Dr. Nate
@doctor.nate on TikTok
- Joined
- Feb 13, 2026
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Why does the sun age your skin?
Light from the sun contains ultraviolet radiation (UVR) [1]. UVR damages your DNA, increases proinflammatory cytokines and reactive oxygen species, upregulates enzymes that degrade the collagen in your skin, and directly damages your DNA [2-4]. This leads to the negative effects associated with excessive sun exposure such as skin cancer, sagging skin, wrinkles, and hyperpigmentation [2, 3].
Other wavelengths besides ultraviolet radiation also contribute to photoaging, but I will focus on UVR for simplicity since it is the main contributor [2].
What does this have to do with windows?
UVR can be categorized into UVA, UVB, and UVC rays. UVC rays are absorbed by the ozone layer, so they aren’t much of a concern [2]. UVB rays are blocked by glass, so when you are indoors they don’t pose much of a threat either. In contrast, UVA rays can pass through standard glass types and damage your skin even when you are indoors [5]. How much UVA passes through depends on the type of glass. Very little UVA passes through your car windshield because windshields are made with laminated glass (to prevent it from shattering and cutting your face open in a crash) [6, 7]. Laminated glass is very good at blocking UVA rays, whereas regular tempered glass (which the side windows of your car are probably made of) do a poor job [5].
How can I protect myself?
You can apply UV blocking films to your home’s windows, or replace them with laminated glass [6]. You can also wear sunscreen even when indoors. I use a Zinc Oxide mineral sunscreen since it’s superior at blocking UVA rays compared to Titanium Dioxide sunscreens, and it’s also better for acne [8, 9]. However, I usually don’t use this sunscreen inside my house. I don’t need to because I just block my windows. I typically use aluminum foil or paper. I don’t like curtains since they’re expensive and they let light in through the side gaps between the curtain and the wall. This isn’t a big deal for skin photoaging, but the light is enough to wake me up when l’m trying to sleep.
Light from the sun contains ultraviolet radiation (UVR) [1]. UVR damages your DNA, increases proinflammatory cytokines and reactive oxygen species, upregulates enzymes that degrade the collagen in your skin, and directly damages your DNA [2-4]. This leads to the negative effects associated with excessive sun exposure such as skin cancer, sagging skin, wrinkles, and hyperpigmentation [2, 3].
Other wavelengths besides ultraviolet radiation also contribute to photoaging, but I will focus on UVR for simplicity since it is the main contributor [2].
What does this have to do with windows?
UVR can be categorized into UVA, UVB, and UVC rays. UVC rays are absorbed by the ozone layer, so they aren’t much of a concern [2]. UVB rays are blocked by glass, so when you are indoors they don’t pose much of a threat either. In contrast, UVA rays can pass through standard glass types and damage your skin even when you are indoors [5]. How much UVA passes through depends on the type of glass. Very little UVA passes through your car windshield because windshields are made with laminated glass (to prevent it from shattering and cutting your face open in a crash) [6, 7]. Laminated glass is very good at blocking UVA rays, whereas regular tempered glass (which the side windows of your car are probably made of) do a poor job [5].
How can I protect myself?
You can apply UV blocking films to your home’s windows, or replace them with laminated glass [6]. You can also wear sunscreen even when indoors. I use a Zinc Oxide mineral sunscreen since it’s superior at blocking UVA rays compared to Titanium Dioxide sunscreens, and it’s also better for acne [8, 9]. However, I usually don’t use this sunscreen inside my house. I don’t need to because I just block my windows. I typically use aluminum foil or paper. I don’t like curtains since they’re expensive and they let light in through the side gaps between the curtain and the wall. This isn’t a big deal for skin photoaging, but the light is enough to wake me up when l’m trying to sleep.
- Widel, M., Krzywon, A., Gajda, K., Skonieczna, M., & Rzeszowska-Wolny, J. (2014). Induction of bystander effects by UVA, UVB, and UVC radiation in human fibroblasts and the implication of reactive oxygen species. Free Radical Biology and Medicine, 68, 278-287.
- Kaddurah, H., Braunberger, T. L., Vellaichamy, G., Nahhas, A. F., Lim, H. W., & Hamzavi, I. H. (2018). The impact of sunlight on skin aging. Current Geriatrics Reports, 7(4), 228-237.
- Guan, L. L., Lim, H. W., & Mohammad, T. F. (2021). Sunscreens and photoaging: a review of current literature. American journal of clinical dermatology, 22(6), 819-828.
- Boo, Y. C. (2020). Emerging strategies to protect the skin from ultraviolet rays using plant-derived materials. Antioxidants, 9(7), 637.
- Tuchinda, C., Srivannaboon, S., & Lim, H. W. (2006). Photoprotection by window glass, automobile glass, and sunglasses. Journal of the American Academy of Dermatology, 54(5), 845-854.
- Almutawa, F., Vandal, R., Wang, S. Q., & Lim, H. W. (2013). Current status of photoprotection by window glass, automobile glass, window films, and sunglasses. Photodermatology, photoimmunology & photomedicine, 29(2), 65-72.
- Chen, S., Zang, M., Wang, D., Yoshimura, S., & Yamada, T. (2017). Numerical analysis of impact failure of automotive laminated glass: A review. Composites Part B: Engineering, 122, 47-60.
- Smijs, T. G., & Pavel, S. (2011). Titanium dioxide and zinc oxide nanoparticles in sunscreens: focus on their safety and effectiveness. Nanotechnology, science and applications, 95-112.
- Kim, M. H. (2016). Biological effects of zinc oxide nanoparticles on inflammation. Cellmed, 6(4), 23-1.
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