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#3 Blue Light, Another Sun Indoors!


What would happen if you went outside without wearing any sunscreen on a day with scorching sun, the temperature over 37°C, and heat shimmer on the road? “The skin will age faster.” “Melasma and blemishes will develop.” Just like what most people are aware of, excessive exposure to UV rays causes melasma, blemishes or even redness and a burning sensation on the skin. This is why we can easily find people wearing sunscreen as well as using a parasol, a hat, or sunglasses when there’s a heat wave alert across the country. There is also, however, another type of sunlight besides UV rays that people are discussing ways to avoid to delay aging. That is blue light.

Exposure to blue light is ever increasing with the changes of daily life caused by COVID-19, such as online learning aided by digital devices, watching Netflix through a monitor, and checking YouTube videos on a smartphone, etc. According to LBLL’s research on the life of women today, the exposure to blue light has increased by 1.7 times compared to the pre-pandemic era. This light generated from electric devices induces corneal damage and dry eye syndrome. It is also known to affect the body’s biorhythm and cause insomnia. What then is the potential for skin damage caused by blue light?

Blue light has the highest level of energy within the wavelength of visible light. Electronic devices are one of its sources, but a large portion of sunlight consists of blue light as well. Sunlight that reaches the earth is 3-5% UV rays, 42-43% visible light, and 52-55% infrared light. Blue light takes up 28% of the entire visible light spectrum.

While a great amount of blue light is emitted from sunlight as well as electronic devices, LBLL suggests that the next biggest source of this light is the fluorescent light, which helps us maintain our everyday life.

Environment Intensity(mW/cm2)
Sunlight (March) 0.5359
Sunlight (August) 0.8705
Fluorescent light 0.1074
Monitor 0.011
ipad 0.008
smartphone 0.004
TV 0.002

As a result of measuring the strength of blue light people are exposed to every hour, with office workers in their 20s to 40s, the strongest sources were sunlight > fluorescent light > monitor > tablet PC > smartphone > TV. This shows that fluorescent light releases a stronger light compared to monitors or smartphones, more than what people would imagine. There’s also another research finding that needs to be highlighted.

9h 14h 17h
Indoors with
glass windows
4.524 4.774 2.600
Outdoors 6.434 6.931 4.114

[UV/BL (290nm~500nm) Strength of light in all spectrums]

BL (mW/cm2) 9h 14h 17h
Indoors with
glass windows
3.476 3.484 2.195
Outdoors 3.476 3.484 2.420
BL Glass Window
Penetration (%)
100.0 100.0 90.7

[BL Glass Window Penetration]

The table above shows the results of observing the amount of blue light outdoors and indoors through a glass window at different times of the day. The window penetration of blue light shows a surprising result! The strength of blue light measured indoors through a glass window is identical with that of outdoors, suggesting that 100% of the blue light in the sunlight reaches indoor spaces as well. While only 6% of UVB and 36% of UVA reach the earth’s surface, blue light makes a 100% touch down.

One can never be safe from blue light whether indoors or outdoors! According to LBLL, being exposed to blue light for over 1.5 months makes the skin dull and dry. After 4 months of exposure to strong blue light, the skin loses its elasticity, becomes red and the dryness becomes aggravated.

One of the more interesting findings was that the level of skin damage from the combination of UV rays and blue light was much greater than that induced by blue light alone.

Melanin Index graph / Elasticity graph

The chart above shows that skin damage, such as melanin increase and reduced elasticity, was more affected by the combination of UV rays and blue light compared to the sole influence of UV rays. Skin redness was more associated with UV rays than blue light, but the level of damage was higher with the combination of the two lights.

There exist UV rays and blue light both indoors and outdoors, and they accelerate skin aging. They just have different strengths! That also reminded me of myself though being completely unaware of that knowledge, sitting in front of my laptop with my unprotected face and writing things, and drinking coffee by the window and looking into my cellphone. Then at night, I devoted my heart and soul to skin care using cosmetics in the attempt to have clear skin. To avoid pouring water into a sieve like I did, it’s a smart idea to make a habit of blocking UV rays and blue light both indoors and outdoors, by using a product that is able to protect you against blue light.

Other Research