Does blue Light disrupt the skin circadian clock

Improper exposure to blue light is becoming more of a concern as artificial sources of light become more common. LED lighting is growing in popularity as it creates greater lighting at a much lower energy cost. We perceive this as light that is more blue.

Exposing yourself to light at improper times of day disrupts your circadian rhythm. Specifically, exposure to blue light at night. Most of the focus on light centers around its effects on the eye. However, every system in your body has a circadian rhythm, so improper exposure can affect many tissues.

A new study published in the International Journal of Cosmetic Science shows that exposing the skin to blue light disrupts the local circadian rhythm. But are the results applicable to real life situations? Let’s find out.

Blue light at night

Effects of blue light on the skin

To test the effects on skin, researchers exposed skin cells called keratinocytes to blue light and tested levels of a circadian protein called Period 1(per1). Keratinocytes make up 90% of the surface of the skin.

Exposing keratinocytes decreased per1 levels, a marker of circadian disruption. And the disruption lasted for hours after the exposure, so it’s not a short term effect.

However, it’s important to point out that this was keratinocytes in a petri dish exposed to a very high level of light. This in no way represents real world conditions. But, that doesn’t mean that it’s not significant.

This seems like a good start to identify that light other than ultraviolet light does in fact have an effect on the skin. To represent a more realistic scenario, the researchers exposed keratinocytes to an Ipad/ tablet approximately 8 inches away for an hour. While this led to an 88% increase in free radical production, they didn’t measure per1 for some reason.

The second part of this study is a little more informative and realistic. It shows that blue light may cause skin damage and accelerate skin aging. The increase in free radicals in the Ipad portion of the study was approximately half the increase in the first part.

Is this significant, though?

Based on the function of the skin as a barrier, I don’t believe visible light plays a large role in regulating the circadian rhythm there. Exposing the skin to visible light does have physiological effects, though. Light therapy in the blue/green wavelength reverses the yellowing of the skin in jaundice. This happens by converting bilirubin in to water soluble metabolites that are can be removed from the skin and excreted in the urine.

So what do these study results look like in comparison to more important factors like UV exposure? An 88% increase of free radicals is certainly nothing to turn your nose at. But exposure of keratinocytes to ultraviolet A(UVA) radiation causes a nearly 4000% increase in free radical production.

Had they measured per1 levels in the tablet condition I’d have more confidence that real life blue light exposure causes significant circadian disruption. It’s also hard to determine the significance of these results when exposing keratinocytes to only blue light and no other zeitgebers.

If UV exposure is the dominant time cue, blue light may cause some level of disruption, but it’s tiny in comparison. I do believe that this study clearly illustrates that blue light exposure is damaging to the skin. So it may be a good idea to limit your exposure at night to allow the skin can heal.

To say it will cause circadian disruption is a bit premature. Blue light causes 1/50th the free radical production as UV light. Changes in free radical production likely play a major role in setting circadian rhythms. But I’m just not going to bet on 88% vs 4000% from a petri dish. I’d want an in vivo study under real life conditions to confirm.


Circadian rhythms help cells and tissues properly time repair away from damage. Free radical production is an important signal to help set the tone. In an ideal world, we expose our tissues to damaging stimuli during our active period and remove those exposures during rest. In humans, that happens during the day and night, respectively.

Many environmental factors can damage the skin, UV radiation being the most researched. This study clearly shows that blue light is damaging to the skin. This is concerning because our exposure to blue light from overhead lighting and handheld devices has dramatically increased.

In the grand scheme of things, blue light may have an impact on the circadian rhythms in the skin. I suspect it can induce circadian disruption. But without full exposure to visible and non-visible light throughout a 24 hour period, it’s hard to determine if these results are remotely relevant.

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