.9% of UV radiation without changing the appearance of your windows
  • Tinted window film blocks UV while reducing glare and heat
  • UV-blocking treatments for car side windows are available from automotive tinting shops and address the highest-risk indoor UV scenario

These films are a one-time investment that protects everyone in the space without requiring daily sunscreen application indoors.

Antioxidants as a Complement

A daily vitamin C serum provides an additional layer of defense against UVA-generated free radicals. Vitamin C neutralizes reactive oxygen species that UVA produces in skin cells, complementing sunscreen's physical protection. Apply vitamin C before sunscreen in the morning.

For additional antioxidant support, niacinamide reduces UV-induced inflammation and supports DNA repair. CeraVe PM Facial Moisturizing Lotion (around $15) contains niacinamide and makes an excellent base layer under sunscreen.

Special Considerations

Working from home: If your desk faces a window, daily sunscreen is a smart habit. If you work in an interior room, it's unnecessary. Rearranging your workspace so you don't sit in direct window light is an even simpler solution.

Driving: Your face, neck, and left arm/hand (in left-side driving countries) receive the most UVA exposure. Apply sunscreen to these areas daily if you commute. Better yet, ask about UV-blocking tint for your side windows.

Airplanes: Aircraft windows transmit UVA at higher intensities due to altitude. Window seat passengers on long flights receive meaningful UV exposure. Apply sunscreen before flying and close the shade when possible. See our sunscreen guide for travel tips.

Frequently Asked Questions

Do I need sunscreen if I work from home?

Only if you sit near a window with direct sunlight. If your home office is in an interior room or has curtains blocking direct light, indoor sunscreen provides no benefit beyond what you'd get from wearing it when you step outside.

Can you get a tan through a window?

You won't burn through glass (UVB is blocked), but UVA penetrates glass and stimulates melanin production. Over time, regular window-adjacent UV exposure can darken your skin, worsen melasma, and contribute to photoaging — without the visible warning of a sunburn.

Does window tint block UV?

Standard automotive tint reduces visible light but doesn't necessarily block UV unless specifically rated for UV protection. Request UV-blocking tint that meets or exceeds 99% UV rejection. Architectural window films marketed for UV protection are the most reliable option for home windows.

Is blue light from screens aging my skin?

Current evidence suggests the clinical impact is negligible at normal usage distances. The blue light from your phone is orders of magnitude less intense than blue light in sunlight. Wearing sunscreen to protect against screen light specifically is not necessary.

How much UVA comes through office windows?

Standard office glass transmits 50-74% of UVA depending on the type. However, your actual exposure depends on distance from the window, time spent in direct light, and whether the window faces the sun. Interior desks away from windows receive minimal UV.

Should I reapply sunscreen while indoors?

If you're in continuous direct window light, reapply every two hours as you would outdoors. If you're simply in a room with some ambient window light, your morning application is sufficient. Indoor UV exposure is lower intensity than direct outdoor exposure.

Do curtains and blinds block UV?

Opaque curtains and closed blinds block virtually all UV. Sheer curtains reduce but don't eliminate UVA transmission — they typically block 50-70% depending on fabric weight and color. If UV protection is a concern, closed blinds or blackout curtains are the most effective textile solution.

Can LED lights damage your skin?

No. Standard LED office lighting and home lighting emit negligible UV radiation. The occasional fluorescent tube may emit trace amounts, but well below any threshold that would cause skin damage. Artificial lighting is not a skincare concern.

Is indoor UV exposure a skin cancer risk?

Chronic UVA exposure through windows does contribute to cumulative UV damage, which is a risk factor for skin cancer over decades. The risk is most significant for people who sit in direct window light daily for years — particularly drivers. For occasional window-adjacent exposure, the risk is minimal.

What's the best sunscreen for daily indoor use?

Choose a lightweight, broad-spectrum formula you'll actually wear every day without thinking about it. Mineral options like EltaMD UV Clear or La Roche-Posay Anthelios Mineral (around $35) feel comfortable enough for all-day indoor wear. The best indoor sunscreen is one you won't skip.

Should children wear sunscreen indoors?

Not routinely. Children benefit more from limiting direct sun exposure through window management (blinds, UV film) than from daily indoor sunscreen application. If a child's play area or study space receives direct window sunlight for extended periods, either move the activity or apply sunscreen.

The Bottom Line

Indoor sun protection is situational, not universal. If you spend significant time near windows — particularly while driving or at a window-facing desk — daily sunscreen and UV-blocking window film are worthwhile investments. If your indoor life mostly keeps you away from direct sunlight, focus your sunscreen efforts on when you go outside.

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