Wellness

What Is Blue Light? A Complete Scientific Guide

Moira Lawler
By
Justin Laube, MD
by

Screens have become crucial to our work lives and our social lives, too.

According to data from 2018, the average American spends more than 11 hours each day interacting with digital media.

And more screen time means there’s been a significant increase in blue light exposure.

Blue Light Definition

What is blue light? “All the light we see is made up of different wavelengths of light,” says Vivienne Sinh Hau, MD, an ophthalmologist at Kaiser Permanente in Riverside, California. “Certain wavelengths show certain colors.”

Blue light has the shortest wavelength and the highest energy. It vibrates between 380 and 500 nanometers.

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Sources of Blue Light

Blue light from screens is usually what people are referring to when talking about blue light exposure. But screens aren’t the only source.

“We see blue light in everything we do — it’s practically in everything,” Dr. Hau says. About one-third of all visible light is blue light.

 The most natural source is sunlight, but LED TVs, fluorescent lights, smartphones, tablets, and computers emit blue light, too.

Other Types of Light on the UV Spectrum

Red, orange, yellow, green, blue, indigo, and violet make up the visible spectrum of light.

 Each one has a unique energy and wavelength, with longer wavelengths for red and shorter wavelengths for blue.
Lights that have longer wavelengths than those in the visible spectrum are called infrared light, and those with shorter wavelengths are called ultraviolet (UV) light.

The UV spectrum is broken down into three groups:

  • UV-A This light — sometimes called “black light” — has the longest wavelength and causes the least amount of harm to the eyes.
  • UV-B This is the light that can commonly lead to sunburn.
  • UV-C This is the most damaging type of light and is used as a disinfectant in food, air, and water.

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Blue Light Benefits

In most cases, you hear about blue light in a negative context. But blue light has some positive aspects, too. Just think about how opening the blinds in the morning and letting sunlight come in helps you feel energized and awake.

Blue light may also help:

  • Promote alertness
  • Boost memory and cognitive function
  • Elevate mood
  • Regulate circadian rhythm to enhance healthy sleep (though only when exposure occurs during daytime hours and not too close to bedtime — more on that later)
When used therapeutically, blue light may also help with certain skin issues, such as acne, sun damage, and nonmelanoma skin cancers.

RELATED: How to Help Reduce Your Risk for Skin Cancer

Potential Dangers of Blue Light

On the other hand, too much blue light exposure can lead to:

  • Sleep Disruption Exposure to blue light can mess with your circadian rhythm, which can negatively affect sleep. According to a 2019 systematic review, taking in blue light for two hours at night suppresses production of melatonin, which is the hormone that makes you feel drowsy and helps you go to sleep.

     Blue light essentially tricks your body into thinking it’s daytime, which makes sleep harder to come by.

  • Eye Strain You may experience digital eye strain from looking at screens for too long due to the fact that blue light scatters more easily than other lights, which can reduce contrast.

     It’s not only blue light that’s the issue. The way we use screens also contributes to eye strain. “When we’re on these devices, we become zombies,” says Tamiesha Frempong, MD, an ophthalmologist with Mount Sinai Hospital in New York City. “We don’t blink as much as we do in normal conversation, and so the eyes dry out.” Nearly 6 out of 10 American adults report experiencing digital eye strain symptoms, such as headaches and dry eyes.

     This discomfort is often temporary and usually subsides after you step away from the screen.

You may also be curious about whether exposure to blue light harms your skin. A review published in 2023 found numerous studies showing how blue light can accelerate aging of the skin and darkening spots, although the mechanisms are not well understood yet.

While eye strain and sleeplessness aren’t ideal, blue light from your devices likely isn’t going to permanently harm your eyes or lead to macular degeneration.

 “There’s no evidence that blue light causes damage to the eyes,” Dr. Frempong says.

None of the experts we talked to are concerned about blue light. But they are concerned about screen time.

“We do need to be worried about being glued to these devices all the time — and kids in particular because of childhood obesity and the need for socialization,” Frempong says. A review published in 2018 found excessive screen time among children and adolescents can also lead to poor sleep, increased risk for cardiovascular issues like high blood pressure, and changes to emotional regulation.

Everyone responds to screen exposure differently, so it’s difficult to say how much is too much. The National Heart, Lung, and Blood Institute recommends you limit your screen time outside of work to two hours per day.

RELATED: Is Blue Light Harming Your Skin Health?

Tips for Reducing Exposure to Blue Light

You can try setting your devices to night mode to try to keep the blue light from interfering with your sleep. Apple’s Night Shift setting automatically adjusts the screen display to a warmer temperature when the sun sets in your location. The warmer hues are meant to be less irritating on the eyes.

This setting is also available for Android devices, as well as many laptops.

It sounds nice in theory, but don’t give it too much weight. According to a study published in 2021, enabling the feature didn’t lead to better sleep for the study participants.

 Those who stayed off their phones completely had higher-quality sleep than those who set their phones to Night Shift. So if you’re having trouble falling asleep, it’s better to ditch the device entirely.

You can also take steps to reduce eye strain if you must be on your electronic devices regularly. These steps can include:

  • Abide by the 20-20-20 rule. After 20 minutes of screen time, look at something that’s about 20 feet away for 20 seconds. “Just basically look out a window,” Frempong says. “These breaks allow your eyes to go back to their resting position.”
  • Sit an arm’s length (about 25 inches) away from the computer screen, and position the screen so you’re looking slightly downward.
  • Adjust the contrast on your screen or the lighting in the room. More contrast will reduce eye strain.
  • Treat dry eye symptoms with artificial tears. If you’re using drops more than four times a day, make sure you’re using the preservative-free kind, Frempong says. Preservatives in the drops can cause irritation.

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Do Blue-Light-Blocking Glasses Work?

Because of the increased screen time in recent years, glasses with a special filter designed to block blue light have become increasingly popular. These glasses are intended to protect the eyes from too much blue light exposure.

You may try them and find they reduce the symptoms of digital eye strain, but research so far has not found them to have a significant effect. A systematic review published in 2017 found a lack of evidence that blue-blocking lenses improve sleep, reduce eye fatigue, or protect eye health.

 The American Academy of Ophthalmology also doesn’t recommend them because there isn’t sufficient evidence that blue light damages the eyes to begin with.

If your eyes are bugging you because of exposure to too many electronics, your best bet is to refer to the aforementioned tips. “Those things I think have a bigger impact than the blue-light-filtering glasses,” Frempong says.

RELATED: 9 DIY Ways to Manage Dry Eye

Summary of What to Know About Blue Light

Screen time is a concern for many right now. And while that comes with increased blue light exposure, you’ve been exposed to blue light all along.

“Blue light is everywhere — it’s not just from the computer screens,” Frempong says.

Blue light is often pitted as dangerous, but it’s not believed to cause any long-term issues. Digital eye strain is real, however. Taking frequent breaks, adjusting the contrast on your screens, keeping devices about 2 feet away from your eyes, and using artificial tears if dry eyes are bothering you can help provide relief.

Editorial Sources and Fact-Checking

Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.

Sources

  1. Time Flies: U.S. Adults Now Spend Nearly Half a Day Interacting With Media. Nielsen.
  2. How Blue Light Affects Your Eyes, Sleep, and Health. UC Davis Health.
  3. Ultraviolet (UV) Radiation. UCAR Center for Science Education.
  4. Visible Light. UCAR Center for Science Education.
  5. Blue Light and Your Eyes. Prevent Blindness.
  6. Blue Light Therapy for the Skin: What Can It Do? Cleveland Clinic.
  7. Systematic Review of Light Exposure Impact on Human Circadian Rhythm. Chronobiology International.
  8. How Blue Light Affects Sleep. Sleep Foundation.
  9. The Vision Council Shines Light on Protecting Sight — and Health — in a Multi-Screen Era. The Vision Council.
  10. Are Blue Light-Blocking Glasses Worth It? American Academy of Ophthalmology.
  11. The Impact of Blue Light and Digital Screens on the Skin. Journal of Cosmetic Dermatology.
  12. Will Blue Light From Electronic Devices Increase My Risk of Macular Degeneration and Blindness? Harvard Health Publishing.
  13. Adverse Physiological and Psychological Effects of Screen Time on Children and Adolescents: Literature Review and Case Study. Environmental Research.
  14. Reduce Screen Time. National Heart, Lung, and Blood Institute.
  15. Does iPhone Night Shift Mitigate Negative Effects of Smartphone Use on Sleep Outcomes in Emerging Adults? Sleep Health.
  16. Protect Your Eyes From Harmful Light. Mayo Clinic Health System.
  17. The Effect of Blue-Light Blocking Spectacle Lenses on Visual Performance, Macular Health and the Sleep-Wake Cycle: A Systematic Review of the Literature. Ophthalmic and Physiological Optics.

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