Do You Need Sunscreen Indoors and in Winter?

Protection every day, in every season.

Imagine a cloudy winter day spent between a desk by the window and errands in the car.

You don't feel the sun's heat, so you wonder: why wear sunscreen today?

The answer is that heat is one thing, and UV rays are another.

In this article we answer:

• Do UV rays pass through windows?
• Do clouds protect your skin?
• When is sunscreen necessary at home?
• How do I use it properly?

Let's explore the science behind year-round sunscreen.

1. What's the difference between UVA and UVB?

UVB: mainly responsible for sunburn, and contributes to ageing.

UVA: penetrates deeper into the skin, is linked to tanning and signs of ageing, and can cause genetic damage in the cells where most skin cancers start.

The takeaway: No sunburn doesn't mean no damage.

2. Do UV rays pass through windows?

The Skin Cancer Foundation says window glass blocks most UVB, but UVA passes through it all year round.

So you may not burn by the window, but your skin is still exposed to the rays linked to ageing.

The takeaway: Glass reduces burning, but it doesn't stop UVA.

3. What about the car?

• Windscreen: laminated glass, usually treated to block some UVA.
• Side and rear windows and sunroof: tempered glass, which doesn't block UVA effectively.

The foundation cites a published case of a truck driver who worked for 28 years and had markedly more wrinkling and damage on the side of his face next to the window than on the other side.

The takeaway: Daily car journeys are reason enough to wear sunscreen.

4. Do clouds protect your skin?

Not fully. The American Academy of Dermatology reports that up to 80% of harmful UV rays can pass through clouds.

It adds that water, sand and snow also reflect UV rays.

The takeaway: A cloudy day is not a UV-free day.

5. Do you need sunscreen at home?

It depends on your day:

• Hours beside a sunny window: yes, because UVA passes through glass.
• Short trips to the car or the yard: yes, because daily minutes add up.
• A windowless room all day: the need may be lower, but a daily habit is easier to keep.

As for screen light, evidence on its effect on the skin is still limited.

The takeaway: If your day includes a window or a car, sunscreen makes sense.

6. Sunscreen in winter

Lower temperatures don't mean UV rays disappear, because we don't feel them as heat.

The AAD notes that sun protection is often neglected in winter and advises keeping it up all year.

The takeaway: Cold is a feeling; UV rays are a constant fact.

7. How to use sunscreen properly

Following the American Academy of Dermatology's advice:

1. Choose a broad-spectrum sunscreen with SPF 30 or higher.
2. Apply it to all exposed skin.
3. Reapply every two hours or after sweating.
4. Seek shade, especially between 10 am and 2 pm.
5. Use protective clothing, a hat and sunglasses.

An easy tip: if your shadow is shorter than you, you're under the strongest rays.

The takeaway: Sunscreen is part of a protection plan, not the whole plan.

8. Mineral or chemical sunscreen?

Type	Common filters	Best for
Mineral (physical)	Zinc oxide and/or titanium dioxide	Sensitive skin
Chemical	Such as avobenzone and octocrylene	Anyone who prefers a light, sheer texture

The AAD recommends mineral sunscreen for people with sensitive skin.

The takeaway: The best sunscreen is the one you actually wear every day.

9. Common myths

Myth 1: I don't need sunscreen on cloudy days. Not true. Up to 80% of harmful rays can pass through clouds.

Myth 2: Glass protects me completely. Not true. It blocks most UVB but lets UVA through.

Myth 3: Darker skin doesn't need sunscreen. Not true. UV affects all skin tones and can worsen pigmentation.

Myth 4: One application in the morning lasts all day. Not if you're outdoors. Reapply every two hours or after sweating.

10. Evidence vs marketing

Claim	What it really means
"All-day protection"	The AAD advises reapplying every two hours
"Broad spectrum"	Protects against UVA and UVB, which is what you need
"High SPF"	Doesn't replace applying enough and reapplying

No heat ≠ no UV

Higher SPF ≠ less reapplying

11. Sunscreen in Saudi Arabia: why this matters

The sun in most of the Kingdom is strong even on mild days, and winter is the season for desert outings, outdoor activities and walks.

Sand reflects UV, and long car journeys are part of daily life.

The AAD also warns that exposing sunscreen to extreme heat reduces its effectiveness, so don't leave it in the car.

Before buying, check that the product is registered with the Saudi Food and Drug Authority (SFDA).

The takeaway: Our winter is sunny, so sunscreen comes along on every desert trip.

12. How to choose your daily sunscreen: six questions

1. Is it broad spectrum (UVA and UVB)?
2. Is it SPF 30 or higher?
3. Is it water-resistant if you sweat or are active outdoors?
4. Is the texture comfortable enough to wear every day?
5. Is it within its expiry date?
6. Is the product registered with the SFDA?

13. Five evidence-based habits

1. Make sunscreen the last step of your morning routine every day.
2. Reapply every two hours when you're outdoors.
3. Don't forget your neck, ears and the backs of your hands.
4. Seek shade between 10 am and 2 pm.
5. Keep sunscreen away from extreme heat.

14. FAQs

Do I need sunscreen if I don't leave the house? If you're near sunny windows, yes, because UVA passes through glass.

Should I reapply indoors? Reapplying every two hours matters most outdoors or when sweating; indoors it depends on how much window exposure you get.

Is makeup with SPF enough? Usually you don't apply enough of it for the stated protection, so a separate sunscreen underneath is better.

Does darker skin need sunscreen? Yes, UV affects all skin tones.

Do I need sunscreen in the car? Yes, especially because side windows don't block UVA effectively.

Does sunscreen expire? Yes. Check the expiry date and avoid exposing it to extreme heat or cold.

Does screen light affect the skin? The evidence is still limited; protection from the sun itself matters most.

Sunscreen before or after makeup? After moisturiser and before makeup, as the last skincare step in the morning.

The Avnzor takeaway

UV rays don't take a winter break, and they don't stop at the window or car glass.

A broad-spectrum SPF 30+ sunscreen every morning, reapplied when you go out, is the simplest investment in your skin.

At Avnzor, we believe daily protection is the foundation of every successful routine.

Protection every day, in every season.

Discover sunscreens at Avnzor, with free delivery and no minimum order.

Disclaimer: This article is for general education and is not a substitute for advice from a doctor or pharmacist. Speak to a professional if you have a known sunscreen allergy or a skin condition, take medication, or are pregnant or breastfeeding. Patch test any new product before use. Sunscreen should not be used on babies under 6 months without medical advice.