Impact of Long‐Wavelength Ultraviolet A1 and Visible Light on Light‐Skinned Individuals

Different therapeutic approaches in melasma: advances and limitations

Melasma is a chronic hyperpigmentation skin disorder that is more common in the female gender. Although melasma is a multifactorial skin disorder, however, sun-exposure and genetic predisposition are considered as the main etiologic factors in melasma occurrence. Although numerous topical and systemic therapeutic agents and also non-pharmacologic procedural treatments have been considered in melasma management, however, the commonly available therapeutic options have several limitations including the lack of sufficient clinical effectiveness, risk of relapse, and high rate of unwanted adverse drug reactions. Recruitment of nanotechnology for topical drug delivery in melasma management can lead to enhanced skin penetration, targeted drug delivery to the site of action, longer deposition at the targeted area, and limit systemic absorption and therefore systemic availability and adverse drug reactions. In the current review, first of all, the etiology, pathophysiology, and severity classification of melasma have been considered. Then, various pharmacologic and procedural therapeutic options in melasma treatment have been discussed. Afterward, the usage of various types of nanoparticles for the purpose of topical drug delivery for melasma management was considered. In the end, numerous clinical studies and controlled clinical trials on the assessment of the effectiveness of these novel topical formulations in melasma management are summarized.

Research on Strengthening Fragile Paper with Polyvinylamine

Paper documents are an important carrier of information related to human civilization, with the reinforcement and protection of fragile paper documents being a key aspect of their protection. This research utilized amphoteric polyvinylamine polymer as a paper reinforcement agent, strengthening the Xuan paper commonly used in paper documents. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), solid-state 13C NMR, and other analytical methods were employed to compare the physical properties, micro-morphology, crystallinity, and aging resistance of the paper before and after reinforcement. Research was conducted on the effects of reinforcement, the aging resistance, and the effects on the fiber structure. The results indicate that polyethylenimine has a filling and bridging effect between the paper fibers. After treatment with polyethylenimine, there was a significant improvement in the folding endurance and tensile strength of the paper. Additionally, the paper maintains a good mechanical strength even after undergoing dry heat and humid aging.

Green approach for the fabrication of a ternary nanocatalyst (Ag-ZnONPs@Cy) for visible light-induced photocatalytic reduction of nitroarenes to aminoarenes

In recent times, the incorporation of metal oxide nanoparticles with organic dyes has piqued the interest of numerous researchers due to their diverse applications under visible light instead of UV radiation. This investigation employed a three-step methodology to fabricate cyanidin-sensitized silver-doped zinc oxide nanoparticles (Ag-ZnO@Cy). Initially, cyanidin dye was extracted from fresh black mulberry fruit, followed by the eco-friendly synthesis of Ag-ZnO nanoparticles (Ag-ZnONPs). The successful integration of the prepared cyanidin dye with Ag-ZnONPs was achieved through a straightforward, environmentally benign, and cost-efficient procedure. The resultant ternary composite underwent comprehensive characterization and confirmation utilizing various techniques, such as SEM, FT-IR, EDX, DRS, elemental mapping, and XRD. The experimental results for Ag-ZnONPs@Cy demonstrated that the nanocrystalline wurtzite exhibited spherical shapes with an average crystal size of 27.42 nm. Moreover, the photocatalytic activity of the synthesized Ag-ZnONPs@Cy was meticulously investigated under blue LED light irradiation. This inquiry encompassed examinations of catalyst amount, regeneration, stability, reusability, and the influence of light source on the hydrogenation of nitroarenes to the corresponding aminoarenes. The findings shed light on the potential of this composite for diverse photocatalytic applications.

New developments in sunscreens

Topical sunscreen application is one of the most important photoprotection tool to prevent sun damaging effects in human skin at the short and long term. Although its efficacy and cosmeticity have significantly improved in recent years, a better understanding of the biological and clinical effects of longer wavelength radiation, such as long ultraviolet A (UVA I) and blue light, has driven scientists and companies to search for effective and safe filters and substances to protect against these newly identified forms of radiation. New technologies have sought to imbue sunscreen with novel properties, such as the reduction of calorific radiation. Cutaneous penetration by sunscreens can also be reduced using hydrogels or nanocrystals that envelop the filters, or by binding filters to nanocarriers such as alginate microparticles, cyclodextrins, and methacrylate polymers. Finally, researchers have looked to nature as a source of healthier products, such as plant products (e.g., mycosporines, scytonemin, and various flavonoids) and even fungal and bacterial melanin, which could potentially be used as substitutes or enhancers of current filters.

Cutaneous interaction with visible light: What do we know?

Visible light has been used therapeutically in dermatology for years for a variety of cosmetic and medical indications, including skin rejuvenation and the treatment of inflammatory and neoplastic conditions, among others. Until recently, visible light was thought to be relatively inert compared to its spectral neighbors, ultraviolet and infrared radiation. However, recent literature has described the ability of visible light to cause erythema in light skin and pigmentary changes in individuals with darker skin types. Concern surrounding its potentially damaging cutaneous effects has been raised in both the medical community and social media outlets. In this article, we provide an evidenced-based review describing what is currently known about visible light, focusing on its role in dermatologic diseases including disorders of hyperpigmentation such as melasma and postinflammatory hyperpigmentation.

Clinical and molecular change induced by repeated low-dose visible light exposure in both light-skinned and dark-skinned individuals

BACKGROUND

Visible light (VL) is known to induce pigmentation in dark-skinned individuals and immediate erythema in light-skinned individuals. However, the effects of accumulated low-dose VL exposure across skin types are not well established.

METHODS

Thirty-one healthy subjects with light (Fitzpatrick skin types [FST] I-II, n = 13) and dark (FST V-VI, n = 18) skin types were enrolled. Subjects' buttocks were exposed daily to VL, wavelength 400-700 nm, with a dose of 120 J/cm2 at 50 mW/cm2 , for four consecutive days. Microarray using Affymetrix GeneChip (49,395 genes) was performed followed by qRT-PCR on skin samples.

RESULTS

Repeated low-dose VL irradiation induced immediate pigment darkening and delayed tanning in dark-skinned individuals while no discernable pigmentation and erythema were observed in light-skinned individuals. Top ten upregulated genes by repeated VL exposure in microarray included melanogenic genes such as tyrosinase (TYR), tyrosinase-related protein-1 (TYRP1), dopachrome tautomerase (DCT), premelanosome protein (PMEL), melan-A (MLANA), and solute carrier family 24, member 5 (SLC24A5) and genes involved in inflammation/matrix remodeling/cell signaling including chemokine (C-C motif) ligand 18 (CCL18), BCL2-related protein A1 (BCL2A1), and cartilage oligomeric matrix protein (COMP). In qRT-PCR CCL18 was upregulated in light skin with a greater extent (mean fold change ± SD; 4.03 ± 3.28, p = .04) than in dark-skinned individuals (1.91 ± 1.32, p = .07) while TYR was not significantly upregulated in both skin types.

CONCLUSION

This study highlights the genes upregulated by cumulative VL exposure involved in pigmentation, immune response, oxidation/reduction, and matrix remodeling across skin types providing relevant information on daily solar exposure.

Development of Solid Lipid Nanoparticle-Loaded Polymeric Hydrogels Containing Antioxidant and Photoprotective Bioactive Compounds of Safflower (Carthamus tinctorius L.) for Improved Skin Delivery

Safflower (Carthamus tinctorius L.) is a potent natural antioxidant because of active compounds such as quercetin (QU) and luteolin (LU). These components prevent damage to the skin caused by free radicals from UV rays. However, due to the poor solubility and transdermal permeation, the effectiveness of the compounds in showing their activity was limited. In this study, we develop solid lipid nanoparticle (SLN)-based hydrogel formulations to enhance the solubility and penetration of two bioactive compounds found in safflower petals extract (SPE). The hot emulsification-ultrasonication method was used to produce SLNs, and to obtain high antioxidant activity, 100% v/v ethanol was used in the extraction procedure. The results showed that this approach could encapsulate >80% of both QU and LU. Moreover, Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), and powder X-ray diffraction (PXRD) spectra indicated that most of the QU and LU were trapped in a lipid matrix and dispersed homogeneously at the molecular level, increasing the solubility. Additionally, SLN-hydrogel composites are able to release two lipophilic bioactive compounds for 24 h, which also demonstrated increased skin retention and penetrability of the QU and LU up to 19-fold. In vitro blood biocompatibility showed that no hemolytic toxicity was observed below 500 μg/mL. Accordingly, the formulation was considered safe for use. Sun protective factor (SPF) test shows a value above 15, showing an excellent promising application as the photoprotective agent to prevent symptoms associated with photoinduced skin aging.

Disorders of hyperpigmentation. Part II. Review of management and treatment options for hyperpigmentation

Key challenges in the management of pigmentary disorders such as melasma and postinflammatory hyperpigmentation are their resistance to treatment, tendency to recur after treatment, and the risk of exacerbating hyperpigmentation with many treatment modalities. The second article in this 2-part continuing medical education series on pigmentary disorders focuses on the evidence behind medical and procedural treatments of dyschromias, including photoprotection, topical lightening agents, oral agents, chemical peels, and laser therapy.

The cutaneous effects of blue light from electronic devices: a systematic review with health hazard identification

The biologic effects of visible light, particularly blue light, on the skin at doses and irradiances representative of sunlight have been established. Recent research studies investigated the effects of blue light (BL) from electronic screen devices; however, it is unclear if the evidence can be generalized to real life. The aim of this systematic review was to evaluate available evidence regarding clinical effects of BL emitted from electronic devices on human skin using the framework established by the Office of Health Assessment and Translation (OHAT). A systematic literature search was conducted by two librarians in Ovid MEDLINE, Embase.com, and Web of Science for relevant articles published from 1946 to March 2022. In vitro and in vivo studies that investigated the effects of BL from electronic devices on skin were included. From the 87 articles gathered from database searches and 1 article identified from citation search, only 9 met the inclusion criteria (6 in vitro and 3 in vivo studies). Human and animal literature with the highest level of evidence ratings were considered with mechanistic data to form one of five human hazard identifications for each outcome category using the OHAT protocol: (1) known, (2) presumed, (3) suspected, (4) not classifiable, or (5) not identified to be a hazard to humans. Literature-based evidence integration did not identify exposure to BL from electronic devices as a hazard to skin pigmentation, redness, yellowness, or melasma exacerbation. Exposure to BL from electronic devices was not classified as a skin photoaging hazard. Low confidence in representative exposure characterization drove high OHAT risk-of-bias ratings for the majority of included studies. While these conclusions hold true for the limited existing data, a larger number of future studies with high-confidence evidence are needed to verify and strengthen hazard identification conclusions.

Melasma: The need for tailored photoprotection to improve clinical outcomes

BACKGROUND/PURPOSE

Melasma is a frequent photoexacerbated hyperpigmentary disorder, which can significantly impact on the quality of life. We sought to review the pathogenesis of melasma, and the role of photoprotection in the prevention and treatment of this disorder.

METHODS

We conducted a narrative review of the literature. We performed literature searches with PubMed from January 1990 to December 2021 using the keywords "melasma," "pathogenesis," "ultraviolet radiation," "visible light," "photoprotection," and "sunscreens."

RESULTS

The physiopathology of melasma includes a complex interaction between genetics, sex hormones, and sun exposure. Visible light, in particular high-energy visible light (HEVL), and long-wave UVA (UVA1) play a key role in melasma pathophysiology, and recent research suggests that melasma shares many features with photoaging disorders. Melasma disproportionately affects dark-skinned individuals. Some 30% to 50% of South Americans and Asians, among other ethnicities, can present with melasma. Dark-skinned patients take fewer photoprotective measures. Also, the majority of melasma patients do not adequately follow photoprotection recommendations, including the application of sunscreen. Intensive use of a broad-spectrum sunscreen can prevent melasma in high-risk individuals, can lessen melasma severity (associated or not with depigmenting agents), and can reduce relapses.

CONCLUSIONS

Due to the physiopathology of melasma, sunscreens should be broad-spectrum with high sun protection factor, and provide high protection against UVA1 and VL. Sunscreens should be cosmetically acceptable and leave no white residue. Tinted sunscreens are an excellent choice, as pigments can protect from HEVL and UVA1, and may provide camouflage, but they must offer colors that match the skin tone of each patient.

Evaluation of a Sunscreen Product Compared with Reference Standards P3, P5 and P8 in Outdoor Conditions: a Randomized, Double-Blinded, Intra-individual Study in Healthy Subjects

INTRODUCTION

The shortcomings of standardized sunscreen testing have been discussed in recent years, noting differences between how sunscreens perform in indoor clinical (in vivo) laboratory testing compared with real-life conditions. We previously developed an outdoor clinical method for ranking sunscreens by performance level. We used this method to test the performance of a new broad-spectrum sunscreen against International Organization for Standardization (ISO) reference products P3, P5 and P8.

METHODS

Sixty-five healthy volunteers with individual typology angle (ITA) ≥ 28° (light to intermediate skin colour) participated in an outdoor study in Mauritius. Test areas were marked on their backs, which were treated with the different products: one commercially available broad-spectrum sun protection factor (SPF) 50 sunscreen [investigational product (IP)] and the three reference products P3 (SPF 15), P5 (SPF 30) and P8 (SPF 50+) from ISO norm 24444:2019 for SPF testing. The test areas were exposed for 2-3 h, depending on the baseline skin colour. They were also compared with an unprotected positive control area and a non-exposed negative control area. Clinical and colorimetry assessment of erythema and pigmentation were performed at 24 h and 8 days, respectively.

RESULTS

Overall, according to this outdoor clinical testing method, the sunscreens' efficacy was ranked in an appropriate order given their established SPF levels, with higher SPFs giving greater protection against erythema and pigmentation. Between the different levels of SPF, the differences were statistically significant, for both clinical and colorimetry assessments. The new broad-spectrum SPF 50 IP performed similarly to the SPF 50+ (P8) reference product. Even the highest SPF products, SPF 50 and SPF 50+, had some instances of photoprotection failure.

CONCLUSION

These findings confirm the feasibility of this outdoor clinical testing method in ranking sunscreens and provide further evidence, in addition to standardized SPF and UVA protection factor (UVAPF) testing, on how this new broad-spectrum SPF 50 sunscreen performs in extreme outdoor solar exposure: in line with reference product P8 (SPF 50+).

TRIAL REGISTRATION NO

ISRCTN95394014.

The Damaging Effects of Long UVA (UVA1) Rays: A Major Challenge to Preserve Skin Health and Integrity

Within solar ultraviolet (UV) light, the longest UVA1 wavelengths, with significant and relatively constant levels all year round and large penetration properties, produce effects in all cutaneous layers. Their effects, mediated by numerous endogenous chromophores, primarily involve the generation of reactive oxygen species (ROS). The resulting oxidative stress is the major mode of action of UVA1, responsible for lipid peroxidation, protein carbonylation, DNA lesions and subsequent intracellular signaling cascades. These molecular changes lead to mutations, apoptosis, dermis remodeling, inflammatory reactions and abnormal immune responses. The altered biological functions contribute to clinical consequences such as hyperpigmentation, inflammation, photoimmunosuppression, sun allergies, photoaging and photocancers. Such harmful impacts have also been reported after the use of UVA1 phototherapy or tanning beds. Furthermore, other external aggressors, such as pollutants and visible light (Vis), were shown to induce independent, cumulative and synergistic effects with UVA1 rays. In this review, we synthetize the biological and clinical effects of UVA1 and the complementary effects of UVA1 with pollutants or Vis. The identified deleterious biological impact of UVA1 contributing to clinical consequences, combined with the predominance of UVA1 rays in solar UV radiation, constitute a solid rational for the need for a broad photoprotection, including UVA1 up to 400 nm.

Formulation of a new broad-spectrum UVB + UVA and blue light SPF50+ sunscreen containing Phenylene Bis-Diphenyltriazine (TriAsorB), an innovative sun filter with unique optical properties

Accumulating evidence from numerous comprehensive studies has demonstrated that blue light, in particular high-energy visible light, can exert a range of harmful effects on skin cells. These forms of radiation are now known to be able to trigger oxidation reactions, DNA damage, erythema and pigmentary changes, and may also be associated with photoaging. Sunscreens protecting the skin from only ultraviolet (UV)-B and UVA rays can therefore no longer be regarded as sufficient to help prevent skin damage from sunlight, and products containing filters that can provide broad-spectrum photoprotection are required. To meet this need, a new sunscreen formulation that provides photoprotection against solar radiation with wavelengths ranging from UV to visible light has been developed, using an innovative organic sun filter with unique optical properties: phenylene bis diphenyltriazine (TriAsorB™). This article outlines the development and characteristics of this innovative filter and describes new key results from studies performed to assess the effectiveness and safety of the filter and the new sunscreen product. The studies conducted so far demonstrate that the filter has a good human and environmental safety profile. In addition, the sunscreen, which contains TriAsorB in combination with three other UV filters to offer broad-spectrum sun protection with a high sun protection factor (SPF50⁺ ), appears to effectively prevent multiple forms of cellular photodamage, in particular blue light-induced oxidatively generated DNA lesions. Overall, the available data indicate that regular use of the TriAsorB-containing sunscreen could help prevent solar radiation-induced skin damage and the development of signs of premature skin aging, as well as photodermatoses caused or exacerbated by visible light.

Evaluation of efficacy of antioxidant-enriched sunscreen prodcuts against long wavelength ultraviolet A1 and visible light

OBJECTIVE

The synergistic effects of VL and long wavelength UVA1 (VL+UVA1, 370-700 nm) on inducing pigmentation and erythema in skin have been demonstrated and linked to exacerbation of dermatologic conditions including melasma and post-inflammatory hyperpigmentation. This study aims to compare the photoprotection of organic sunscreens enriched with antioxidant (AO) combinations against VL+UVA1 induced biologic effects. The efficacy was compared to that offered by a commercially available tinted sunscreen.

METHODS

Ten healthy adult subjects with Fitzpatrick skin phototypes IV-VI were enrolled (nine completed). VL+UVA1 dose of 380 J/cm² was utilized. Assessment methods were polarized photography, investigator global scoring, and diffuse reflectance spectroscopy (DRS). Measurements were obtained at baseline and immediately, 24 hours, and 7 days after irradiation.

RESULTS

Sites treated with tinted sunscreen product had significantly less pigmentation compared with untreated but irradiated skin at all time points. However, DRS results demonstrated that the 5-AO sunscreen performed comparably or better than all sunscreens tested with relatively lower dyschromia, delayed erythema and pigmentation.

CONCLUSION

These results highlight the potential of AO enriched sunscreens to be photoprotective against VL+UVA1. The combination of efficacy and the cosmetic appearance of this product may provide wider acceptability which is crucial considering the limited available means of protection against this waveband.

PHOTOPROTECTION FOR ALL: CURRENT GAPS AND OPPORTUNITIES

The effects of solar radiation on human skin differ based on skin phototype, the presence or absence of photodermatoses, biological capacity to repair DNA damage, wavelength, intensity of sun exposure, geographic latitude, and other factors, underscoring the need for a more tailored approach to photoprotection. To date, the focus of photoprotection guidelines has been to prevent sunburn and DNA damage induced by ultraviolet (UV) radiation, both UVB and UVA; however, several recent studies have shown that visible light (VL) also generates reactive oxygen and nitrogen species that can contribute to skin damage and pigmentation on the skin, particularly in people of color. Therefore, dark-skinned individuals, while naturally better protected against UVB radiation by virtue of high eumelanin content in melanocytes, may need additional protection from VL-induced skin damage. The current options for photoprotection products need to expand, and potential strategies against VL include the addition of iron oxide, titanium dioxide, and biologically relevant antioxidants to sunscreen formulations, as well as supplementation with orally active antioxidants.

Impact of visible light on skin health: The role of antioxidants and free radical quenchers in skin protection

Until recently, the primary focus of photobiology has centered on the impact of UV radiation on skin health, including DNA damage and oncogenesis; however, the significant effects of visible light (VL) on skin remain grossly underreported. VL has been reported to cause erythema in individuals with light skin (Fitzpatrick skin types [FSTs] I-III) and pigmentary changes in individuals with dark skin types (FSTs IV-VI). These effects have importance in dermatologic diseases and potentially play a role in conditions aggravated by sun exposure, including phototoxicity in patients with FSTs I to III and post-inflammatory hyperpigmentation and melasma in patients with FSTs IV to VI. The induction of free radicals, leading to the generation of reactive species, is one driving mechanism of VL-induced skin pathologies, leading to the induction of melanogenesis and hyperpigmentation. Initial clinical studies have demonstrated the effectiveness of topical sunscreen with antioxidant combinations in inhibiting VL + UV-A1-induced erythema in FSTs I to III and reducing pigmentation in FSTs IV to VI. Antioxidants may help prevent the worsening of pigmentary disorders and can be incorporated into photoprotective strategies. It is essential that dermatologists and the public are aware of the impact of VL on skin, especially in patients with skin of color, and understand the available options for VL protection.

Mitigating Visible Light and Long Wavelength UVA1-induced Effects with Topical Antioxidants

The role of topical antioxidants (AOs) on visible light plus ultraviolet A1 (VL+UVA1)-induced skin changes were evaluated. Twenty subjects with skin phototypes (SPTs) I-VI had placebo and concentrations of an AO blend applied to their back (AO 0.5%, 1.0% and 2.0%). Treated and control sites were irradiated with VL+UVA1. Colorimetric and diffuse reflectance spectroscopy (DRS) assessments were performed immediately, 24 h and 7 days after irradiation. Subjects with SPT I-III had erythema that faded within 24 h, while SPT IV-VI had persistent pigmentation. SPT I-III demonstrated significantly less erythema at the 2% AO site while SPT IV-VI demonstrated significantly less immediate pigmentation at 2% AO site and less pigmentation (approaching significance, P = 0.07) on day 7 compared with control. Immunohistochemistry from biopsies of 2% AO and placebo at 24 h did not demonstrate a significant change in COX-2 or MART-1 for any SPT. There was a decrease in cyclin D1 for SPT IV-VI which was approaching significance (P = 0.06) but not for SPT I-III. The results indicate that topical AO inhibits erythema in SPT I-III and reduces pigmentation in SPT IV-VI caused by VL+UVA1. AO may help prevent worsening of pigmentary disorders and should be incorporated into photoprotection.

Outdoor sunscreen testing with high-intensity solar exposure in a Chinese and Caucasian population

BACKGROUND

Currently, sunscreens' sun protection factor (SPF) and ultraviolet (UV) A protection are tested separately under indoor conditions, without considering external conditions that may affect performance. Studies are often conducted in Caucasian individuals; other racial groups may respond differently.

METHODS

An outdoor, double-blind, intra-individual study was performed in 63 healthy Chinese and Caucasian volunteers in Singapore. Subjects underwent one outdoor sun exposure lasting 2-3 hours. ISO reference products P3 (SPF 15), P5 (SPF 30), and P8 (SPF 50+) applied at 2 mg/cm² were compared against each other and against an untreated exposed area (positive control) and an unexposed area (negative control). Endpoints were investigator global assessment (IGA) of erythema at 24 hours, IGA of pigmentation at 1 week, and colorimetry (a*, L*, and ITA) at 24 hours and 1 week.

RESULTS

Clinical erythema and pigmentation scores were statistically significantly different among the three sunscreens, with the highest SPF product providing the highest protection, confirming the discriminatory capacity of the model used. Colorimetric assessment correlated well with clinical evaluation.

CONCLUSION

This study confirmed the feasibility of ranking sunscreens (at 2 mg/cm² ) based on clinical effects of high-intensity outdoor solar radiation. Larger studies are needed to look at differences in erythema and pigmentation reactions between Chinese and Caucasian individuals, which could be relevant for photoprotection.

Photoprotection of the Skin from Visible Light‒Induced Pigmentation: Current Testing Methods and Proposed Harmonization

Visible light (VL) can induce pigmentary alterations, especially in dark-skinned individuals, and exacerbate photodermatoses and pigmentary disorders. Currently, there is no standardized method for assessing sunscreen protection against VL. On the basis of a critical review of published in vitro and in vivo methods, a VL photoprotection assessment method based on pigmentation is proposed.

Visible light. Part I: Properties and cutaneous effects of visible light

Approximately 50% of the sunlight reaching the Earth's surface is visible light (400-700 nm). Other sources of visible light include lasers, light-emitting diodes, and flash lamps. Photons from visible light are absorbed by photoreceptive chromophores (e.g., melanin, heme, and opsins), altering skin function by activating and imparting energy to chromophores. Additionally, visible light can penetrate the full thickness of the skin and induce pigmentation and erythema. Clinically, lasers and light devices are used to treat skin conditions by utilizing specific wavelengths and treatment parameters. Red and blue light from light-emitting diodes and intense pulsed light have been studied as antimicrobial and anti-inflammatory treatments for acne. Pulsed dye lasers are used to treat vascular lesions in adults and infants. Further research is necessary to determine the functional significance of visible light on skin health without confounding the influence of ultraviolet and infrared wavelengths.

Impact of ultraviolet radiation and exposome on rosacea: Key role of photoprotection in optimizing treatment

Background

Pathophysiology of rosacea is not completely understood and involves a complex interaction among genetics, ultraviolet (UV) light, microorganisms, impaired skin barrier, neuronal and vascular dysfunction, and immune system disruption.

Aims

To describe the etiology of rosacea with an emphasis on the role of UV radiation and exposome, and to review the importance of non‐pharmacologic strategies focusing on photoprotection.

Methods

We conducted a narrative review of the literature. We performed literature searches with PubMed from January 1990 to November 2020 using the keywords “rosacea”, “pathogenesis”, “ultraviolet radiation”, “exposome”, “photoprotection”, “sunscreens” and “non‐pharmacologic agents”. The search was limited to English, Spanish, and French language articles.

Results

Several environmental factors such as UV light, diverse microorganisms, air pollution, tobacco smoking, nutrition, and psychological stress showed to trigger or worsen rosacea. UV radiation was reported to induce pro‐inflammatory, pro‐angiogenic, and pro‐fibrotic responses. We found 6 original articles about the impact of sunscreens on rosacea. The use of sunscreens containing ingredients with emollient, anti‐inflammatory, and/or vasoregulatory properties was shown to significantly improve symptomatology.

Conclusion

UV radiation and the exposome play a key role in the development of rosacea. UV light is implicated in all significant aspects of rosacea: skin inflammation, neoangiogenesis, telangiectasia, and fibrosis, and may even initiate rosacea. While the use of sunscreens is widely recommended, the literature on the impact of photoprotection in rosacea is scarce. Adequately formulated sunscreens could not only provide the required level of photoprotection, but may also help to mitigate the barrier dysfunction, neutralize facial redness (tinted sunscreens), and decrease inflammation and vascular dysfunction.

Photoprotection beyond ultraviolet radiation: A review of tinted sunscreens

Ultraviolet radiation and visible light both have biologic effects on the skin. Visible light can induce erythema in light-skinned individuals and pigmentation in dark-skinned individuals. Broad-spectrum sunscreens protect against ultraviolet radiation but do not adequately protect against visible light. For a sunscreen to protect against visible light, it must be visible on the skin. Inorganic filters (also known as mineral filters), namely, zinc oxide and titanium dioxide, are used in the form of nanoparticles in sunscreens to minimize the chalky and white appearance on the skin; as such, they do not protect against visible light. Tinted sunscreens use different formulations and concentrations of iron oxides and pigmentary titanium dioxide to provide protection against visible light. Many shades of tinted sunscreens are available by combining different amounts of iron oxides and pigmentary titanium dioxide to cater to all skin phototypes. Therefore, tinted sunscreens are beneficial for patients with visible light-induced photodermatoses and those with hyperpigmentation disorders such as melasma and postinflammatory hyperpigmentation.

Visible light in photodermatology

Until recently, visible light (VL) had been regarded to be without significant photobiologic effect on the skin. Updated research suggests that this is not the case and the measurable effect of visible light on the skin is being documented in all skin types. Recent studies have demonstrated that in dark-skinned individuals, visible light can induce more intense and longer lasting pigmentation of the skin compared to UVA1. This effect was potentiated when VL was combined with a small percentage of ultraviolet A1 radiation (UVA1). Further, the combination of VL + UVA1 was also able to induce erythema in light-skinned individuals, a novel finding since the erythemogenic spectrum of sunlight had primarily been attributed to ultraviolet B (UVB) and short wavelength UVA (320-340 nm). Based on these findings, VL and UVA1 may also potentially play a role in conditions aggravated by sun exposure such as phototoxicity in light-skinned patients and post-inflammatory hyperpigmentation and melasma, especially in dark-skinned individuals. Currently available organic (chemical) UV filters are not sufficient to protect the skin from the effect of VL. VL is emerging as a key player in photodermatology and additional research is needed on the cutaneous effects of VL, as well as the development of filters and other means of photoprotection against the harmful effects of the VL spectrum. The aim of this manuscript is to review the literature on the cutaneous effects of VL as well as to highlight areas of dermatology where VL may play an important role.