What Is Blue Light?

What is Blue Light? 

Blue light is one of the seven primary colours in the visible light spectrum. The 'rainbow' colours; red, orange, yellow, green, blue, indigo and violet each have their own wavelength and energy level. As can be seen from the illustration below, blue light sits somewhere in the middle of the visible light spectrum, meaning it has a short wavelength, between 400 and 500 nanometers (nm) and a relatively high energy level (2.5 - 3.0 eV). It is the combination of these two factors that makes exposure to blue light a cause for concern.

Not all blue light is bad. Natural blue light from the sun is delivered as part of the full light spectrum, balanced out by the other primary colours, as well as infrared and UV wavelengths. In contrast, artificial blue light is delivered without the full spectrum of light, leading to adverse effects for human health. Our exposure to artificial blue light from sources such as smartphone screens, television, laptops, LED lighting etc, has increased exponentially and it has experts concerned about the damage that blue light could be doing not only to our eyes, but also to our sleep and skin. 

How is Blue Light Bad for our Eyes? 

Studies have shown that the lower wavelength combined with the higher energy level of blue light allows it to quickly travel past the lens and cornea of the eye, directly to the retina. Over exposure of blue light to the retina can cause photo oxidation: a release of free radicals in the retina of the eye. Other studies have shown that over exposure to blue light can cause inflammation of the cornea and, in certain cases, can heighten the risk of developing age-related macular degeneration. 

Most people who work or study on screens for extended periods of time each day will have suffered dry eyes, blurry vision or itchy, irritated eyes. This is often referred to as Computer Vision Syndrome or Digital Eye Strain associated with too much exposure to blue light on the eyes. 

Does Blue Light Affect Sleep? 

It sure can, particularly if we're exposed to too much blue light in the evening, before bedtime. During the day, our body's natural circadian clock relies on natural blue light, as part of the full light spectrum. Blue light during the day tells our brain that the sun is up and that we should be awake. When the sun goes down however, and with it the natural daytime blue light, this tells our brain that it is now night-time and our body gets ready for a restful sleep. It does this by releasing the 'sleep hormone' melatonin.

However, using phones, laptops, televisions, LED or fluorescent lighting in the evening exposes receptors in our eyes and skin - known as melanopsin receptors -  to the same blue light that we rely on during the day to keep us awake. As our eyes and skin receive the blue light into the late evening, it is telling our brain that there is no need to produce melatonin  and we stay awake. When we do eventually turn off the screen and head to bed, we haven't produced enough melatonin to help us drift off to sleep quickly which reduces the amount of quality sleep we get throughout the night. 

Blue Light Effects on Skin

It is well known that UV light from the sun can damage our skin cells. More recent studies however, have shown that blue light, given its short wavelength and high energy characteristics, could also be harmful to our skin. While further research in all areas of blue light is warranted, studies have shown a link between exposure to blue light and the formation of free radicals and reactive oxygen species on human skin. 

A 2018 study revealed that artificial blue light can also decrease the amount of molecules in the skin known as aquaporins, which control the passage of water through the skin. Fewer aquaporin molecules means that less water is passed through the skin, significantly damaging the skin's hydration, potentially leading to premature ageing of the skin. 

Given that our skin in the largest organ of the human body, it is necessary to limit our exposure to artificial blue light as much to our skin, as to our eyes. 

How to Reduce Blue Light Exposure

When we consider an average day in our lives, it is alarming to discover how frequently, and for how long, we are exposed to artificial blue light.

If we wake before sunrise, we switch on our LED or fluorescent light or lamp. We might check our smart phone for emails or text messages or sit and scroll through the news while having breakfast. For many of us, our day is spent working or studying in front of a computer or laptop screen. In an office setting this is often taking place under LED or fluorescent lighting. Our daily commute might involve a backlit eBook reader or flicking through our smart phone. When we return home at night, it's not long before the overhead lighting is switched on and we relax in front of the television until bedtime. 

Becoming aware of our blue light exposure, especially at night as we prepare for sleep, is an important first step. We can look at small habit changes to quickly and effectively reduce the amount of time our eyes and skin are exposed to artificial blue light, including:

  • Limiting our scrolling and viewing time on devices and television and picking up a newspaper, magazine or book instead
  • Getting enough natural, full spectrum lighting during the day - particularly first thing in the morning - to help regulate our circadian rhythm
  • Practising the 20/20/20 rule to give your eyes a break from the blue light: if using a device that emits blue light, stop every 20 minutes to focus on objects that are around 20 feet (6 metres) away. Study those objects for 20 seconds before you return to your up-close viewing
  • Removing all sources of blue light from your bedroom; including devices and backlit LED alarm clocks. Using a blue light-blocking eye mask for sleep can also help to protect your sleep
  • Using a blue light filter app on our devices which set the screen at warmer orange and red tones to reduce the amount of blue light
  • Swapping out blue light-emitting LED and fluorescent lighting for blue light-free bulbs and lamps in our home 
  • Eliminating blue light from devices or modern lighting in the couple of hours before bedtime to improve our sleep habits; playing a game, reading a book or choosing a quiet activity by candlelight or firelight is a healthier option to end the day and prepare our bodies for restful sleep
  • Protecting our eyes from blue light when using devices with a pair of blue light filtering glasses
  • Safeguarding our skin from blue light while we work and play on computers and devices with a blue light filtering screen protector 

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