Should I Wear Sunscreen Indoors?

by Claudia Christin on Mar 22, 2023

should i wear spf indoors?

The sun’s far from our eyesight, we are indoors and the sun does not shine on top of our head directly. Has it ever come to your mind whether it's the perfect time to skip on your sunscreen. It’s normal for anyone to think so, having the thoughts that they can save so much money to not wear sunscreen on cloudy days or indoors! Oh well, but it’s not the case for everyone and we are going to dig in deeper on the pros and cons of skipping your sunscreen while you’re indoors.

First, we should clearly understand that the sun is the number one risk factor of premature aging and sunscreen protects us not from the aesthetic side of it, but it is also protecting us from prolonged exposure risk for skin cancer. Let’s answer each one of your commonly asked questions related to sunscreen and being indoors:

UV rays can still pass through the clouds, and the window as well, especially the UVA rays.

Q: “If the cloud is out, sun is hiding, and we are indoors, 

the UV rays will have no chance to reach us, right?”

Answer: Actually, the UV rays can still pass through the clouds, and it is still able to pass through the window as well, especially the UVA rays. 50 - 60% of the UVA can pass through and lead to premature aging. However, the number may differ depending on the thickness or the type of technology the embedded on the window, but most of them can’t entirely filter through the UV rays.

If you are not sure whether to use spf or not, check the weather apps to see the UV index

If you are not sure whether to use sunscreen or not, check the weather apps to see the UV index! If the UV index number is shown to be around 1-3 you can skip sunscreen (this applies even when you’re outdoor).. However, if the UV index number is shown to be above 3, your skin definitely would thank you if you wear sunscreen indoors, especially if you are doing activities near the window.

It is also advised to pay attention to often forgotten body part in times like this, such as hands, neck, and decolletage. Since the hand, neck and decolletage are often neglected even though they are exposed to the sun as much as our face, many experience premature aging on those areas sooner than the other parts of skin they take care of.

glass windows do filter out UVB rays but can not filter out UVA rays

Q: “I don’t even notice my skin being darker if I don’t wear sunscreen indoors. What’s the importance of wearing sunscreen when I’m indoors then?”

Answer: Because actually, glass windows do filter out UVB rays – which plays a huge role in burning our skin, hence why we do not feel our skin to be darker if we do not wear sunscreen indoors. However, glass windows can not filter out UVA rays - which plays a huge role in aging and hyperpigmentation. The impact of UVA exposure may not show right away at the moment, but it gradually builds up and as time goes by, you’ll notice your skin aging earlier than it should. The UVA rays penetrate to the deeper layer of your skin and the damage is just as harmful to your skin. This is why you are still recommended to use sunscreen even indoors.

different types of UV rays: UVA = aging, UVB = burning. Both causes skin damage





Cause skin damage 


Longer wavelength and reaches to deeper layer of our skin

Penetrate through clouds 

Shorter wavelength and are responsible for surface damage 

Responsible for signs of aging and accumulative damage 

Causes immediate sunburn and other skin damage 

Can penetrate through glass 

Can’t penetrate through glass 

water resistant sunscreen

Q: “What if I’m entirely indoor without any single bit of sun exposure 

(I'll close the blind and all)”

Answer: If you’re entirely indoors with no sun exposure at all through the windows, of course you can skip the sunscreen without having to be worried about it. However, most of the time you may have to get yourself out and expose yourself to a little bit of sun, either if it’s taking your takeaway or doing a little grocery shopping. Even when you’re inside your car, the UVA rays can still cause damage to your skin cumulatively.

chemical vs. physical sunscreen

Q: “Okay, I’ll use sunscreen even indoors from now on. 

But do I need to reapply?”

Answer: Reapplying every 3-4 hours is not a must because we are less likely to be sweating indoors so it should be still staying in place and not be erased easily. But it doesn’t mean that you are not allowed to reapply, it is still best to reapply especially if you are next to the window, but maybe the amount of time you’re reapplying shouldn’t be as often as if you are outdoors.

Tips when you’re indoor and you want to reapply: 

Reapply 15- 30 minutes before noon (12 pm) with added physical protection since it is the time of highest UV intensity (index).

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