Sun Protection: Should You Wear Sunscreen Indoors?

You probably know that sunscreen is a must regardless of the weather. As the harmful UV rays can still penetrate through the clouds, they can reach and get absorbed by your skin, potentially causing damage. But what about indoors or at home? Do you still need to wear sunscreen even though you’re not directly exposed to the sun? 

Before we answer this question, let us first discuss in brief the types of ultraviolet (UV) light or rays. There are three classifications: UVA, UVB, and UVC. 

• UVA rays – have the longest wavelengths and account for about 95% of sun rays that reach the earth. They can penetrate the middle layer of the skin (dermis) and cause damage to skin cells. UVA rays can contribute to premature aging and are associated with certain types of cancer. 
• UVB rays – have shorter wavelengths than UVA and only account for 5% of UV rays that can reach the ground. These rays affect the epidermis or the outermost layer of the skin. They can directly damage your skin’s DNA and cause most skin cancers. Prolonged exposure to UVB rays can result in sunburn.
• UVC rays – have the shortest wavelength and don’t reach the earth’s surface (the atmosphere completely filters these rays). They are mostly available through artificial sources (welding torch, mercury lamps). UVC rays are harmless and not considered a risk factor for skin cancer. 

Can glass windows keep out UV rays? 

A standard or regular window glass can filter out mostly 100% of UVB light, but will let UVA pass through. Therefore, some UV rays can still enter your house and potentially affect your skin. This is particularly true for UVA rays, which are known to suppress the immune system and contribute to premature aging of the skin. 

But what about window films? Solar window films can help, as they help block UVA rays and reflect some heat, which may keep your home cooler. They are also easy to buy and install, but just make sure that the one you’re installing is a solar film. Not all window films can stop UVA rays from penetrating through the windows. 

Is there still UV exposure indoors?

The risk of UV exposure indoors is low, but wearing SPF even when your inside is not a bad idea. This is especially true if you spend a lot of time sitting near a window that receives a lot of sunlight. As previously mentioned, some UV rays can still penetrate glass windows (at home, in your office, and inside your car).

This is why sun protection is not only a must at times when you see and feel the sun shining down. There are lots of sneaky situations where UV rays can hit and reach your skin. Working near a window (anywhere within several feet) is one of the  most common examples, as about 50% of UVA rays can penetrate through glass. 

How about reapplication? 

The general recommendation is to reapply sunscreen every two hours, particularly when you’re sweating or after swimming. Reapplication, however, is unnecessary if you’re indoors and sit away from windows. If you, on the other hand, sit in a room or near a window that receives lots of sunlight, you may need to reapply (sunscreen indoors) every 4 hours.

Just be mindful when you choose to go outside for whatever. Whether you’re running quick errands or going for a short stroll, the UV rays can still damage your skin. In cases like this, wearing sunscreen is necessary. Other sun protection measures such as wearing sunglasses, protective clothing, and a brimmed hat can help, especially during peak hours. 

Which sunscreen Indoors should I use? 

Choose a broad-spectrum sunscreen with an SPF (sun protection factor) of at least 30. It is also important to choose a product that won’t clog your pores, especially if you have oily or acne-prone skin. Fragrance- and oil-free formulations, as well as those labeled-non-comedogenic, are good options. 

Check out our previous post to know some features to look for when buying or choosing a face sunscreen.

At Cutis Medical Laser Clinics, we have Dr. Sylvia’s Clear Defense SPF 45 with Broad Spectrum. This formula has zinc oxide, an active ingredient that blocks UVA and UVB radiation, and niacinamide, for a smoother and clearer complexion. It is also fast-absorbing and lightweight (leaves no residue), making it ideal for normal, oily, and sensitive skin types.

Benefits include:

• Prevents UVA/UVB and infrared damage
• Helps improve the look of lines and wrinkles
• Helps increase skin firmness and elasticity
• Reduces redness, blotchiness, and hyperpigmentation  

Browse through our website today for more skincare tips and product recommendations. Don’t hesitate to contact Cutis Medical Laser Clinics in Singapore today and book a consultation with our aesthetic doctor for your face, body, sunscreen indoors, and skin concerns.