Blue Light: Where Does It Come From?

Medically Reviewed by Zilpah Sheikh, MD on February 12, 2024
Written by WebMD Editorial Contributor, Jodi Helmer
6 min read

Your tablet, smartphone, laptop, and flat screen TV all have one thing in common: They each give off blue light.

The colors in the visible light spectrum are:

  • Red
  • Orange
  • Yellow
  • Green
  • Blue
  • Indigo
  • Violet

You may know them by the acronym ROY G BIV. Together, they make the white light you see when the sun -- the main source of blue light -- is shining. Fluorescent and LED (light-emitting diode) light bulbs also give off blue light.

Visible light is a form of energy and part of the electromagnetic spectrum. Radio waves, microwaves, X-rays, and other kinds of light are also part of the electromagnetic spectrum, but visible light is the only part of it human eyes can see. 

Visible light wavelengths appear between 400 and 700 nanometers on the electromagnetic spectrum. In comparison, the wavelengths of radio waves are billions of times longer than visible light, while gamma rays are billions of times shorter.

Each color in the visible light spectrum has a different wavelength and energy level. Blue light has shorter wavelengths and higher energy than other colors. 

The approximate wavelength ranges (in nanometers) for visible light is:

  • Red: 650
  • Orange: 590
  • Yellow: 570
  • Green: 510
  • Blue: 475
  • Indigo: 445
  • Violet: 405

Blue light is located in a narrow band near an outer edge of the visible spectrum, with wavelengths close to those of ultraviolet light. Blue light triggers your eyes to react, especially the lens, retina, and cornea. Some research shows a link between eye damage and short-wave blue light with wavelengths between 415 and 455 nanometers. Most of the light from the LEDs used in smartphones, TVs, and tablets has wavelengths between 400 and 490 nanometers.

The sun is the greatest source of blue light. Natural blue light helps regulate your circadian rhythm, or wake-and-sleep cycle. Sunlight is also instrumental in children's eye development. There's some evidence that the lack of natural blue light might be a factor in a recent increase in cases of nearsightedness (myopia).

Growing evidence shows that blue light can:

  • Boost alertness
  • Improve attention span and reaction time
  • Help memory -- one study showed that 30 minutes of exposure to blue light led to better recall
  • Raise your mood and effectively treat depression 

Blue light is also used to treat skin conditions such as:

  • Acne, to get rid of the P. acnes bacteria that live on your skin and cause pimples
  • Precancerous actinic keratoses, the scaly, red spots caused by severe sun damage
  • Certain skin cancers, with photodynamic therapy, a light-activated drug treatment that targets cancer cells.

We expose our eyes to increasing amounts of artificial blue light through the use of electronic devices such as cell phones, laptops, tablets, and other digital devices. What does blue light do to your eyes?

Blue light is hard for our eyes to block, so nearly all of it travels to our retinas. There has been concern that continuous long-term exposure to blue light can damage retinal cells and cause eye conditions such as eye cancer, cataracts, and age-related macular degeneration.

Age-related macular degeneration (AMD) occurs when part of your retina, the macula, is damaged. AMD causes a loss of central vision. It's the primary cause of vision loss in people over 50.

Blue light is close to ultraviolet light in wavelength. Ultraviolet light is particularly damaging to tissue such as that in the retina, which is highly reactive to light, and some believe blue light may be damaging as well. Because of this, your retina can be prone to damaging oxidative stress. It depends on how much UV exposure your eyes get and for how long.

To date, researchers haven't found convincing evidence that daily exposure to artificial blue light causes long-term harm to your eyes, but most believe more study is needed.

However, blue light from digital devices can cause eye strain, with symptoms such as:

  • Dry eyes
  • Watery eyes and tearing
  • Blurred vision
  • Headache
  • Tired eyes
  • Irritation and soreness

To help reduce eye strain when using devices that emit blue light:

Rest your eyes regularly. Look away from screens every 20 minutes. Focus on a non-digital object 20 feet away for 20 seconds or more.

Sit or stand further away. Place monitors and laptops literally at arm's length, a distance of about 2 feet. Position your monitor at eye level or slightly lower.

Limit glare. Adjust screen contrast or brightness and lower nearby lights. Consider installing a matte filter on your device.

Keep your eyes lubricated. Use over-the-counter non-preservative eye-moistening drops frequently, even when your eyes are not bothering you. Avoid sitting under or above vents, as well as fans that blow directly into your eyes and face.

Visit your optometrist. Ask about glasses, lenses, coatings, and tints specifically for computer work and eye strain.  

 

 

 

Blue light helps regulate your circadian rhythm, the wake-and-sleep cycle. It keeps us awake and alert during the day. But watching TV or scrolling through social media too late at night can have the opposite effect. The blue light stimulates your brain, slowing or stopping release of the sleep hormone melatonin. That makes it harder to get a good night’s sleep.

You can’t avoid blue light completely, but there are ways to limit your exposure. Consider:

  • Limiting screen time. Avoid looking at your computer, phone, or tablet several hours before you plan to sleep. Set your devices to night or dark mode, which reduces brightness and glare, lowers levels of blue light, and prevents eye strain.
  • Using screen filters to lower blue light exposure. A screen filter on your computer, tablet, or phone will reduce blue light exposure but is only about half as effective as dark mode or dimming your screen's brightness. A matte filter also helps reduce glare and prevent eye strain.
  • Wearing blue light-blocking glasses, yellow-tinted computer glasses, or glasses with anti-reflective lenses. 

 

The higher energy and shorter wavelengths of blue light may damage your retina is the idea behind products such as blue light glasses. But there's no scientific evidence to support the theory that blue light is harmful to your eyes. Eye strain results from the way and length of time you stare at digital devices and is usually relieved by frequent breaks and other measures. The American Academy of Ophthalmology doesn't recommend the use of blue light glasses. 

Our biggest daily dose of blue light comes from the sun. The amount of blue light coming from your digital devices and home's LED television and lighting is significantly less. Because of the many ways we're exposed to blue light, research on its effects continues. 

What is blue light?

A tiny band on the visible light spectrum, blue light is a type of light we can see.

What color light helps you sleep?

Nighttime light generally interferes with sleep because it inhibits release of the hormone melatonin, which helps to regulate your wake-and-sleep cycle. But blue light appears to be more disruptive. Some early studies indicate that the longer wavelengths of red light and orange light may help promote sleep, but more research is needed.

Are blue light filters good for your eyes?

Blue light filters work, but they've been proven only half as effective as simple fixes such as decreasing the screen brightness on your devices or using dark (night) mode.

What are the pros and cons of blue light?

Blue light helps increase alertness and reaction times and improve memory. There is no evidence that blue light is harmful to your eyes, but the ways we use sources of blue light of can contribute to eye strain.