Blue light – bad or good stimulator?

Birds start singing in the early morning directly with the first rays of the light from the Sun. It is caused by the light that regulates the biological activity of the living organisms. The light changes the biological clock by suppressing the production of the natural hormone – melatonin. It happens due to its high sensitivity and its tendency to change, especially by short-wavelength light like blue and violet, which stimulates the brain the most effectively. Why? Because the light is an invaluable life stimulator, however, its influence does not always bring only benefits. In the age of rapid technology development, people are practically exposed to various types of light-emitting screens, even during their sleep hours. They are surrounded by incredible numbers of the blue light source all the time. A natural question arises if and how does blue light affect humans? Is excessive exposure to it truly harmless? Here, we will try to answer this question. First, we start from the way we perceive blue light and process it. Then, we briefly describe the ways to protect against its disastrous effects and the areas, where we can use its beneficial effects.

Image credit: Pixabay (Free Pixabay license)

Blue light and its sources

It is known that light stimulates living organisms. Visible light consists of electromagnetic waves that have different length, called the wavelength. Depending on the wavelength, they have various colors from violet to red, where the violet light has the shortest wavelength and the red one has the longest one. Such short-wavelength light stimulates our brain more effectively than long-wavelength light. Moreover, blue light may also raise the core body temperature and quicken Heart Rate. Overall, short-wavelength light decreases the feeling of sleepiness in the evenings, which is the reason why it is not recommended to stimulate brains with this type of light right before bedtime. We are more surrounded by blue light (between 380 and 525 nm), it can be found nearly everywhere in today’s world. Blue light is emitted by nearly all modern devices such as TVs, smartphones, tablets or computers – which are the largest source of blue light – and even in LED lighting. Of course, the blue is not only artificial creation but also a component of white light, the one that the sun radiates.

Biological effects of blue light 

It is known that blue light is not neutral towards the human body [1]. It affects organisms in various ways, especially eyes, brains and skin [2, 3].  In particular, blue-violet  (wavelengths between 380 and 440 nm) are seen as potentially damaging. While they emit high energy they are considered as one of the possible causes of photoretinitis (i.e. acute inflammation of conjunctivitis and corneal epithelium). The human lens is a transparent, flexible organ focusing the light rays so that they create an inverted and reduced image on the retina. It is designed to block short-wavelength light, but when it is exposed to high amounts of it, the lens starts producing protective pigments, which cause it to be more opaque and that may lead to cataracts, which limit the eyesight and are the main cause of blindness [4]. Human lenses are not able to stop blue light along with other light colors from entering deeper parts of the eye, although short wavelengths are absorbed by the tissue just behind the retina what leads to its degeneration. In Figure 1 it is shown how the blue light, UVA and UVB affect the human eye. Generally, blue light signals the brain to wake up, however, overexposure to blue light contributes to many eye and brain problems. It reduces the melatonin level inside humans’ brains that is a crucial hormone when it comes to sleep cycles. The excess of blue light may contribute to its complete imbalance, and may lead to insomnia. Moreover, as due to numerous sex-related differences in central nervous system dopamine function, the blue light stimulation leads to different response for males and females [5].

Figure 1. The influence of the blue light on the human eye, [M. Osial].

Surprisingly, blue light can be also helpful, especially during the day, in which blue light makes people more energized and ready to act. It plays an invaluable role in the regulation of the human biological rhythms and affects the general well-being. The right proportion of the blue light helps to ensure hormonal balance, which contributes to general feeling and helps avoid sleep disorders. So, the blue light can be successfully used in for seasonal mood disorders, in particular in winter, while entire society suffers the light lack.

Influence on mental health 

Too much blue light causes sleep problems, which may even lead to serious sleep disorders [6]. When we have a sleepless night or sleep too short, the next day may impair our memory and contribute to hard learning and working processes. If such a state lasts longer, it will lead to the formation of neurotoxins in the brain, which will effectively prevent good sleep and contribute to deteriorating mood and, in the future, even health. Except for the psychological issues, disrupting melatonin can affect other hormones, which is responsible for hunger control. As a result, the obesity risk is growing up. Blue light is also a good indicator of headaches and migraine.

The melanopsin, which is a photopigment belonging to the light-sensitive retinal proteins, is maximally sensitive to blue light [7]. It is responsible for circadian information covey signals induction [8]. It plays a crucial role in humans as well as other mammals’ cardiac rhythms, i.e. biological cycles that have about 24‐hour periods, which exhibit daily oscillations [9]. Interestingly, the blue light influence of humans seems to be similar to a cup of espresso [10].

How to deal with artificial blue light? – blocking methods

Due to the fact that excess of the blue light causes several health problems several methods to protect against it were created. The most basic and popular form of protection is the use of amber lenses in glasses or artificial amber lenses, which block blue light and protect eyes against it. Since blue light influences our brain by affecting the eye, simply blocking it from entering the pupil can make a huge difference. It has been proven that wearing glasses with amber lenses for three hours before going to bed vastly improves sleep quality. However, it is important to remember that blue light is most harmful in the evenings and at night and we should not block it in the morning when it makes us energetic.

A different solution to reduce the blue light in our daily lives would be to either use screen-filters for blue light in every electronic device used before bedtime or install apps that decrease the amount of it in the evenings by themselves [11]. Otherwise, the supplementation of the lutein that is a natural protein in plants and zeaxanthin naturally occurring in some vegetables has a good influence on eye conditions and improves human visual performance [12].

Blue light benefits

The blue light can be very dangerous and induce many illnesses, especially in the brain and eyes area. Surprisingly, short wavelengths can also be very beneficial and even have healing properties. For example, in skin treatments [13]. It may be used to destroy acne-inducing bacteria, which has a huge impact on people suffering from skin problems. It is all because of blue light’s wavelength – it has different properties than longer or shorter wavelength light. In acne treatment, blue light has the best length to be absorbed by porphyrins, crucial organic compounds produced by acne-inducing bacteria [14]. This causes the release of reactive oxygen species that can affect bacteria. That is also a reason why sunlight has antibacterial properties. After all, it is a mixture of different lights, including the blue one.

The skin contains three main layers like epidermis – the outermost layer of the skin containing various internal layers, dermis – fibrous network of tissue that provides structure to the skin, and hypodermis that is the deepest layer of the skin containing fat tissues that insulate the body from cold temperatures. Due to the properties of short wavelengths, that light can get through deeper layers of human skin into the hypodermis, see Figure 2. In some instances, this could mean skin’s premature ageing, in others as a treatment for particular skin diseases, like keloids. Keloids are a result of fibroblasts’ very intense dividing, so blue light, being able to reach them in deeper levels of the skin, can decrease the frequency of their divisions and migration speed, being a possible remedy for this and other fibrotic skin diseases. Blue light can also stimulate keratin production [15]. For now, light therapy is used for stimulation of some proteins production like collagen and elastin, while maybe in the future, short-wavelength light could be an inexpensive and effective treatment for human wounds.

Figure 2. Light type penetration of the skin, [M. Osial].


It is known that light stimulates life. Humans can see only a thin spectrum of light, ranging from red to violet. Blue light makes the highest influence on our body and changes our habits. Smartphones, tablets and other digital displays make people spend far more time looking at things at the close range, much more than the human body was adapted to it in the process of evolution. Additionally, there are fewer and fewer darkened places on the ground during the night. Ubiquitous light contributes to background brightness that is too low. A lot of people suffer shortsightedness, and still more suffer from increasingly serious eye conditions, including even blindness. It also leads to eye fatigue and pain, both indicators of computer vision syndrome. Its harmful influence should not be ignored and appropriate protective methods should be applied, however blue light also has a bright side, and we one should not forget about its positive overtone like light therapy.

This article is a joint work of Zuzanna Kozłowska (Faculty of Chemistry, University of Warsaw), Agnieszka Pregowska (Institute of Fundamental Technological Research, Polish Academy of Sciences) and Magdalena Osial (chyba Faculty of Chemistry, University of Warsaw)


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