Blue light and health

Humans depend on the sun as the primary source of light for activities throughout history and lived mostly in darkness after sunset with limited lighting capability. Life is transformed with Thomas Edison’s invention of electricity and the first light bulb. Today, we live in a world that is illuminated with artificial lighting of various colours, always. There is an increasing concern of the potential health and environmental impacts of light pollution these days [1].

The visible light spectrum.

Light is the electromagnetic spectrum of wavelengths that is visible to humans. Our eyes can only detect a very narrow range of wavelengths ranging from about 400 to 700 nanometres [2]. This range of visible wavelengths is detected as colours in human vision from violet to red, the rainbow colours. White light is a combination of all these visible colours. Light of different colours can affect human physiology and health differently, as discovered by science in recent years [3]. Specifically, overexposure to blue light can affect one’s health in several ways.

Three generations of light bulbs – LED, fluorescent and incandescent.

Overexposure to blue light

In the past decades, we have seen significant changes in lighting technology. The old filament or incandescent light bulbs were first replaced with fluorescent lamps and subsequently with high brightness light-emitting diode (LED) lights. LED lights technology has many advantages; they are more power-efficient, low in radiating heat, reliable, and can last longer. No doubt, LED lights are more environmentally friendly. As such, the world is rapidly switching to LED lights. Although the white light generated from these lighting technologies may look similar to human eyes, spectra analysis has shown that their light spectrum emissions are quite different. Incandescent bulbs emit red light predominantly, fluorescent lamps show more green, and LEDs radiate mostly blue [4].

Like it or not, blue light is all around us!

Besides general lighting, LEDs are also widely used in display devices, including televisions, computer terminals, laptops, tablets, and smartphones. LED-backlit (backlight) display is now the dominant technology powering electronic reading devices [4]. Human no longer depends on the reflection of lights on paper for reading. Instead, direct light is used. Hence, we are regularly bathed in blue light and have blue light directly shined into the retina – a reality of modern living.

Circadian rhythm

Circadian rhythm is our inner biological clock that governs the sleep-wake cycle. The disruption of the circadian rhythm can affect one’s physical and mental well-being as I have discussed in another post (See “Follow your body’s daily cycle for good health”). Research has found that blue light’s short wavelengths are the most potent agent that affects and synchronise with the circadian rhythm. As the human body evolved based on the earth’s natural light-dark cycle, one will become alert in the daylight under the blue sky. Hence, numerous studies have shown that exposure to blue light improves cognitive performance, memory, vigilance, and mood [5–7].

Overexposure to to blue light from computer screen can be a cause of insomnia.

The downside, though, is one become too alert at night and cannot get into sleep. Melatonin, the sleep hormone, is particularly sensitive to blue light and can be most effectively suppressed with blue light in the range of 446 and 477 nm [8]. A study has shown that blocking blue light with amber lenses can significantly reduce insomnia symptoms and improve overall sleep quality [10].  Chronic exposure to blue night, especially at night will disrupt the circadian rhythm leading to a wide variety of adverse health consequences, including increased risk for premature death, cancer, metabolic syndrome, cardiovascular dysfunction, immune dysregulation, reproductive problems, mood disorders, and learning deficits [9].

Eye damage

Constant exposure to high energy short wave blue light between 415 and 455 nm can be very harmful to the eye. Blue light can penetrate the cornea, the front end of the eyeball, to cause increased oxidative stress and affect the cell structures with the cornea [11].

Blue light can also affect the lens, which functions as a filter to reduce retinal by short light waves. The lens contains structural proteins and enzymes which can absorb blue light. With increasing blue light, the lens’s proteins produce yellow pigments, which gradually darken the lens to block out more blue light. These protective effects of the lens decrease its transparency and lead to cataract formation [11].

Blue light can damage the eyes, causing dry eyes, cataract, and age-related macular degeneration.

The blue light that escapes the lens can damage the retina, causing degeneration, inflammation, and injuries to cells. Therefore, overexposure to blue light is responsible for increasing the occurrences of dry eye, cataract, and age-related macular degeneration [11].

Protect yourself from blue light

Blue light can be a double-edged sword. So, learn to take full advantage of it during the day and protect yourself from its harmful effects at night. Here are some tips:  

  • Get good sunlight exposure during the day, especially in the morning to mid-day, and this will improve your performance and mood during the day and improve your sleep at night.
  • Avoid reading or looking at bright screen two to three hours before bedtime.
  • Use a blue light filter for reading from electronic devices.
  • Eat foods high in β-Carotene, Lutein, and Zeaxanthin, such as Goji berries, provide antioxidant for eye protection from oxidative stress.
  • Doing blinking exercise to prevent dry eye.   
Reading your iPad before going to sleep is not a good bedtime habit!


Eat more vegetables. They are good sources of antioxidant for eyes.

While necessary for human cognition and performance during the day, blue light can become harmful at night. Overexposure to blue light is a cause for increasing cataract and age-related macular degeneration in recent years, not to mention the negative consequences of circadian rhythm disruption. Learn to protect yourself from blue light with blue light filter, antioxidant nutrients, and good bedtime habits.  


[1]         L. Tähkämö, T. Partonen, A.-K. Pesonen, Systematic review of light exposure impact on human circadian rhythm., Chronobiol. Int. 36 (2019) 151–170. doi:10.1080/07420528.2018.1527773.

[2]         D.H. Sliney, What is light? The visible spectrum and beyond, Eye (Lond). 30 (2016) 222–229. doi:10.1038/eye.2015.252.

[3]         A.J. Metz, S.D. Klein, F. Scholkmann, U. Wolf, Continuous coloured light altered human brain haemodynamics and oxygenation assessed by systemic physiology augmented functional near-infrared spectroscopy., Sci. Rep. 7 (2017) 10027. doi:10.1038/s41598-017-09970-z.

[4]         G. Tosini, I. Ferguson, K. Tsubota, Effects of blue light on the circadian system and eye physiology, Mol. Vis. 22 (2016) 61–72.

[5]         V. Gabel, M. Maire, C.F. Reichert, S.L. Chellappa, C. Schmidt, V. Hommes, A.U. Viola, C. Cajochen, Effects of artificial dawn and morning blue light on daytime cognitive performance,  well-being, cortisol and melatonin levels., Chronobiol. Int. 30 (2013) 988–997. doi:10.3109/07420528.2013.793196.

[6]         C.M. Beaven, J. Ekström, A comparison of blue light and caffeine effects on cognitive function and alertness in humans, PLoS One. 8 (2013) e76707–e76707. doi:10.1371/journal.pone.0076707.

[7]         A. Barba, F. Padilla, A. Luque-Casado, D. Sanabria, Á. Correa, The Role of Exercise-Induced Arousal and Exposure to Blue-Enriched Lighting on Vigilance, Front. Hum. Neurosci. 12 (2018) 499. doi:10.3389/fnhum.2018.00499.

[8]         S. Wahl, M. Engelhardt, P. Schaupp, C. Lappe, I. V Ivanov, The inner clock-Blue light sets the human rhythm, J. Biophotonics. 12 (2019) e201900102–e201900102. doi:10.1002/jbio.201900102.

[9]         J.A. Evans, A.J. Davidson, Chapter Ten – Health Consequences of Circadian Disruption in Humans and Animal Models, in: M.U.B.T.-P. in M.B. and T.S. Gillette (Ed.), Chronobiol. Biol. Timing Heal. Dis., Academic Press, 2013: pp. 283–323. doi:

[10]      A. Shechter, E.W. Kim, M.-P. St-Onge, A.J. Westwood, Blocking nocturnal blue light for insomnia: A randomized controlled trial., J. Psychiatr. Res. 96 (2018) 196–202. doi:10.1016/j.jpsychires.2017.10.015.

[11]      Z.-C. Zhao, Y. Zhou, G. Tan, J. Li, Research progress about the effect and prevention of blue light on eyes, Int. J. Ophthalmol. 11 (2018) 1999–2003. doi:10.18240/ijo.2018.12.20.