Blue Light: Effects on Sleep & Health

By Charlie Huntington, M.A., Ph. D. Candidate
Reviewed by Tchiki Davis, M.A., Ph.D.

Blue light can damage our skin and eyes and interrupt our natural circadian rhythms. This article describes how this happens and how you can protect yourself from the effects of blue light.

*This page may include affiliate links; that means we earn from qualifying purchases of products.

Perhaps you are familiar with the idea of being in a flow state, that state of mind where you lose track of time as you get utterly engrossed in an activity, often finding great satisfaction in it (Csikszentmihalyi, 1991). For me, flow states can happen while running, playing guitar, and when working on writing projects. When I’m at the computer, I can become so focused on what I’m writing that I hardly move my eyes from the screen.

When I snap out of that focus, I suddenly notice that my eyes are tired and sore. I can blame dry eyes from staring for some of the discomfort, but not all of it. Another reason that those writing marathons can hurt my eyes is because of the blue light emitted by my computer screen. In fact, I recently added software to my computer that stops it from generating blue light, and now my writing sessions go by with less discomfort.

If you’re not aware of the effects blue light may be having on your well-being, you’ve come to the right place. Let’s dive into the science on blue light. We will see how it mostly hurts us, but might be able to help in a few key ways, and we will learn about the steps you can take to reduce its impact on your own health.

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What Is Blue Light? (A Definition)

Blue light is light of a certain wavelength that can be emitted or reflected by a variety of materials and surfaces in the world (Okuno et al., 2002). By its nature, blue light is damaging to the photoreceptors in the human retina. Some sources of blue light, such as the sun, certain metallic surfaces, and the sparks produced by metallurgy, give off so much blue light that it is highly damaging to look at them for more than a second or two (Okuno et al., 2002). Other sources, such as computer screens and fluorescent lights, emit lower concentrations of blue light, but still have the potential to harm our eyes.

Blue Light Effects

Blue light is best understood as having two main effects on humans, both of which I will explain in detail. First, it causes damaging chemical reactions in the different parts of the body it touches – not just our eyes, but our skin as well. Second, it sends powerful signals to our bodies regarding how awake we should be, and these signals can both help and harm us.

When blue light reaches our skin, it causes DNA damage by interacting with the oxygen and nitrogen in our skin (Suitthimeathegorn et al., 2022) as well as by generating an inflammatory response in the skin. Our bodies react to the blue light by producing more melatonin, which can cause what is called hyperpigmentation, or the darkening of the skin, to occur. In this sense, blue light is a part of the reason that most of us wear sunscreen on a sunny day – we do not want the direct sunlight (which includes blue light) to damage our skin. Over time, our unprotected skin can develop age spots, which are one manifestation of hyperpigmentation. (Regrettably, I can see a couple on my forearm right now as I’m typing.)

As an important side note on this topic, high concentrations of blue light, delivered in clinical or medical settings, have been used to treat skin that is already experiencing some kind of abnormality, such as acne or psoriasis (Garza et al., 2018; Scott et al., 2019). It appears that for skin that is already inflamed or damaged, blue light exposure may be beneficial, while for healthy skin, it is generally harmful (Garza et al., 2018). At this time, some home treatments using blue light to treat acne are available, but it is not recommended that one undertake this kind of treatment without the guidance of a medical professional (Gold et al., 2011).

The melatonin reaction from blue light impacts not only our skin, but our state of mind as well. This bodily response in turn impacts our circadian rhythms (Suitthimeathegorn et al., 2022) – the natural ebb and flow of energy in our bodies throughout the day, wherein we are more alert during the morning, then start to feel drowsy and naturally want to sleep in the evening. While exposure to blue light from sunlight is natural and can help us wake up, exposure to blue light when we want to be sleepy, such as late at night, can interrupt our bodies’ regulation of our wakefulness.

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Blue Light and Sleep

In other words, exposure to blue light can and does mess with our sleep. Especially in modern society, where we struggle as a culture to put down our smartphones, tablets, and laptops, all of this blue light exposure is disturbing our natural circadian rhythms (Burgess & Molina, 2014). Just when we want to be feeling drowsy and tired, exposure to blue light makes us feel more alert, raises our body temperature, and raises our heart rate (Cajochen et al., 2005).

All of that makes it harder to fall asleep when you’ve just finished your fifth episode of a sitcom and are suddenly lying in a pitch-black bedroom. Unfortunately, once people who’ve been exposed to blue light do actually get to sleep, things continue to be worse. Although people who’ve been exposed to blue light don’t sleep significantly less than people who haven’t been exposed to it, at least one study shows that they experience a lower ratio of deep to light sleep (Ishizawa et al., 2021). In other words, their sleep is less restful and regenerative.

As you might expect, this poorer sleep quality in turn affects a person’s functioning the next day. One research study observed that compared to controls who had a regular evening and night’s sleep, people exposed to blue light the night before were more lethargic and less alert the next morning (Kayaba et al., 2014).

Blue Light & Headaches

Being exposed to blue light for too long can not only make us overly alert and worsen our sleep, but it can also cause headaches and eye strain in the moment (Terman & Terman, 2005; Tosini et al., 2016). Headaches are the most commonly reported negative side effect of blue light therapies (Do et al., 2022), which are discussed below.

Blue Light Glasses

So how do we avoid the negative effects of blue light? Thankfully, blue light-blocking glasses are both the subject of scientific study and are readily available from eyeglasses manufacturers everywhere. A recent review of studies showed that for all people, but especially those with sleep issues or related disorders, blue light-blocking glasses can reduce the negative impacts of exposure to blue light (Shechter et al., 2020). Beyond improvements in sleep, there is some evidence that wearing blue light-blocking glasses at work may also increase people’s work engagement and positive behaviors at work (Guarana et al., 2021).

Blue light-blocking glasses do seem to be particularly helpful for people with sleep issues. For example, in one study, conducted with people whose sleep schedules had become highly delayed (in other words, they were night owls who didn’t want to be night owls), wearing blue light-blocking glasses increased their melatonin levels in the early evening and helped them go to bed much earlier in the evening (Esaki et al., 2016).

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Blue Light Blocking

Scientists have determined several other ways to reduce blue light exposure (Campiche et al., 2020; Ouyang et al., 2020). One can dial down the blue light exposure on the screens they use, typically by installing software for the purpose, although some devices may come with this functionality. (Based on the experiment I’m running on myself, this can be very effective!) Topical creams and antioxidants, such as sunscreens, clearly protect the skin from blue light damage. On the more invasive side of things, scientists have found that surgeries on the retina itself, such as implanting a lens that filters blue light, can also be protective. (I would suggest you start with adapting your devices and getting glasses, though!)

Blue Light Therapy

Now that I have told you so much about how damaging blue light is for our bodies and our sleep, will you believe me when I tell you that intentional blue light exposure can actually be beneficial? When it is judiciously applied, exposure to blue light can help in treating mental health and sleep disorders.

Blue Light Therapy for Seasonal Affective Disorder
First up, we have treatment for seasonal affective disorder (SAD), or the phenomenon of getting depressed during the winter, when days are short and exposure to sunlight is reduced. Multiple studies now attest to morning exposure to blue light being an effective treatment for symptoms of SAD, as well as regular old “non-seasonal” depression (Maruani & Geoffroy, 2019). Thankfully, this treatment can take as little as one week to start having effects.

This pattern also holds for people who experience some of the symptoms of depression, but not all (Meesters et al., 2016). I take this to mean that if you think you might not be getting enough sunlight, and that it might be impacting your mood at all, it probably couldn’t hurt to try out a lamp designed for just this purpose.

Blue Light Therapy for Traumatic Brain Injury
There is also evidence that blue light therapy can be beneficial for people who have experienced traumatic brain injuries; (Raikes et al., 2021). For example, morning exposure to therapeutic blue light reduces daytime sleepiness and improves the ability to concentrate in people recovering from a concussion (Raikes et al., 2021). Similar findings are emerging for a related population: people with diagnoses of posttraumatic stress disorder (Killgore, 2020).

Blue Light Therapy for Sleep
There is also a use for blue light that nicely complements the research I mentioned earlier about blocking blue light to help people fall asleep earlier. Another way to induce earlier sleep onset in the evening is to increase one’s exposure to blue light in the mornings (Geerdink et al., 2016). It would seem that increasing your exposure to morning blue light can encourage your circadian rhythm to start earlier in the day, leading to increased drowsiness earlier in the evening.

Blue Light Therapy for Performance
Remember how blue light exposure increases our levels of alertness? It appears that intentional exposure to blue light can help us be especially alert when the situation calls for it. A couple studies indicate that even a single exposure to blue light positively impacts our performance on cognitive tasks (Killgore et al., 2020; Tonetti & Natale, 2019).

Blue Light Therapy for Bacteria
And now, for a truly random use of blue light, some hospitals have tried using concentrated blue light to kill bacteria on various surfaces of their treatment and operating rooms, observing that it is effective in killing many of the fungi that cause infection in patients following surgeries (Trzaska et al., 2017).

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Final Thoughts on Blue Light

After writing this article, I started to notice just how often I’m around screens, and how bright they can be. I think this is just a fact of our daily lives – blue light isn’t going anywhere. Writing this article got me thinking about how to reduce exposure to blue light in my daily life, and I hope it does the same for you. So what can we do to promote healthy sleep and our skin?

For my part, I have started turning off the blue light on my Macbook, especially after sundown. I also turn down the brightness on my smartphone, and I try to make it a general priority to disengage from screens as much as possible after dinner. Consistent with the treatments I mentioned that utilize morning exposure to blue light, we might be better served by doing screen-based work early in the morning, because it will help us wake up, rather than at night, when screens can make it harder to fall asleep. And most importantly, I try never to use screens in bed, no matter how cozy it sounds to watch a movie from under the covers.

To learn more about blue light, I recommend the following video:

Video: Here's What Blue Light Actually Does To Your Body

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