The Impact of Blue Light & High-Energy Visible Light

Blue light, is also known as high-energy visible (HEV) light and is the most energetic part of the visible light spectrum (380 - 700 nm) with wavelengths ranging from indigo or ultramarine light 420-440 nanometers, blue light 450-495 nanometers to cyan light 480 - 520 nanometers. Blue light has lower energy than ultraviolet (UV) radiation (280–400 nm) and can reach further into the dermis, up to the depth of 1 mm. [1] Sunlight is the primary natural source of blue light. Up to 50% of the damaging oxidative stress in human skin is generated in the VIS spectrum and the other 50% by UV light [2], contributing to premature ageing, ox-inflammageing and hyperpigmentation like age spots.
 
Blue light from electronic devices
The use of electronic devices has led to increased exposure to artificial blue light sources, however the amount of blue light emitted during the conventional use of electronic devices is by far not enough to trigger harmful skin effects. If you sit in front of a monitor uninterrupted for a week at a distance from the screen of approximately 30 cm, this would be the same as the blue light intensity of spending one minute outside on a sunny day in Hamburg Germany at around midday at midsummer. If you hold a smartphone right next to the skin, the intensity does increase, but it would still take approximately 10 hours of uninterrupted use to match the effect on the skin of just one minute of sunlight. The emissions from electronic devices are barely noticeable in comparison to natural blue light directly from the sun and are, thus negligible. However, blue light or HEV light from sunlight can be harmful for skin. Dr Ludger Kolbe Chief Scientist for Photobiology and his team at Beiersdorf AG did pioneering research regarding the harmful effects of HEVIS. [3-4]

I would also like to take the opportunity to debunk an important myth at the start of this article as infrared or near infrared light does not induce damaging free radicals (even in high amounts), there is no such thing "infra-ageing" as a result or IR and in fact red light photobiomodulation supports skin rejuvenation. Read more

Direct effects of blue light and HEV Light on skin
Blue light and HEV light can have both beneficial and detrimental effects on the skin. The most significant direct effects are mediated through their interaction with chromophores, such as flavins, porphyrins, and opsins, which can trigger the overproduction of reactive oxygen species (ROS), reactive nitrogen species (RNS). and hyperpigmentation. Reactive oxygen and nitrogen species cause DNA damage and modulate the immune response. [1]

This oxidative stress can lead to:
Photo-ageing: Exposure to blue light and HEV light can induce premature skin aging, causing wrinkles, fine lines, and loss of elasticity.
Hyperpigmentation: Blue light and HEV light can stimulate melanin production, leading to uneven skin tone and the development of age spots or other forms of hyperpigmentation.
DNA Damage: The ROS and RNS generated by blue light and HEV light can cause DNA damage, plus potentially increase the risk of skin cancer.
Inflammation: The oxidative stress triggered by blue light and HEV light can cause an inflammatory response in the skin, exacerbating conditions like acne, eczema, and psoriasis.

Molecular and physiological mechanisms of direct blue light effects on the skin [1]

1. ROS generation 
2. Carotenoid degradation. Carotenoids are one of the key antioxidants protecting from ROS damage. Most of the carotenoids found in the skin absorb radiation in the blue section of the spectrum. The highest concentration of carotenoids in the skin is found in the stratum corneum, the outermost skin layer that serves as permeability barrier, thus preventing transepidermal water loss. 
3. Flavin degradation (the main chromophores responsible for blue light-induced ROS overproduction and abundant in mitochondria)
4. DNA damage (keratinocytes + melanocytes) both oxidative and cyclobutane-pyrimidine-dimer (CPD) DNA lesions
5. Whole genome DNA methylation (epigenetic modification)  
6. Decreased proliferation of fibroblasts and keratinocytes, however to the contrary also stimulation of proliferation and differentiation keratinocytes 
7. Decreased expression TP73  the gene involved in proliferation, in primary human keratinocytes and melanocytes
8. Decreased cell viability 
9. Apoptosis 
10. Decreased ATP synthesis Read more 
11. Decreased expression of genes regulating mitochondrial function  & blue light-induced ROS generation damages mitochondrial DNA and disrupts respiration
12. Increased EGFR phosphorylation and reduced EGFR expression (keratinocytes)
13. Downregulation of TGF-β signaling fibroblasts 
14. Increased pro-inflammatory cytokines 
15. Increased COX-2 levels 
16. Delayed recovery of epidermal permeability barrier
17. MMP1-release (collagenase 1) responsible for collagen type I and III degradation
18. Decreased procollagen 1 content (fibroblasts) 
19. Decreased collagen lattice contractility
20. Increased protein carbonylation (one of the most harmful irreversible oxidative protein modifications and considered a major hallmark of oxidative damage)
21. Hyperpigmentation and age spots (compared with UV, blue light produced darker hyperpigmentation that lasted longer in phototypes IV-VI).  While both UV and blue light cause hyperpigmentation via ROS generation, only blue light causes hyperpigmentation via opsin stimulation.  Opsins are a class of photosensitive G protein-coupled receptors, which regulate various signaling cascades found in retina and skin, hence this is why both glasses (although according to some studies blue light glasses don't do their job properly [14]) and topical products protecting from damaging blue light make sense. Blue light irradiation over 5 consecutive days results in increased perinuclear vacuolization in keratinocytes and an increased number of melan-A-positive cells. Blue light irradiation increased melanin production, oxygen saturation, and hemoglobin content in female volunteers. When exposed to blue light, OPN3 initiated a signaling cascade that leads to increases in the enzymes tyrosinase and dopachrome tautomerase (DCT) that are responsible for melanogenesis. Blue light-induced hyperpigmentation is more pronounced and persistent in people with darker skin (Fitzpatrick types III–VI), likely because they have higher levels of tyrosinase–DCT complexes than people with lighter skin (Fitzpatrick types I and II). 
22. Erythema (redness) most pronounced in individuals with lighter skin types (Fitzpatrick skin types I-III) - 17% compared to UV
23. Photolytic release of NO from nitrosated proteins (can cause significant local vasodilation and possibly even to reduce systemic blood flow)
24. Decreased expression of antimicrobial peptides (AMPs eliminate pathogenic micro-organisms, including bacteria, fungi, and viruses)
25. Blue light has a greater contribution to ROS generation from carbonylated proteins located in the stratum corneum than UV. CPs are detected in a higher frequency at sun-exposed sites of the skin in elderly subjects. 
26. At wavelengths of 412–426 nm and high fluences, blue light is cytotoxic to human keratinocytes and skin-derived endothelial cells.

The severity of these effects can vary depending on skin type, duration and intensity of exposure.

Indirect effects of blue light and HEV Light on skin
Blue light and HEV light can also have indirect effects on the skin by disrupting the body's circadian rhythms. This occurs via both the central mechanism, which involves stimulation of light-sensing receptors located in the retina, and via the peripheral mechanism, which involves direct interaction with skin cells. By disrupting the normal circadian rhythm, blue light can negatively affect the skin's natural overnight repair and regeneration processes. [1] 

The circadian rhythm has been shown to affect multiple cellular and physiological processes occurring in the skin:

• Normal keratinocyte proliferation peaks at night. 
• The rate of blood flow, permeability to both hydrophilic and lipophilic compounds and transepidermal water loss are all higher in the evening and at night than during the day.
• Sebaceous gland activity is highest during the day and decreases in the evening and at night.
• Repair of sunlight-induced DNA damage also mostly occurs at night. 

Topical dermatological skin care products containing bio-active ingredients supporting skin's repair and regeneration mechanisms are thus more effective when used later in the day.

Molecular mechanisms of indirect effects of blue light on the skin [1]

1. Decreases plasma melatonin
2. Delayed melatonin onset
3. Decreased melatonin duration
4. Decreased melatonin exposure
5. Decreased subjective sleepiness
6. Decreased proximal skin temperature
7. Increased cortisol level
8. Decreased per 1 transcription
9. Alteration of ECTO-NOX oscillatory pattern
10. Decreased keratin-1 & keratin-10
11. Elastic fiber network disruption

A new study by researchers from the University of Basel, published in Nature Human Behavior 2024 however suggests that blue light might not impact our "internal clock". 

Ideal daytime & nighttime skin care regimen
When considering cosmetic interventions, a strategy of daytime protection plus defense and night-time repair may be optimal. The skin's own repair mechanisms, such as base excision repair and nucleotide excision repair, attempt to mitigate blue light induced DNA damage. [12]

Daytime protection plus defense
Of course prevention and/or reduction of blue light exposure from sunlight is key. Reduce the time spent on electronic devices, especially before bedtime, can help minimize the disruption of circadian rhythms and the indirect effects of blue light and HEV light on the skin.
Against premature ageing and hyperpigmentation an evidence based effective approach could be the daily use of tinted broadband sunscreen preferably containing Licochalcone A (the most effective anti-oxidant reducing damaging free radical activity from both UV and blue light and moreover protects against collagenase MMP-1 expression) strengthening skin's biological defense [4-5-6-7], while iron oxides in colour pigments provide physical protection against blue light (like zinc oxide and titanium dioxide). Against hyperpigmentation there are (tinted) sunscreens which on top contain the most potent human tyrosinase inhibitor found in dermatological skin care called Thiamidol® [8-9] and one of the 3 ingredients in the "new Kligman Trio" (NT)  [18] and Glycyrrhetinic Acid which supports skin's DNA repair and skin pigmentation [10] and inhibits hyaluronidase activity (HYAL1). Most regular sun filters used in sunscreen don't offer any protection against blue light, however according to the website of BASF the chemical UV filters Tinosorb® A2B and Tinosorb® M can reduce the exposure to blue light. [11]

Scattering and absorption of blue light [5]
The penetration depth of visible light is influenced by the reflection, scattering, and absorption mediated not only by the skin’s physical barrier but also by the VL chromophores in the skin and Fitzpatrick skin or photo-type (FST). The primary VL-scatter and absorption molecules in the skin include hemoglobin, melanin, bilirubin, carotene, lipids, and other structures, including cell nuclei and filamentous proteins like keratin and collagen. Melanin and keratins are the primary VL absorbers and scatterers in the epidermis, while hemoglobin is the dominant absorber, and collagen is the major VL scatter in the dermis. Melanin's absorption spectrum ranges from 200 to 900 nm, with the peak absorption varying based on melanin moiety. This means that individuals with darker skin types, which have higher melanin content, are more prone to hyperpigmentation from blue light or VIS due to the greater absorption and scattering of VIS in their skin on top of the previously mentioned higher levels of tyrosinase–DCT complexes leading to increased melanogenesis, leading to both transient and long-lasting pigmentation [13],  dependent upon the total dose and exacerbation of melasma especially in individuals with FSTs III to VI. 

Blue light tanning
Recent data demonstrate synergistic effects between VL and UV-A on erythema and pigmentation. VL-induced pigmentation is more potent and more sustained than UVA1-induced pigmentation in darker skin tones.Typically, three mechanisms are involved in the responsive reaction of melanocytes to VL, with increased melanin content: immediate pigment darkening (IPD), persistent pigment darkening (PPD), and delayed tanning (DT). [15] Read more. VL can also exacerbate post inflammatory hyperpigmentation (study with FST IV and V). [16] 

Blue light therapy
While the detrimental effects of blue light and HEV light on the skin have been well-documented, these wavelengths have also shown promise in the treatment of certain skin conditions. In controlled clinical settings, blue light has been used to:
Treat Acne: Blue light can reduce the growth of Propionibacterium acnes, the bacteria responsible for acne, and has an anti-inflammatory effect.
Manage Psoriasis and Atopic Dermatitis: Blue light has been found to have an anti-inflammatory and antiproliferative effect, making it potentially beneficial for the treatment of these chronic inflammatory skin diseases.
Reduce Itch: Some studies have suggested that blue light may help alleviate the severity of itching in certain skin conditions.
Vitiligo:  Blue light therapy via LEDs can stimulate repigmentation in patients with vitiligo with minimal adverse events, however larger studies are needed. [17] 
The optimal protocols for blue light therapy are still being developed, and the long-term safety of this treatment modality requires further investigation and should not be initiated without HCP recommendation and monitoring.

Overall, the research suggests that prolonged or excessive exposure to high-energy blue light, can have negative long-term effects on skin structure, function, and appearance in all phototypes. As our understanding of the individual variations in skin's response to blue light exposure deepens, the development of personalised or tailored effective solutions become increasingly more tangible. Always consult a qualified healthcare professional or dermatologist to determine what the most suitable approach is for your particular skin condition and rejuvenation goals. 

Take care!
​Anne-Marie

References

1. Skin Pharmacol Physiol. Direct and Indirect Effects of Blue Light Exposure on Skin: A Review of Published Literature Orawan Suitthimeathegorn et al. 2022
2. Methods, Effects on detection of radical formation in skin due to solar irradiation measured by EPR spectroscopy
   Stephanie Albrecht et al. 2016
3. EADV Congress, Paris, France 2018, Poster No. P1672. Assessment of hazard potential of high-energy visible light from electronic devices for the skin. Batzer J, Eggers K, Kolbe L, Weise J. 
4. High-energy visible light at ambient doses and intensities induces oxidative stress of skin—Protective effects of the antioxidant and Nrf2 inducer Licochalcone A in vitro and in vivo Tobias Mann et al. 2019
5. Journal of the American Academy of Dermatology Impact of visible light on skin health: The role of antioxidants and free radical quenchers in skin protection. Henry W. Lim MD et al. 2022
6. EADV Poster 2018 Licochalcone A protects from reactive oxygen species and matrix metalloproteinase-1 expression induced bz high-energy visible light irradiation in vitro Ladewig S. et al.
7. Experimental Dermatology, Licochalcone A activates Nrf2 in vitro and contributes to licorice extract-induced lowered cutaneous oxidative stress in vivo Jochen Kühn et al. 2014
8. J Invest Dermatol. Next Time, Save Mushrooms for the Pizza! Thomas J Hornyak 2018
9. J Invest Dermatol. Inhibition of Human Tyrosinase Requires Molecular Motifs Distinctively Different from Mushroom Tyrosinase
   Tobias Mann et. al 2018
10. Journal of Investigative Dermatology Conference-paper: 39th Annual European Society for Dermatological Research: Glycyrrhetinic Acid: A Novel Modulator of Human Skin Pigmentation and DNA-Repair M. Hong et a. 2009
11. BASF https://www.personal-care.basf.com/core-competencies/all-about-sun/sunlight/blue-light-exposed
12. Photodermatol Photoimmunol Photomed Blue light induces DNA damage in normal human skin keratinocytes Cécile Chamayou-Robert et al. 2022
13. Pigment Cell Melanoma Res. Differences in visible light-induced pigmentation according to wavelengths: a clinical and histological study in comparison with UVB exposure Luc Duteil et a. 2014
14. Cochrane Database of Systematic Reviews Review - Intervention Blue‐light filtering spectacle lenses for visual performance, sleep, and macular health in adults Sumeer Singh et al. 2023
15. J Clin Med. The Emerging Role of Visible Light in Melanocyte Biology and Skin Pigmentary Disorders: Friend or Foe? Xuanxuan He et al. 2023
16. Journal of the American Academy of Dermatology Cutaneous interaction with visible light: What do we know? Cohen MD et al 2023 
17. Review Photodermatol Photoimmunol Photomed A focused review of visible light therapies for vitiligo Mitchell J Winkie 2024
18. J Eur Acad Dermatol Venereol. Efficacy and safety of a novel triple combination cream compared to Kligman's trio for melasma: A 24-week double-blind prospective randomized controlled trial Clémence Bertold et al. 2023

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