The impact of blue light and digital screens on the skin

The skin is frequently subjected to a variety of environmental trauma and stress. It is unavoidably subjected to blue light due to the increased use of electronic equipment, including indoor lighting and digital gadgets like smartphones and laptops, which have a range of detrimental effects. The method of action and numerous harmful consequences of blue light on the skin are the main subjects of this review.


| INTRODUC TI ON
Humans have been exposed to varying levels of visible and invisible light since the beginning of their development on earth. Moreover, the inescapable consequences of industrialization and global modernization have caused enormous changes in people's lifestyles in both developing and developed countries during the past few decades. Humans are now overexposed to artificial light during days and nights and do not receive adequate natural light during the day.
Artificial lights have been incorporated into daily life as a result of digitization, which has led to light pollution. To make the days longer for work or for modern life, artificial light has been produced. Therefore, our body no longer gets the cues it previously did to get ready for sleep and act according to normal circadian rhythm.
The change in the evening and night time light has also an adverse effect on our body circadian rhythm and general health. The skin, as the biggest organ in the body, is immediately exposed to both artificial and environmental light and the outside trauma. It serves as the initial line of protection against environmental hazards. The skin has also shown to have a substantial circadian rhythm due to its many activities. During the day, these functions are more protected, while at night or during darkness, they are more suited for repair. The effect of light on the skin has also therapeutic indications. Digital screens are among the latest methods of nonthermal light treatment that dermatologists may use. LEDs also emit a significant amount of blue light, with both positive and negative effects on the body and the skin. 1 Here, we are presenting a brief literature review on the various mechanisms by which, blue light damages skin as well as various preventative methods. The focus of this article is on the particular cell-signaling routes involved as well as how the processes at work might be used to treat a range of cutaneous issues.

| B LUE LI G HT: WHAT IS IT ?
Different wavelengths make up all the light that we see. Selected wavelengths exhibit some selected hues. The visible spectrum of light is made up of the colors including red, orange, yellow, green, blue, indigo, and violet. The electromagnetic spectrum's ultraviolet region is closest to blue light, which has the shortest wavelength.
These wavelengths have the highest energy and the shortest wavelength, while red light has the least energy and the longest wavelength. Depending on the source, the spectrum of this blue light typically ranges from 420 to 490 nm, with a peak emission between 440 and 460 nm. Infrared light and ultraviolet (UV) light are also two different types of light that have different wavelengths from those found in the visible spectrum.
At homes and inside the commercial buildings, LED lights are becoming more popular and taking the place of incandescent bulbs due to their high efficiency, compact size, and extended lifespan. 2 The main source of blue light is sunlight. There are also synthetic sources, though. Prior to the development of LED lighting, the main source of illumination was incandescent bulbs, which released light with wavelengths comparable to those that the sun naturally emits. Incandescent lighting sources were gradually phased out as the cost of LED lighting continued to drop. 3 Many businesses utilize LED lights in liquid crystal displays (LCDs) and lighting fixtures due to their tiny size, compact design, energy efficiency, and dependability. 2 It has a wide range of uses, including flashes in cameras, smartphones, current computer screens, televisions, smartwatches, and traffic signals. These LEDs also create a good amount of blue light, which is toxic and damaging to the eyes and skin. Concerns about the safety of these light sources have been raised by the fast-growing use of cellphones, tablets, laptops, and desktop computers, particularly during the COVID-19 lockdown, when people kept themselves occupied by browsing the Internet and watching televised programs. There is a growing concern about the long-term consequences, because of the proximity to the screen and the exposure time spent staring at the screen, even if the effects of blue light generated from electronic device screens are fewer than that of sun exposure. 4

| WHAT EFFEC TS DOE S THE B LUE LI G HT HAVE ON YOUR BODY ?
The circadian rhythm, or the body's natural sleep cycle, is regulated by blue light. The body's sleep cycle is regulated by exposure to the blue light during the day, which also encourages the generation of melatonin at night. The body's circadian rhythm is hampered by the increased use of gadgets like laptops and phones, even late into the night. The body's capacity to create melatonin is compromised by increasing the amount of blue light exposure before night, which results in difficulty falling asleep and drowsiness during the day. 5 Blue light improves mood, memory, and cognitive function while increasing alertness. According to studies, youngsters who aren't exposed to enough sunshine may experience problems with the eyes and visual development as well as growth. Research has also suggested that less exposure to blue light may be linked to an increase in myopia. 6,7 High-intensity blue light, a form of "visible light," penetrates the skin more deeply than UVB and UVA rays do. Moreover, emerging scientific evidence suggests that the blue light can permanently harm skin cells in the dermis and epidermis. This has the side consequence of damaging the DNA within these cells and stimulating the breakdown of the support fibers for the skin. This may cause fine lines, wrinkles, and premature aging over time. 8  Opsins, flavins, porphyrins, and nitrosated proteins are the primary and most significant photo acceptors (e.g., S-nitro-albumin). 9 The activation of flavins and flavoproteins is one such putative blue light pathway. When exposed to radiation, flavin mononucleotides (FMN) and flavin adenine dinucleotides (FAD) double the amount of superoxide that is produced when reactive oxygen species (ROS) are formed. ROS signaling is mediated in a variety of ways. One of these is an Nrf2-dependent process, which involves the production of antioxidant factors through the action of a "basic leucine zipper protein."

| B LUE LI G HT ' S MECHANIS M OF AC TI O N
Nrf2 has anti-inflammatory properties because it inhibits NF-kB, which controls the proinflammatory response. Flavin-containing proteins are present in many different types of cells. Cryptochromes are one of these proteins. 10 In a recent study, Buscone et al. hypothesized that blue light via cryptochrome 1 (CRY1), which is found in the hair follicle following exposure to 453 nm light, may have a beneficial influence on hair development. Ex vivo hair follicles showed a lengthening of the anagen phase, which may be related to the rise in CRY1 levels brought on by blue light exposure. 11,12 In the dermis, blue light also causes the release of free nitric oxide NO. At physiological pH, blue light at 420 or 453 nm caused a large amount of NO to develop from S-nitroso albumin as well as from aqueous nitrite solutions via a Cu(1+)-dependent process, as measured by chemiluminescence detection (CLD). Blue light irradiation considerably raised the intradermal levels of free NO, as discovered by electron paramagnetic resonance spectrometry in vitro with human skin specimens. Blue light irradiation of human skin resulted in significant NO emanation from the irradiated skin area as well as significant NO translocation from the skin surface into the underlying tissue, as detected by CLD in vivo in healthy volunteers.
NO reacts with superoxide to form peroxynitrite, which may cause DNA damage that results in cell damage but no apoptosis has been seen. Yoo et al. discovered that human keratinocyte and cutaneous fibroblast proliferation was inhibited by blue light. 13 According to some theories, the complex IV of the electron transport chain called cytochrome c oxidase, which is located in the mitochondrial membrane, maybe the mechanism through which blue

| HOW TO AVOID P OTENTIAL S K IN DAMAG E FROM THE B LUE LI G HT
The best treatment is prevention. It is more crucial to try to take preventative measures through various treatment. The simplest approach to minimize blue light damage is to restrict exposure and reduce screen time by taking frequent pauses from your device to rest your eyes. Attempt to take five-minute rests every 30 min. Invest in blue light screen filters or screen protectors for your electronic devices (such as a phone, tablet, or computer), which can block or tame blue light. Numerous businesses have created blue lightblocking eyewear that makes the same claims about improving sleep and reducing eye strain. The effectiveness of these lenses is still up for question among scientists, despite the fact that laboratory tests indicate that they should be beneficial. To decrease the emission of the blue light, switch your computer, smartphone, and other devices into "night mode". 1,25 The amount of blue light emitted by screen technology is influenced by several variables, including program code, the mobile operating system, and screen engineering (Calvo-Sanz & Tapia-Ayuga, 2020). 26  Physical and chemical sunscreens are the two primary categories of sunscreens. Physical sunscreens have active, physical components that are iron oxide, tungsten dioxide, zinc oxide and many more. Other ingredients include talc, red veterinary petrolatum, kaolin, calamine, and iron oxide. By reflecting, dispersing, or absorbing UV radiation, inorganic materials work. Their inherent drawbacks of being opaque and having a "whitening effect" can be lessened by using micronized or ultrafine particles. As soon as its applied, it rests on top of the skin. Physical sunscreens do provide blue light protection since the ingredients is made to reflect UV and blue light away from the skin. Chemical compounds that really absorb UV rays and may even hurt the skin are used to make chemical sunscreens. Blue light protection is not provided by chemical sunscreens. 30,31 Additionally, a number of substances-often referred to as "systemic sunscreens"-have a systemic photoprotective action like green tea polyphenols, PABA, antihistamines, aspirin, indomethacin, corticosteroids, beta-carotene, antimalarials, ascorbic acid, and tocopherols (i.e., vitamins A, C, and E) ( Table 1). 33 The skin makes use of a variety of antioxidative defense mechanisms, including the enzymes catalase and superoxide dismutase as well as natural products like L-ascorbate, beta-carotene, and glutathione, to control the production of ROS.
A diet high in antioxidants, including fruits and vegetables, is strongly advised in addition to topical application of antioxidantrich products. This is the healthiest and most long-lasting method of avoiding blue light harm to the skin.
Oral antioxidants, such as supplements of the vitamins C and E and glutathione, since all antioxidants work to scavenge free radicals.
The diet should include foods high in antioxidants like fresh fruits and vegetables like beans, spinach, beets, strawberries, blues, and raspberries, which can help the skin fight off free radicals. Plants produce red, orange, and yellow carotenoids, which have antioxidant characteristics. Carotene, lutein, zeaxanthin, and lycopene are a few typical carotenoids. Beta-carotene can be obtained in diet by eating dark green, red, yellow, and orange vegetables like spinach and carrots. The carrot root and extract, as well as a subtropical fruit extract, both contain carotene and are available as topical ingredients.
Another carotenoid called lutein, which makes up a large portion of the macular pigment, is renowned for its capacity to block blue light.
As was already noted, vitamins are also often used as ingredients in blue light protection products. Niacinamide, often known as vitamin B3, has been demonstrated to be helpful against hyperpigmentation brought on by aging. Niacinamide is a fantastic option to boost the protection of sunscreens in the visible spectrum. Vitamins C and E are well-known for their antioxidant properties, and research has shown that these two nutrients can shield the skin against UVA rays.
These vitamins may also be helpful against blue light because UVA and blue light are close neighbors on the light spectrum. 25,37

| CON CLUS ION
The majority of frequently used electronic devices, including smartphones, computers, and other devices, generate blue light. The wavelength and intensity of blue light exposure have been proved to have a significant impact on the skin's reaction. In many dermatological illnesses, it has a curative impact with minimal exposure; on the other hand, long-term exposure has numerous detrimental effects, including DNA damage, oxidative stress, increased melanogenesis leading to pigmentation, photoaging, etc. In the near future, as we learn more about the mechanism of harm that blue light exposure causes to the skin, we may anticipate seeing a rise in the number of compounds introduced for blue light protection and new methodologies created to test goods for blue light protection claims. People who are frequently exposed to blue light pollution must take various precautionary steps because exposure to blue light is inevitable.

DATA AVA I L A B I L I T Y S TAT E M E N T
Data sharing not applicable to this article as no datasets were generated or analysed during the current study.

D I SCL A I M ER
We confirm that the manuscript has been read and approved by all the authors, that the requirements for authorship as stated earlier in this document have been met and that each author believes that the manuscript represents honest work.

E TH I C A L A PPROVA L
No ethical approval was required as this research did not involve human subjects or animals.