UVB Protection Research Articles

Prevention of skin damage to solar radiation in elderly patients: sunscreens

Exposure to UV radiation can cause skin damage; among UV rays UVB are commonly considered to be more important in inducing photoaging and skin cancer; however in recent years some authors have claimed an important role also for UVA that can concur with UVB to damage the skin. UVB rays have a wavelength between 280 and 320 nm and are responsible for immediate skin damage represented by erythema. On the contrary, the skin damage produced by UVA, with a longer wavelength than UVB comprised between 320 and 400nm, is generally not clinically evident but will accumulate over the years, showing its effects later. In the past the attention of the formulation of sunscreens was placed on UVB protection, but nowadays, as we have mentioned before, UVA protection is also necessary. Moreover, UVA radiation is not shielded either by plastic or glass, so the skin can be exposed even in apparently protected closed spaces, such as the home or car. Therefore there are now filters or sunscreens available with complex formulas that effectively protect both from UVB and UVA The physical filters, also called sunblocks, made of metals such as zinc oxide or titanium dioxide, offer excellent protection, but they do take on a bleached unpleasant side effect. Some researchers have developed formulas with micronized particles to reduce this effect but the results are not always very satisfactory. On the other hand, the chemical filters are substances capable of using the energy of UV radiation to change their molecular structure. A possible solution has been found mixing physical and chemical sunscreens to obtain a higher sun protection factor (SPF) with reduced bleaching effect. However sunscreens must be used to protect the skin from excessive UV radiation, not to permit more UV exposure. Therefore we must not neglect the traditional precautions of wearing hats or protective clothing and avoiding the sun during the middle of the day.

Photostabilization Effect of Quercetin on the UV Filter Combination, Butyl Methoxydibenzoylmethane–Octyl Methoxycinnamate

The aim of the study was to investigate the effect of the natural antioxidant quercetin on the photostability of the most widely used combination of UVA (320-400 nm) and UVB (290-320 nm) filters, respectively butyl methoxydibenzoylmethane (BMDBM) and octyl methoxycinnamate (OMC). In order to reproduce the conditions prevalent in commercial sunscreen products, the stabilizing efficacy of quercetin was evaluated in model creams containing BMDBM (3%, wt/wt) together with OMC (4%, wt/wt) and exposed to a solar simulator at an irradiance corresponding to natural sunlight. Quercetin was found to enhance the photostability of the two UV filters in a concentration-dependent way. Addition of quercetin to the sunscreen formulation significantly reduced the photodegradation of BMDBM and OMC from 40.3 +/- 2.4 to 27.7 +/- 2.6% and from 51.3 +/- 2.1 to 42.2 +/- 2.0%, respectively. Moreover, comparative photodegradation studies demonstrated that quercetin was much more effective and at a lower concentration than commonly used stabilizer (octocrylene) and antioxidants (vitamin E, butylated hydroxyanisole). In vitro determination of the UVB and UVA protection parameters showed that the quercetin-based formulation fulfilled the official requirements on sunscreen products. Because of its photostabilizing and multiple antioxidant properties, quercetin represents a useful additive for the formulation of effective broad-spectrum sunscreens containing BMDBM and OMC.

Comparaison in vitro de l’efficacité et de la photostabilité de trois crèmes antisolaires

While sun products are considered as cosmetics within the European Union, in the United States and Japan they are considered as medicines. Following the European market launch of the first sun product considered as a class-1 medical device, Daylong actinica, we compared products having different types of status. Three sun products underwent in vitro testing in order to determine their efficacy in terms of UVB and UVA protection, as well as their photostability. We used a classic cosmetic product (Nivea Sun 50+), a product displaying particular claims in terms of duration of efficacy (Dix20), and a medical device (Daylong actinica). The in vitro method used involves measuring the transmittance of a sample of the product applied to a polymethylmethacrylate plate using an integrating sphere spectrophotometer. In terms of efficacy, the three products tested were compliant with the European recommendations concerning sun products. In view of the results, the labelling for Nivea Sun 50+ and Daylong actinica) can both display the wording "50+". However, their photostability was poor under our experimental conditions. For Dix20), the labelling that may be displayed is 50. This value gradually decreases to 20 after 10hours of irradiation, accounting for the displayed claim. It is somewhat difficult to understand the coexistence on the market of products having different types of status without any prior establishment of clear limits in terms of indices, for example.

Cloning and characterization of a UV-B-inducible maize flavonol synthase

Flavonols are important compounds for conditional male fertility in maize (Zea mays) and other crops, and they also contribute to protecting plants from UV-B radiation. However, little continues to be known on how maize and other grasses synthesize flavonols, and how flavonol biosynthesis is regulated. By homology with an Arabidopsis flavonol synthase (AtFLS1), we cloned a maize gene encoding a protein (ZmFLS1) capable of converting the dihydrokaempferol (DHK) and dihydroquercetin (DHQ) dihydroflavonols to the corresponding flavonols, kaempferol (K) and quercetin (Q). Moreover, ZmFLS1 partially complements the flavonol deficiency of the Arabidopsis fls1 mutant, and restores anthocyanin accumulation to normal levels. We demonstrate that ZmFLS1 is under the control of the anthocyanin (C1/PL1 + R/B) and 3-deoxy flavonoid (P1) transcriptional regulators. Indeed, using chromatin immunoprecipitation (ChIP) experiments, we establish that ZmFLS1 is an immediate direct target of the P1 and C1/R regulatory complexes, revealing similar control as for earlier steps in the maize flavonoid pathway. Highlighting the importance of flavonols in UV-B protection, we also show that ZmFLS1 is induced in maize seedlings by UV-B, and that this induction is in part mediated by the increased expression of the P1, B and PL1 regulators. Together, our results identify a key flavonoid biosynthetic enzyme so far missed in maize and other monocots, and illustrate mechanisms by which flavonol accumulation is controlled in maize.

The ARABIDOPSIS Accession Pna-10 Is a Naturally Occurring sng1 Deletion Mutant

Sinapoylmalate is the major sinapate ester found in leaves of Arabidopsis thaliana, where it plays an important role in UV-B protection. Metabolic profiling of rosette leaves from 96 Arabidopsis accessions revealed that the Pna-10 accession accumulates sinapoylglucose instead of sinapoylmalate. This unique leaf sinapate ester profile is similar to that of the previously characterized sinapoylglucose accumulator1 (sng1) mutants. SNG1 encodes sinapoylglucose:malate sinapoyltransferase (SMT), a serine carboxypeptidase-like (SCPL) enzyme that catalyzes the conversion of sinapoylglucose to sinapoylmalate. In the reference Columbia genome, the SNG1 gene is located in a cluster of five SCPL genes on Chromosome II. PCR and sequencing analysis of the same genomic region in the Pna-10 accession revealed a 13-kb deletion that eliminates the SNG1 gene (At2g22990) and the gene encoding sinapoylglucose:anthocyanin sinapoyltransferase (SAT) (At2g23000). In addition to its sinapoylmalate-deficient phenotype, and consistent with the loss of SAT, Pna-10 is unable to accumulate sinapoylated anthocyanins. Interestingly, the Pna-17 accession, collected from the same location as Pna-10, has no such deletion. Further analysis of 135 lines collected from the same location as Pna-10 and Pna-17 revealed that four more lines contain the deletion found in Pna-10 accession, suggesting that either the deletion found in Pna-10 is a recent event that has not yet been eliminated through selection or that sinapoylmalate is dispensable for the growth of Arabidopsis under field conditions.

Ultraviolet irradiation induced oxidative stress and response of antioxidant system in an intertidal macroalgae Corallina officinalis L.

The response of the antioxidant defense system of an intertidal macroalgae Corallina officinalis L. to different dosages of UV-B irradiation was investigated. Results showed that superoxide dimutase (SOD) and peroxidase (POX) increased and then maintained at a relatively stable level when subjected to UV-B irradiation. Catalase (CAT) activity under medium dosage of UV-B irradiation (Muv) and high dosage of UV-B irradiation (Huv) treatments were significantly decreased. Ascorbate peroxidase (APX) activity first remained unaltered and then increased in Huv treatment. In addition, the assay on isozymes was carried out using non-denaturing polyacrylamide gel electrophoresis (PAGE). The activities of some SOD isoforms were altered by UV-B. Two new bands (POX V and POX VII) appeared upon exposure to all three UV-B dosages. CAT III activity was increased by low dosage of UV-B irradiation (Luv), whereas CAT III and CAT IV disappeared when the alga was exposed to Muv and Huv. Two bands of APX (APX VI and APX VII) were increased and a new band (APX X) was observed under Huv exposure. H 2O 2 and thiobarbituric acid reacting substance (TBARS) increased under Muv and Huv treatments. Overall, UV-B protection mechanisms are partly inducible and to a certain extent sufficient to prevent the accumulation of damage in C. officinalis.

In vitro and in vivo anti-photoaging effects of an isoflavone extract from soybean cake

Ethnopharmacological relevance Soy has been used in traditional Chinese medicine for thousands of years for its health and nutritional benefits, as well as to treat and care for the skin. Advanced skin care research has shown that soy isoflavone and genistein are effective in reducing damage to the skin from the sun. Aim of the study To study the protective effects of isoflavone extract from soybean cake against the UVB-induced skin damage. Materials and methods The in vitro effects and possible mechanisms of soybean extract on UVB protection were determined in HaCaT cells. In the in vivo study, ICR-Foxn/ nu mice were irradiated with UVB. The epidermal thickness, catalase and the expressions of cyclooxygenase-2 (COX-2) and proliferating cell nuclear antigen (PCNA) were detected to evaluate the antioxidant and anti-inflammatory activities of the isoflavone extract. Results Our in vitro studies showed that UVB-induced HaCaT cell death and the phosphorylation of p38, JNK, and ERK1/2 decreased in the presence of isoflavone extract. In the in vivo studies, we found that the topical application of isoflavone extract before UVB irritation decreased the epidermal thickness and the expressions of COX-2 and PCNA and increased catalase concentration. These results showed anti-photoaging effect of isoflavone extract from soybean cake involved the inhibition of UVB-induced apoptosis and inflammation. Conclusions It is shown that isoflavone extract from soybean cake may be functional cosmeceutical candidate for skin photoaging.

Effect of phlorotannins isolated from Ecklonia cava on melanogenesis and their protective effect against photo-oxidative stress induced by UV-B radiation

In the present study, three kinds of phlorotannins, marine algal polyphenol, were isolated from a brown alga Ecklonia cava, and their inhibitory effect on melanogenesis as well as the protective effect against photo-oxidative stress induced by UV-B radiation was investigated. The effect on melanogenesis was evaluated via the inhibitory effects of tyrosinase and melanin synthesis. Among the phlorotannins, dieckol showed higher effect than that of the other phlorotannins in the both assays; especially the value of dieckol in the tyrosinase inhibition assay was relatively higher than that of a commercial tyrosinase inhibitor (kojic acid). The UV-B protection effect was evaluated via DCFH-DA, MTT, comet assays, and morphological changes in fibroblast. Intracellular ROS induced by UV-B radiation was reduced by the addition of phlorotannins and cell viability was dose-dependently increased. Moreover, dieckol demonstrated strong protective properties against UV-B radiation-induced DNA damage via damaged tail intensity and morphological changes in fibroblast. Hence, these results indicated that dieckol isolated from E. cava has potential whitening effects and prominent protective effects on UV-B radiation-induced cell damages, which might be used in pharmaceutical and cosmeceutical industries.

Photoprotective role of carotenoids in yeasts: Response to UV-B of pigmented and naturally-occurring albino strains

In this work, the photoprotective role of carotenoids in yeasts was analysed by contrasting the responses to UV-B of pigmented and naturally occurring albino strains of Sporobolomyces ruberrimus and Cystofilobasidium capitatum in different conditions. Albino and pigmented strains were confirmed to be conspecific by PCR fingerprinting and rDNA sequencing. Experimental exposure to UV-B conducted with both yeast species showed that the pigmented strains were more tolerant to UV-B than the albino strains and that the increment in carotenoid contents during the stationary growth phase enhance survivorship. These results indicated that carotenoid pigments afford UV-B protection in yeasts.

Interference by baicalin in the formation of photoproduct in epidermal cells from BALB/c mice irradiated with ultraviolet B.

Objective To investigate the formation and elimination of photoproduct in epidermal cells from BALB/c mice irradiated with ultroviolet B, and to observe the interference by baicalin in it. Methods BALB/c mice were randomized into 6 groups, I.e., blank control group receiving no exposure or protection, baicalin group receiving protection with baicalin, acetone group receiving acetone pretreatment, UVB group receiving UVB irradiation but no protection, UVB + baicalin group receiving UVB irradiation and protection with baicalin, UVB + acetone group receiving acetone pretreatment and UVB irradiation. Baicalin was applied at 1 mg/cm2 on the back of mice for 3 days in baicalin group and UVB + baicalin group. Twenty hours after the last application, UVB irradiation of 180 mJ/cm2 was given to mice in UVB group and UVB + baicalin group. Skin specimens were obtained from the tested sites at 1, 24, and 48 hours, respectively, after the irradiation. Cyclobutane pyrimidine dimers (CPD) was detected in the specimens with immunohistochemical staining and Southwestern dot blotting. Results CPD was observed only in irradiated mice. The relative content of CPD in epidermal cells 1, 24 and 48 hours after the irradiation was (100±5.22)%, (75.34±8.22)% and (42.11±3.24)%, respectively, in UVB group, (81.45±5.22)%, (32.14±6.33)% and ( 5.21±3.15 )% respectively, in UVB+baicalin group, ( 106±8.21 )%, (70.23±4.13 )% and (41.22±4.21)%, respectively, in UVB + acetone group. A significant difference was observed in the relative content of CPD between UVB group and UVB + baicalin group at 1, 24 and 48 hours after the irradiation (P<0.05, 0.01, 0.01, respectively). Conclusions Taken together, these results suggest that topical baicalin application mitigates DNA photo-damage. Baicalin is therefore a promising protective substance against UVB radiation. Key words: Baicalin; Pyrimidine dimers; Ultraviolet rays

Proposal of UV-A Protection Efficiency (APE) for Fabrics using in vitro DNA Strand-breaking Activity

We propose UV-A Protection Efficiency (APE) as a new valuable index of UV-A protection provided by fabrics, in addition to a UV-B protection factor UPF (Ultraviolet Protection Factor) recommended by CIE. APE was estimated by determining efficiency of apparel white fabrics in suppressing the formation of strand-breakage in plasmid DNA by sparfloxacin-photosensitization with a black light blue (BLB) lamp and solar UV-A radiation. The lower UV-A transmittance of fabrics showed the higher APE. The close inverse correlation between APE and the transmittance of fabrics at 360 nm was demonstrated with the correlation coefficient of −0.86. These findings support the validity of APE as a useful index of UV-A protection by fabrics. For practical use, APE is ranked to three grades depending on tolerated exposure time: APE from 3.5 to 4.5 is good protection, APE from 4.5 to 5.5 is very good protection, APE more than 5.5 is excellent protection. Present study also states that both APE and UPF are the important factors for protecting the ultraviolet radiation by fabrics.

The Effects of Dyeing on UV Protection Efficiency of Apparel Fabrics

The ultraviolet radiation (UV) protection efficiency of apparel dyed fabrics of cotton and polyester were evaluated by UPF (UV-B protection index) and APE (UV-A protection index) to investigate the effects of hue and lightness of the fabrics. UV transmittance of fabrics changed along with the thickness of the fabrics. The characteristic spectral transmittance of dyes appeared on the dyed taffeta (thickness: 0.1 mm), but on the dyed fabrics thicker than kanakin (thickness: 0.3 mm) they were less than 10% in all UV region. White fabrics having not enough UV protection efficiency increased their UPF and APE by dyeing and showed good protection efficiency. If the L* values of dyed fabrics were same, UPF is higher in the order of yellow, red, blue and black color. The required conditions for taffeta, thinnest fabric in this research to have enough UV protection efficiency are as follows: L* values of cellulose should be less than 25 regardless of their hue, L* values of polyester should be less than 86 in yellow, less than 67 in red and blue, less than 60 in black color, and addition to those transmittance at 370 nm should be less than 10%.

A novel skin depigmenting agent from Erigeron breviscapus and its mechanisms

In the present study, three kinds of phlorotannins, marine algal polyphenol, were isolated from a brown alga Ecklonia cava, and their inhibitory effect on melanogenesis as well as the protective effect against photo-oxidative stress induced by UV-B radiation was investigated. The effect on melanogenesis was evaluated via the inhibitory effects of tyrosinase and melanin synthesis. Among the phlorotannins, dieckol showed higher effect than that of the other phlorotannins in the both assays; especially the value of dieckol in the tyrosinase inhibition assay was relatively higher than that of a commercial tyrosinase inhibitor (kojic acid). The UV-B protection effect was evaluated via DCFH-DA, MTT, comet assays, and morphological changes in fibroblast. Intracellular ROS induced by UV-B radiation was reduced by the addition of phlorotannins and cell viability was dose-dependently increased. Moreover, dieckol demonstrated strong protective properties against UV-B radiation-induced DNA damage via damaged tail intensity and morphological changes in fibroblast. Hence, these results indicated that dieckol isolated from E. cava has potential whitening effects and prominent protective effects on UV-B radiation-induced cell damages, which might be used in pharmaceutical and cosmeceutical industries.

Effect of resveratrol incorporated in liposomes on proliferation and UV-B protection of cells

The possibility of improving the efficacy of resveratrol, a polyphenol with strong antioxidant and free-radical scavenging properties, on cell proliferation and photoprotection by liposomal incorporation was investigated. Oligolamellar vesicles of different lipid compositions, loaded with resveratrol, were prepared and characterized by evaluating size, zeta potential, incorporation efficiency, electron microscopy and stability over 60 days. The effect of free and liposomal resveratrol on the viability of HEK 293 cells and their photoprotection after UV-B irradiation was assessed by the MTS method. Resveratrol decreased the cell viability at 100 μM concentration, while at 10 μM increased cell proliferation and also achieved the most effective photoprotection. Photomicrographs of the treated cells from inverted light and fluorescence microscopy demonstrated resveratrol effectiveness at 10 μM, as well as its toxicity at higher concentrations, based on changes in cell shape, detachment and apoptotic features. Interestingly, liposomes prevented the cytotoxicity of resveratrol at high concentrations, even at 100 μM, avoiding its immediate and massive intracellular distribution, and increased the ability of resveratrol to stimulate the proliferation of the cells and their ability to survive under stress conditions caused by UV-B light.

Commentary on ‘UVB‐SPF’: the SPF labels of sunscreen products convey more than just UVB protection

The FDA recently published a proposed amendment of the Final Monograph for OTC Sunscreen Products. Among the proposals, FDA revised solar simulator performance specifications and additional labeling for sunscreen products. The maximum allowable labeled sun protection factor (SPF) was increased to SPF 50 while simultaneously requiring it to be called 'UVB-SPF'. UVB accounts for 80-91% of the erythemic effectiveness of the UV solar simulator specified in the amendment. Analysis of the specified solar simulator spectrum used to determine SPF indicates that if 100% of the UVB is blocked, it is mathematically impossible to achieve an SPF in excess of approximately 11 without also blocking at least some UVA. Consequently significant UVA protection must be provided for sunscreen products to achieve SPFs of 15 and higher. At the maximum allowed SPF 50, where only 2% or less of the effective UV risk remains, the minimum reduction of UVA erythemal effectiveness must by definition be 78-90%. While mandating UVA protection criteria is doubtless important, especially as it relates to sunscreen photostability, there is no utility in, or basis for, the proposed 'UVB-SPF' descriptor as existing high SPF labeling indicates both UVB and UVA protection.

Transmittance characteristics of ultraviolet and blue-light-filtering intraocular lenses

To record the spectral transmittance curves of various ultraviolet (UV) and blue-light-filtering intraocular lenses (IOLs), evaluate their UV and blue-light-radiation- absorption capacities, and compare them with those of the natural crystalline lens. Department of Ophthalmology, Duisburg-Essen University, Essen, Germany. Eight IOLs from 6 manufacturers were evaluated. The transmittance of wavelengths from 200 nm to 800 nm was measured using a high-performance spectrophotometer with a diffuse transmittance accessory through a 1.5 mm aperture. All assessed IOLs provided good UVC (200 to 280 nm) and UVB (280 to 320 nm) protection, but 2 IOLs lacked sufficient UVA (320 to 400 nm) protection. Major differences in the absorption capacities were observed in the blue-light range (400 to 500 nm). The absorption characteristics of some UV and blue-light-filtering IOLs resembled those of the crystalline lens, but some differed. Long-term clinical trials should be performed to determine how blue-blocking IOLs affect the risk for progression of age-related macular degeneration.

Solar Protection — Effect of Selected Fabric and Use Characteristics on Ultraviolet Transmission

Clothing is worn in single- and multiple-layer arrangements and during use subjected to conditions such as extension and wetting. This study investigated how selected variables affected transmission of ultraviolet radiation (UVR) through fabrics and whether these variables interacted to modify transmission. Using a spectrophotometer the effect of i) fabric type (two knitted, two woven), color (black and white), wetness (dry, damp, wet), and extension (relaxed, extended (10 × 10%, 10 × 20%)), and ii) fabric type and layering (1, 2, 3 layers) of white fabrics, on UVR (290—400 nm), UVA (315—400 nm), UVB (290—315 nm), and ultraviolet protection factor (UPF) rating was investigated. Differences among variables were identified using univariate and repeated measures ANOVA, and interactions among variables identified and described. Selecting dark colors, limiting extension and layering fabric were shown to be effective ways of increasing UV protection and UPF by decreasing transmittance. However, the effect of color, extension and layering varied among fabric types and modified UVA and UVB transmittance differently.

Effect of Materials and Weaving Properties on UV Protection Efficiency of Apparel White Fabrics - Evaluation by Transmittance, Reflectance, Porosity and UPF -

The ultraviolet radiation (UV) protection efficiency of apparel white fabrics of cotton, nylon and polyester was investigated. The UV protection efficiency depended significantly on the transmittance of their polymer materials. For the cotton and polyester fabrics, the estimated UV protection efficiency showed a strong dependence on the weaving properties such as the type of weave, density of warp and weft, thickness, weight, fabric porosity and surface characteristics. Moreover, ultraviolet protection factor (UPF) of the white fabrics was evaluated for the UV-A and UV-B radiation. The results are summarized as follows: 1) The UV transmittance in the 250-400nm regions of white fabrics of cotton, nylon and polyester depends on that of their material polymers. 2) Polyester is defined as UV-B protective material, because it does not transmit wavelengths shorter than 310nm, and also the reflectance of polyester is lower than that of cotton and nylon in this wavelength regions. 3) The UV protection efficiency of white fabrics of cotton and polyester depends on their weaving properties, especially the type of weave such as plain and twill. 4) Polyester white fabrics with lower porosity than 5% have the higher UPF than 20. 5) The UPF is defined as a UV-B protection factor.

SAD2, an Importin β-Like Protein, Is Required for UV-B Response in Arabidopsis by Mediating MYB4 Nuclear Trafficking

We report that the Arabidopsis thaliana mutant sensitive to ABA and drought2 (sad2), which harbors a T-DNA insertion in an importin beta-like gene, is more tolerant to UV-B radiation than the wild type. Analysis of cyclobutane pyrimidine dimer accumulation revealed that less DNA damage occurred in sad2 than in the wild type during UV-B treatment. No significant growth difference was observed between sad2 and the wild type when treated with the genotoxic drug methyl methanesulfonate, suggesting that SAD2 functions in UV-B protection rather than in DNA damage repair. Whereas the R2R3-type transcription repressor MYB4 has previously been shown to negatively regulate the transcription of cinnamate 4-hydroxylase (C4H) and thus to regulate the synthesis of sinapate esters, expression of both MYB4 and C4H and accumulation of UV-absorbing compounds were significantly higher in sad2 than in the wild type. MYB4 did not localize to the nucleus in the sad2 mutant, suggesting that SAD2 is required for MYB4 nuclear trafficking. SAD2 and MYB4 coimmunoprecipitated, indicating that these proteins localize in the same complex in vivo. MYB4 protein specifically bound to its own promoter in gel shift assays and repressed its own expression, demonstrating that MYB4 protein and mRNA are part of a negative autoregulatory loop. This feedback loop is altered in the sad2 mutant due to the absence of MYB4 protein in the nucleus, leading to the constitutive expression of MYB4 and C4H and resulting in accumulation of UV-absorbing pigments that shield the plant from UV-B radiation.

Determination of Wavelength‐Specific UV Protection Factors of Sunscreens in Intact Skin by EPR Measurement of UV‐Induced Reactive Melanin Radical

There remains an unmet need for skin tissue-based assays for the measurement of the UVA protection and efficacy of sunscreens. Here we describe development of a novel electron paramagnetic resonance assay that uses the photogeneration of reactive melanin radical as a measure of UV light penetration to melanocytes in situ in skin. We have used areas of focal melanocytic hyperplasia in the skin of Monodelphis domestica to model the human nevus. We show that we are able to use this assay to determine the monochromatic protection factors (mPF) of research and commercial sunscreens at specific narrow wavebands of UVB, UVA and blue visible light. Both commercial sunscreens, a sun protection factor (SPF) 4 and an SPF 30 product, had mPFs in the UVB range that correlated well with their claimed SPF. However, their mPF in the UVA ranges were only about one-third of claimed SPF. This technique can be used to design and assay sunscreens with optimally balanced UVA and UVB protection.