Clinical Evaluation of Next-generation, Multi-weight Hyaluronic Acid Plus Antioxidant Complex-based Topical Formulations with Targeted Delivery to Enhance Skin Rejuvenation.

Introduction: Hyaluronic acid (HA) has become a commonly used ingredient in many topical products due to its strong humectant properties and essential role in skin hydration; however, limitations of delivery of HA to only the surface of skin has hindered leveraging the full capacity of HA biology necessary for skin rejuvenation. Here, we describe the clinical efficacy data of a set of novel next-generation, multi-weight HA plus antioxidant complex-based topical formulations with targeted skin delivery to enhance skin rejuvenation. Methods: Four multi-weight HA plus antioxidant complex-based formulations: 1) Multi-Weight HA plus Antioxidant Complex Lotion with SPF 30 (Day Lotion); 2) Multi-Weight HA plus Antioxidant Complex Cream (Night Cream); 3) Multi-Weight HA plus Antioxidant Complex Gel Cream; and 4) Multi-Weight HA plus Antioxidant Complex Boost Serum were clinically evaluated for key attributes including moisturization via corneometer, with clinical grading of: dryness, roughness, fine lines and wrinkles, and following daily use of the individual products for up to eight weeks. Results: Daily use of the multi-weight HA plus antioxidant complex-based formulations demonstrated significant improvements in all parameters evaluated compared to baselines, with changes in moisturization observed within 30 minutes of application, and changes in clinical grading parameters of dryness, roughness, fine lines and wrinkles observed as early as two weeks. Conclusion: These data demonstrate the clinical benefits of daily use of multi-weight HA plus antioxidant complex-based moisturizers for overall improvement in skin health and appearance.

Application habits and practices of regular sunscreen users in the United States: Results of an online survey.

A nationwide online survey assessed claimed usage of sunscreen products in 2283 self-identified regular sun protection factor (SPF) consumers (RSPFC) in the United States. Subjects applied sunscreen most frequently when spending more than 3 h in the sun. Sunscreen usage peaks during the summer, with sunny weather prompting 99% usage of beach/recreational SPF products but drops to approximately 50% and 30% on partly cloudy and cloudy days, respectively, regardless of SPF product category. About half of RSPFC augment sunscreen product usage by limiting time in the sun and wearing a hat. SPF products are not reapplied by approximately 20-60% of RSPFC, depending upon product category, and reapplication was less than 33% on cloudy and partly cloudy days. Primary reasons for reapplication were water exposure, number of hours in the sun, and being active/sweating, most notably for beach/recreational SPF products. Importantly, in children, 45% of parents reported "redness" as a signal for reapplying sunscreen product. Only 10% of respondents correctly identified sunscreen products as drugs. Based on these results, while sunscreens may share common ingredients and efficacy measures, their usage by consumers varies widely depending on product type, season, weather, gender, age, and geographical location.

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 aimed to compare the photoprotection of organic sunscreens enriched with antioxidant (AO) combinations against VL + UVA1 induced biologic effects. The efficacy was compared with 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 h 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.

OBJECTIF: les effets synergiques de la lumière visible (LV) et des rayons ultraviolets long (UVA1) (LV + UVA1, 370 à 700 nm) sur l'induction de la pigmentation et de l'érythème cutané ont été démontrés et liés à l'exacerbation des affections dermatologiques, notamment le mélasma et l'hyperpigmentation post-inflammatoire. Cette étude visait à comparer la photoprotection des écrans solaires organiques enrichis en associations antioxydantes (AO) contre les effets biologiques induits par LV+UVA1. L'efficacité a été comparée à celle offerte par un écran solaire teinté disponible dans le commerce. MÉTHODES: dix sujets adultes en bonne santé présentant des phototypes cutanés de Fitzpatrick IV à VI ont été inclus (neuf ont terminé l'étude). On a utilisé une dose LV+UVA1 de 380 J/cm2. Les méthodes d'évaluation étaient la photographie polarisée, le score global de l'investigateur et la spectroscopie de réflectance diffuse (DRS). Les mesures ont été obtenues immédiatement à l'entrée dans l'étude et, 24 h et 7 jours après l'irradiation. RÉSULTATS: les sites traités avec un produit de protection solaire teinté présentaient une pigmentation significativement inférieure à celle de la peau non traitée mais irradiée, à toutes les heures de mesure. Cependant, les résultats de la DRS ont démontré que l'écran solaire 5-AO fonctionnait de manière comparable ou mieux que tous les écrans solaires testés avec une dyschromie, un érythème retardé et une pigmentation relativement plus faible. CONCLUSION: ces résultats mettent en évidence le potentiel des écrans solaires enrichis en AO comme facteur de photoprotection contre LV+UVA1. La combinaison de l'efficacité et de l'aspect esthétique de ce produit peut permettre une plus grande acceptabilité, ce qui est essentiel compte tenu de la disponibilité limitée des moyens de protection contre cette gamme d'ondes.

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.

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.

Multi-laboratory study of hybrid diffuse reflectance spectroscopy to assess sunscreen SPF and UVA-PFs.

BACKGROUND: Proof-of-principle studies have established the use of Hybrid Diffuse Reflectance Spectroscopy (HDRS) methods to assess both Ultraviolet-A Protection Factor (UVA-PF) and Sun Protection Factor (SPF) indices in individual laboratories. METHODS: Multiple laboratories evaluated 23 emulsions and two spray sunscreen products to evaluate repeatability and accuracy of assessment of SPF and UVA-PF values, using HDRS test systems from various manufacturers using different designs. RESULTS: All of the laboratories reported similar SPF and UVA-PF values within a narrow range of values to establish the reliability of the HDRS methodology across laboratories, independent of equipment manufacturer or operator. CONCLUSION: HDRS test methodology provides a reliable objective instrumental estimation of sunscreen SPF and UVA-PF. These data were provided to ISO-TC217 WG7 to substantiate the ongoing development of an ISO Standard HDRS Method.

Evaluation of sunscreen efficacy over time and re-application using hybrid diffuse reflectance spectroscopy.

BACKGROUND: In 2007, the FDA added requirements for sunscreens to be labeled "re-apply at least every 2 hours" based on very limited data. This study used hybrid diffuse reflectance spectroscopy (HDRS) to evaluate the persistence of protection by 80 minutes water-resistant sunscreen formulation with and without re-application, and with and without sweat-inducing activity over 6 hours. METHODS: Sunscreens were applied to subject's foreheads and backs, and they remained at rest or exercised to induce sweating in a heated environment. Efficacy of a sun protection factor (SPF 50) very water-resistant sunscreen was measured with HDRS instrumentation and ultraviolet (UV) photography to determine the sunscreen protection over time. RESULTS: The sunscreen maintained SPF 50 efficacy over 6 hours for the non-active group with a single application, and for 2 hours for the active group, dropping slowly to SPF 30 level after 6 hours of sweating. Re-application of sunscreen gave additive SPF, with two applications resulting in SPF >100 and three applications approximately SPF 150. UV photography was insensitive to the differences in protection detected with HDRS instrumentation. CONCLUSIONS: Sunscreen efficacy is maintained over time in the absence of sweating or rub-off. After two hours of sweating, an 80 minutes water-resistant sunscreen does not need to be re-applied "at least every 2 hours."

Long-wavelength Ultraviolet A1 and Visible Light Photoprotection: A Multimodality Assessment of Dose and Response.

Human skin is exposed to visible light (VL; 400-700 nm) and long-wavelength ultraviolet A1 (UVA1) radiation (370-400 nm) after the application of organic broad-spectrum sunscreens. The biologic effects of these wavelengths have been demonstrated; however, a dose-response has not been investigated. Ten subjects with Fitzpatrick skin phototype IV-VI were enrolled. Subjects were irradiated with 2 light sources (80-480 J cm-2 ): one comprising VL with less than 0.5% UVA1 (VL+UVA1) and the other pure VL. Skin responses were evaluated for 2 weeks using clinical and spectroscopic assessments. 4-mm punch biopsies were obtained from nonirradiated skin and sites irradiated with 480 J cm-2 of VL+UVA1 and pure VL 24 h after irradiation. Clinical and spectroscopic assessments demonstrated a robust response at VL+UVA1 sites compared with pure VL. Histology findings demonstrated a statistically significant increase in the marker of inflammation (P < 0.05) and proliferation (P < 0.05) at the irradiated sites compared with nonirradiated control. Threshold doses of VL+UVA1 resulting in biologic responses were calculated. Results indicate that approximately 2 h of sun exposure, which equates to VL+UVA1 dose (~400 J cm-2 ), is capable of inducing inflammation, immediate erythema and delayed tanning. These findings reinforce the need of photoprotection beyond the UV range.

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

Solar radiation is known to be a major contributor to the development of skin cancer. Most sunscreen formulations, including those with broad spectrum, offer minimal protection in long-wavelength ultraviolet A1 (UVA1; 370-400 nm) and visible light (VL; 400-700 nm) domain. There is limited information regarding the impact of this broad waveband (VL + UVA1, 370-700 nm) on those with light skin. In this study, ten healthy adult subjects with Fitzpatrick skin phototypes I-III were enrolled. On day 0, subjects' lower back was exposed to a VL + UVA1 dose of 480 J cm-2 . A statistically significant increase in erythema immediately after irradiation compared with subjects' baseline nonirradiated skin was observed. Clinically perceptible erythema with VL + UVA1 is a novel finding since the erythemogenic spectrum of sunlight has primarily been attributed to ultraviolet B and short-wavelength ultraviolet A (320-340 nm). The results emphasize the need for protection against this part of the solar spectra and warrant further investigation.

UV fluorescence excitation spectroscopy as a noninvasive predictor of epidermal proliferation and clinical performance of cosmetic formulations.

BACKGROUND: The epidermis is the outermost layer of skin and is composed of cells primarily containing keratin. It consists of about ten layers of living cells (keratinocytes) and ten layers of dead cells (corneocytes). Thinning of the epidermis and decreased proliferation of its cells are associated with aging related changes in skin, including wrinkling and laxity. Fluorescence excitation spectroscopy is a noninvasive method of monitoring characteristic excitation-emission peaks in skin that have been related to the epidermal and dermal composition. The magnitude of the peak that occurs at 295nm excitation (F295) has been linked to changes in epidermal thickness, proliferation, and skin aging. AIM: The goal of this study is to correlate changes in the F295 signal with proliferation of cells and thickening of the epidermis induced by cosmetic formulations. We hypothesize that two commonly used cosmetic ingredients, retinol and glycolic acid, will increase these markers that have been implicated in skin anti-aging. METHODS: In a placebo-controlled study subjects' forearms were treated with formulations containing retinol or glycolic acid under occlusive patch for a period of 21 days. Skin fluorescence was measured at baseline and after treatment, and biopsies were taken following treatment for histological analysis of epidermal thickness and cell proliferation. RESULTS: After 21 days of treatment retinol and glycolic acid formulas significantly increased F295 (by 265.1±33.5% and 162.2±18.7% respectively), whereas the placebo control formula did not induce a change from baseline. Furthermore, retinol and glycolic acid treatments significantly increased epidermal thickness (by 63.1% and 7.8% respectively) and keratinocyte proliferation (by 236.9% and 62.8% respectively) versus placebo control. CONCLUSION: Increases in F295 were found to correlate with epidermal renewal, but more so with increased cell proliferation than epidermal thickness. We conclude that the F295 signal is a fast and reliable early indicator of epidermal remodeling in skin that can be used to distinguish between formulations with different cosmetic ingredients.

Photoprotection against visible light-induced pigmentation.

OBJECTIVE: This paper presents in vivo an in vitro studies demonstrating the induction of pigmentation in human skin by visible light which can be blocked by using formulation containing the correct amount of yellow iron oxide (YIO). METHODS: An in vitro absorption method was developed to determine the protection provided by a test formulation containing 4.5% YIO using an IPD UVA-VIS action spectrum. Following the development of the in vitro method and in vivo study with 10 normal healthy volunteers with Fitzpatrick skin phototypes IV to VI was conducted to verify if the predictive model. RESULTS: The in vitro model for visible light protection provided a protection factor of 2.5 using the in vitro absorption spectrum of 4.5% of YIO with a very similar result from the in vivo study with a protection factor of 3.0. Multiple daily exposures of visible light have shown increase in skin pigmentation and the application of YIO provide less development of pigmentation when compared to unprotected skin. CONCLUSION: In vitro testing of the absorbance of the pigmented formulation using a proposed action spectrum for immediate pigment darkening (IPD) response in the visible light range supports the in vivo protection observations for persistent pigment darkening (PPD) and can be used as predictor for skin pigmentation induced by visible light.

The Kollias legacy: Skin autofluorescence and beyond.

In a paper published at the J Invest Dermatol in 1998 Nik Kollias and coworkers described distinct changes in skin native fluorescence associated with skin aging and photoaging, using in vivo fluorescence excitation spectroscopy. The assignment of the 295 nm band to tryptophan fluorescence had a profound significance influencing many later studies from multiple groups. The reproducible changes in skin native fluorescence suggested that aging causes predictable alterations in both the epidermis and the dermis, whereas chronic UV exposure induces the appearance of new fluorophores. This seminal, but insufficiently widely appreciated work deserves re-examination as it points to important horizons in future experimental dermatology, such as cancer diagnostics, diabetes, wound healing, and understanding skin aging and photoaging mechanisms.

Water-Holding and Transport Properties of Skin Stratum Corneum of Infants and Toddlers Are Different from Those of Adults: Studies in Three Geographical Regions and Four Ethnic Groups.

BACKGROUND/OBJECTIVE: Epidermal structure, function, and composition are different in white infants and adults. We investigated whether ethnicity and location contribute to differences in functional and clinical measurements of skin barrier function during the first years of life and in adults. METHODS: Children (n = 397, ages 3-49 mos) and women (n = 117, mean age 31 yrs) were enrolled at independent centers in Beijing, China (ethnic Chinese), Skillman, New Jersey (white, African American), and Mumbai, India (ethnic South Asian). Water barrier properties of the stratum corneum were assessed using high-frequency conductance and transepidermal water loss (TEWL) on the dorsal forearm and upper inner arm. Digital imaging was used to evaluate facial erythema and scaling. RESULTS: Despite differences in local climate, TEWL was similar in adults. In children, conductance and TEWL decreased monotonically from age 3 months to 4 years. In children from Beijing, TEWL values were higher in both arm locations than in children in Mumbai and Skillman. No significant differences were observed in TEWL or conductance between the white and African American groups. CONCLUSION: In general, TEWL and conductance were greater on the upper inner arm than the dorsal forearm. Erythema and scaling were observed most often in subjects from Beijing and most infrequently in subjects from Mumbai. Stratum corneum water barrier properties were different in children and adults. Although there may be differences in these properties between ethnic groups in childhood, TEWL values were similar in adults across the three geographic locations and four ethnicities.

Visible Light Induces Melanogenesis in Human Skin through a Photoadaptive Response.

Visible light (400-700 nm) lies outside of the spectral range of what photobiologists define as deleterious radiation and as a result few studies have studied the effects of visible light range of wavelengths on skin. This oversight is important considering that during outdoors activities skin is exposed to the full solar spectrum, including visible light, and to multiple exposures at different times and doses. Although the contribution of the UV component of sunlight to skin damage has been established, few studies have examined the effects of non-UV solar radiation on skin physiology in terms of inflammation, and limited information is available regarding the role of visible light on pigmentation. The purpose of this study was to determine the effect of visible light on the pro-pigmentation pathways and melanin formation in skin. Exposure to visible light in ex-vivo and clinical studies demonstrated an induction of pigmentation in skin by visible light. Results showed that a single exposure to visible light induced very little pigmentation whereas multiple exposures with visible light resulted in darker and sustained pigmentation. These findings have potential implications on the management of photo-aggravated pigmentary disorders, the proper use of sunscreens, and the treatment of depigmented lesions.

Evaluation of Seasonal Changes in Facial Skin With and Without Acne.

The objective of this study was to compare facial skin of adolescent males with (acne) and without acne (non-acne) over the course of 1 year. At study entry, presence of acne was determined by clinical image analysis (acne n=7, non-acne n=10). Monthly evaluations of skin condition were made using standard and fluorescent imaging, fluorescence spectroscopic analysis, sebum analysis, skin high frequency conductivity (moisture content), transepidermal water loss (TEWL), and sampling of skin bacteria (aerobic and anaerobic). Data were evaluated seasonally. Over the course of the study, subjects in the acne and non-acne groups had no significant increase in their clinical acne score. Sebum production was significantly greater in subjects with acne than in those without for each season examined (P<0.019) and was lowest in the winter and highest in the fall. TEWL was higher in those with acne than without acne across all seasons (P=0.001). Skin moisture in both groups was increased during summer and fall compared with winter (P≤0.016 for both seasons). Subjects with acne had a higher recovery of both aerobic and anaerobic bacteria compared with subjects without acne (P≤0.015). Analysis of cheek skin in the nasal area revealed significantly higher fluorescence (500-800 nm) in image-based and spectroscopic analysis from subjects with acne, suggesting the greater presence of the bacterial metabolite porphyrin in those with acne. In these cohorts of adolescent males, significant differences in sebum production, skin barrier function, moisture content, and microbial load (anaerobic and aerobic) were noted between those with and without acne. Evidence for seasonality was observed, with lower lipid production and reduced barrier function during the winter. More studies to quantify differences in skin lipid components and bacterial species among these cohorts are planned.

IL-11, IL-1α, IL-6, and TNF-α are induced by solar radiation in vitro and may be involved in facial subcutaneous fat loss in vivo.

BACKGROUND: The loss of subcutaneous (sc) fat is associated with aging. Inflammatory cytokines, such as interleukin-1 α (IL-1α), interleukin-11 (IL-11) and tumor necrosis factor-α (TNF-α), are known to inhibit the differentiation of preadipocytes. OBJECTIVE: This study investigated the potential role of inflammatory cytokines in solar-radiation-induced facial fat loss. METHODS: Cultured fibroblasts, keratinocytes, and skin equivalents were exposed to various doses of radiation from a solar simulator. Inflammatory cytokines' mRNA production and protein secretion were examined by qRT-PCR and ELISA, respectively. In some experiments, epidermal-dermal equivalents were pretreated topically with a broad-spectrum sunscreen prior to solar simulated radiation (SSR). Human facial preadipocytes treated with recombinant IL-11 or with conditioned media from solar-irradiated equivalents were evaluated for the level of adipocyte differentiation by image analyses, Oil red O staining, and the expression of adipocyte differentiation markers. RESULTS: IL-11, IL-1α, IL-6, and TNF-α protein secretion were induced from epidermal-dermal equivalents by exposure to SSR. A sunscreen prevented SSR-induced inflammatory cytokines production from such equivalents. Exposure of facial preadipocytes to conditioned medium from solar-irradiated epidermal-dermal equivalents inhibited their differentiation into mature adipocytes. Consequently, conditioned medium from sunscreen-pretreated, solar-irradiated equivalents did not inhibit differentiation of preadipocytes. A cocktail of neutralizing antibodies to IL-11, IL-1α, IL-6 and TNF-α significantly reduced the SSR-induced inhibition of preadipocyte differentiation. CONCLUSION: These results support the hypothesis that SSR-induced inflammatory cytokine may be involved in the photoaging-induced loss of facial subcutaneous fat. Inhibition of this process, e.g. by sunscreens, might slow or prevent photoaging-induced changes in facial contouring.

Irradiation of skin with visible light induces reactive oxygen species and matrix-degrading enzymes.

Daily skin exposure to solar radiation causes cells to produce reactive oxygen species (ROS), which are a primary factor in skin damage. Although the contribution of the UV component to skin damage has been established, few studies have examined the effects of non-UV solar radiation on skin physiology. Solar radiation comprises <10% of UV, and thus the purpose of this study was to examine the physiological response of skin to visible light (400-700 nm). Irradiation of human skin equivalents with visible light induced production of ROS, proinflammatory cytokines, and matrix metalloproteinase (MMP)-1 expression. Commercially available sunscreens were found to have minimal effects on reducing visible light-induced ROS, suggesting that UVA/UVB sunscreens do not protect the skin from visible light-induced responses. Using clinical models to assess the generation of free radicals from oxidative stress, higher levels of free radical activity were found after visible light exposure. Pretreatment with a photostable UVA/UVB sunscreen containing an antioxidant combination significantly reduced the production of ROS, cytokines, and MMP expression in vitro, and decreased oxidative stress in human subjects after visible light irradiation. Taken together, these findings suggest that other portions of the solar spectrum aside from UV, particularly visible light, may also contribute to signs of premature photoaging in skin.

The value of the ratio of UVA to UVB in sunlight.

The objective of this communication is to present the calculated ratio between UVA and UVB irradiance from sunrise to sunset and under a number of weather conditions. UVA plays an important role in the sun spectrum and a lot of attention has been paid lately regarding the protection of people from UVA. Solar spectra were collected in Kuwait City located at 29.3° North latitude (similar to that of Houston, TX) over a period of 8 months and under various weather conditions. Spectra were collected from 260 nm to 400 nm in 2 nm increments for solar elevation angles from 10° to 90° using a calibrated Optronics Laboratories OL-742 Spectroradiometer. The measurements reported in this study the ratio of UVA (320-400 nm) to UVB (280-320 nm) in solar terrestrial radiation remains essentially constant and equal to 20 for the part of the day when the solar elevation is greater than 60°. Consequently the value of the ratio of solar UVA/UVB should be considered as equal to 20 for studies in photobiology and photomedicine. When the wavelength limiting the range of UVA and UVB is 315 nm (i.e. UVB: 280-315 nm and UVA: 315-400 nm) the ratio of UVA to UVB becomes equal to 41.

Impact of long-wavelength UVA and visible light on melanocompetent skin.

The purpose of this study was to determine the effect of visible light on the immediate pigmentation and delayed tanning of melanocompetent skin; the results were compared with those induced by long-wavelength UVA (UVA1). Two electromagnetic radiation sources were used to irradiate the lower back of 20 volunteers with skin types IV-VI: UVA1 (340-400 nm) and visible light (400-700 nm). Pigmentation was assessed by visual examination, digital photography with a cross-polarized filter, and diffused reflectance spectroscopy at 7 time points over a 2-week period. Confocal microscopy and skin biopsies for histopathological examination using different stains were carried out. Irradiation was also carried out on skin type II. Results showed that although both UVA1 and visible light can induce pigmentation in skin types IV-VI, pigmentation induced by visible light was darker and more sustained. No pigmentation was observed in skin type II. The quality and quantity of pigment induced by visible light and UVA1 were different. These findings have potential implications on the management of photoaggravated pigmentary disorders, the proper use of sunscreens, and the treatment of depigmented lesions.