Sunscreen Application Research Articles

Skin Erythema and Blood Flow Responses to Acute Ultraviolet Radiation Exposure

Acute exposure to ultraviolet (UV)‐B light elicits an inflammatory response in the skin, resulting in erythema (reddening) and increased skin blood flow over the following 24 hours. However, the time course of, and relation between, these responses is unclear. Likewise, it is unknown whether these responses differ following exposure to broad spectrum (UV‐AB) vs. UV‐B light, as well as how application of sunscreen on the skin impacts these two responses.PurposeTo examine (1) the time course of erythema and skin blood flow responses over 8 h following acute UV‐B and UV‐AB exposure, and (2) the impact of sunscreen application on those responses. We hypothesized that (1) the erythema and blood flow responses would track each other, (2) both responses would be higher following UV‐AB compared to UV‐B exposure, and (3) sunscreen would attenuate responses to both UV‐AB and UV‐B.MethodsThe ventral aspect of both forearms of 10 healthy young adults (25±4 yrs; 6M/4F) were exposed to either UV‐AB (10 mJ/cm2; 6 mJ/cm2 UVA + 4 mJ/cm2 UV‐B) or UV‐B (4 mJ/cm2). Two 2‐cm2 sites on each arm were randomly chosen for acute UV exposure with or without pre‐treatment with topical SPF‐50 sunscreen. Erythema index (EI; reflectance spectrometry) and red cell flux (laser‐Doppler flowmetry) were measured at each site before, immediately after, and 2, 4, 6, and 8 h post‐exposure. Cutaneous vascular conductance was calculated (CVC=flux/MAP) at each time point and both EI and CVC were expressed as change from baseline.ResultsEI increased linearly after exposure to UV‐B (p<0.01 at 4, 6, and 8 h post‐exposure) and UV‐AB (p=0.02 at 6 h, p<0.01 at 8 h). Unlike the immediate increase in EI, no increase was seen for CVC until 4 h post‐UV‐B (p<0.01) and UV‐AB (p=0.06). Sunscreen effectively blocked the EI response to both UV‐B and UV‐AB exposures (p>0.05) and prevented, the CVC responses to UV‐B (p<0.01 at 6 and 8 hours) and UV‐AB (p=0.03 at 8 h).ConclusionExposure to UV‐B or UV‐AB induced an immediate and linear increase in EI, but a delayed (by 4 h) increase in CVC. Sunscreen prevented the EI response and blunted the rise in CVC. These data suggest that the inflammatory response to acute UV exposure is characterized by an immediate erythema response and a delayed blood flow response in the cutaneous microvasculature and that sunscreen may protect against both responses.Support or Funding InformationACSM Foundation Doctoral Student Research GrantThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The Modulating Effects of Sunscreen and Simulated Sweat on Ultraviolet Radiation‐ Induced Microvascular Dysfunction in the Human Cutaneous Vasculature

After acute ultraviolet radiation (UVR) exposure, nitric oxide (NO)‐mediated vasodilation is attenuated in the cutaneous microvasculature, likely via increased oxidative stress. Application of sunscreen to the skin protects from, while sweat on the skin may exacerbate, deleterious effects of UVR, including the erythema. However, it is unknown whether the presence of sunscreen or sweat on the skin influences the effect of UVR exposure on NO‐dependent vasodilation, a marker of skin vascular health.PurposeTo compare the impact of acute UVR, UVR with sunscreen (+SS), and UVR with simulated sweat (+SW) on NO‐mediated vasodilation in the cutaneous microcirculation. We hypothesized that +SS would blunt and +SW would augment the reduction in NO‐dependent vasodilation following acute UVR exposure.MethodsThree intradermal microdialysis fibers were placed in the ventral skin of the left forearm and a single fiber was placed in the right forearm of 13 healthy adults (24±1 yr; 6M/7F) with mild to moderate skin pigmentation (M‐index 30–46). Sites on the left forearm were randomly assigned to UVR exposure (450 mJ/cm2), UVR+SS (SPF‐50 chemical sunscreen), or UVR+SW (64 mmol Na+, 2.1 mmol K+), while the sight on the right forearm served as a non‐UVR exposed control (CON). Following UVR exposure, a standardized local heating (42°C) protocol induced cutaneous vasodilation. After attaining a plateau blood flow, 15mM NG‐nitro‐L‐arginine methyl ester (L‐NAME; NO synthase inhibitor) was infused at all sites to quantify the NO contribution to cutaneous vasodilation. Red cell flux was measured at each site (laser‐Doppler flowmetry) and cutaneous vascular conductance (CVC=flux/MAP) was expressed as a percentage of maximum (%CVCmax; 28mM sodium nitroprusside+43°C) for each phase of the local heating response. The NO‐mediated contribution (%NO) was calculated as the difference between the local heating and L‐NAME plateaus.ResultsThere were no differences in %CVCmax between treatments at baseline (p≥0.55), initial peak (p≥0.40), or heating plateau (p≥0.44). However, UVR blunted %NO compared to CON (CON: 40.8±4.8 vs UVR: 28.0±6.7%; p<0.01). The attenuation in %NO was prevented by sunscreen (UVR: 28.0±6.7 vs UVR+SS: 54.5±5.8%; p<0.01) and by simulated sweat (UVR: 28.0±6.7 vs UVR+SW: 45.8±5.2%; p<0.01). Further, when sunscreen was applied prior to UVR, UVR exposure actually augmented %NO compared to CON (UVR+SS: 54.5±5.8% vs CON: 40.8±4.8; p<0.01) or when sweat was on the skin (UVR+SS: 54.5±5.8 vs UVR+SW: 45.8±5.2%; p<0.01).ConclusionAcute broad spectrum UVR exposure attenuates NO‐mediated vasodilation in the cutaneous microvasculature. The presence of sunscreen or sweat on the skin may play a protective role against this effect, and UVR may actually augment NO‐mediated vasodilation in the presence of a chemical sunscreen.Support or Funding InformationACSM Foundation Doctoral Student Research Grant #17‐00552 and NIH T‐32 Grant #5T32AG049676‐03This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

When to apply sunscreen: a consensus statement for Australia and New Zealand

IntroductionCancers of the skin are the most common cancers in humans, with Australia and New Zealand having the world’s highest incidence. Primary prevention campaigns advise people to apply sunscreen to exposed body sites when outdoors. However, despite growing evidence that cumulative sub‐erythemal exposures cause mutational damage, and trial data demonstrating benefit from daily sunscreen use, current policies do not consider the hazards of incidental (everyday) sun exposure. Thus, a Sunscreen Summit was convened to review the evidence and update the policies for people living in Australia and New Zealand. ResultsAfter reviewing the benefits and risks of sunscreen application, the policy group concluded that people living in Australia and New Zealand should be advised to apply sunscreen to the face/head/neck and all parts of the body not covered by clothing on all days when the ultraviolet index is forecast to reach three or greater, irrespective of their anticipated activities. For planned outdoors activities, sunscreen should be used alongside other sun protection measures. ConclusionsPeople living in Australia and New Zealand are now advised to apply sunscreen every day when the UV index is predicted to reach 3 or above. Implications for public healthIncreased use of sunscreen as part of the daily routine to reduce incidental sun exposure will lead to decreased incidence of skin cancer in the future.

Characterization of tanning behavior assessed via online survey: Attitudes, habits, and preventive measures with focus on sunscreen use.

Incidence of melanoma is increasing globally. Exposure to ultraviolet radiation (UVR) as important risk factor for developing skin cancer can be influenced by tanning behavior. Only a few studies are available concerning sun tanning behavior and protective measures. An online survey was distributed via social media to assess tanning habits and examine associated demographic and behavioral factors. In total, 403 questionnaires were distributed, and mean age of respondents was 32. Having a tanned skin, feeling warm and relaxed were the most common motivations for tanning. The use of sunscreen varied and seemed to depend on the occasion of UVR exposure, constantly applied during vacation and during tanning, less commonly applied in daily life and during work. Avoiding painful solar dermatitis was more important as motivation for the use of sunscreen than skin cancer prevention. Skin aging as reason for the use of sunscreen was especially important for females younger than 26years. The most common applied sun protection factor was 16-49. The main reason opposing the use of sunscreen was a too laborious usage, which was significantly associated with male. Beauty was the only association related to tanned skin the majority (62%) agreed with. The motivation for tanning and reasons for avoiding sunscreen strongly varies. Knowledge about these factors could be used for improving campaigns with respect to target groups. Clarifying the appropriate application of sunscreen, developing convenient sunscreen formulations and providing information about UVR-induced skin aging could lead to an increased usage of sunscreen and therefore to an improved UVR protection.

Nanostructured Zn-Ti layered double hydroxides with reduced photocatalytic activity for sunscreen application

The harmful effects of long-term UV exposure on human skin are increasingly understood these days, and therefore, the use of topical sunscreen products containing UV filters has significantly increased. Although the currently used organic and inorganic UV filters are effective UV absorbers, they may cause several problems such as high photoreactivity, photodegradation, and generation of reactive oxygen species leading to serious skin damages including skin cancer. Therefore, the development of safer, skin-compatible, photostable, and more effective photoactive ingredients is critical. In this study, a Zn-Ti layered double hydroxide (Zn-Ti LDH) was prepared using a hydrothermal method, and its properties as a sunscreen additive were evaluated and compared to those of nano-TiO2 and nano-ZnO. Physical characterization confirmed the formation of a highly stable crystalline LDH structure. Scanning electron microscopy analysis revealed the formation of two-dimensional nano-flakes and layered structure. The optical properties of Zn-Ti LDH analyzed by diffuse reflectance UV-Vis showed higher UV reflection properties and lower absorption properties in comparison to TiO2 and ZnO. Zn-Ti LDH exhibited substantially lower levels of photocatalytic activity towards the degradation of methylene blue at both 365 nm and 254 nm which indicates increased safety of Zn-Ti LDHs for use as UV filters in topical sunscreen applications.

Increased UV absorption properties of natural hydroxyapatite‐based sunscreen through laser ablation modification in liquid

AbstractSunfilters based on hydroxyapatite (HAp) and iron‐containing compounds (Fe2O3 and calcium iron phosphates) are of increasing interest, as they show UV absorption without generating health endanger free radicals (usually observed when other inorganic sunscreens are used). In this paper, laser ablation of solids in liquids has been applied to improve the UV absorption properties of a HAp based Fe‐containing sunscreen powder derived from cod fish bones. Two different laser wavelengths were explored (532 and 1064 nm, green and infrared, respectively); an improved experimental device was used, to allow a fine control of the volume of the irradiated particles. Results show an increased UV absorbance for the laser‐treated powders in comparison with the untreated ones; this can be explained considering the smaller particle size and increased surface area; the higher iron concentration in the powders may also be determinant. Enhanced absorption was also observed in the near‐infrared range, making the powders even more suitable for sunscreen applications. The green laser was more effective than the infrared one. Overall, laser ablation showed to be a powerful technique to control the size of the sunscreen particles and tailor their optical properties.

Gas chromatographic-mass spectrometric analysis of sunscreens and their effects on mice liver and kidney enzyme function.

BackgroundSunscreens are one of the most widely used products among cosmetics and personal care products. Recent studies have shown that some of sunscreen formulations may contain toxic, carcinogenic, or even nonallowed chemicals that may affect skin, cells, and hormones.Materials and methodsThis study aimed to develop and validate a method that allows the determination of sunscreen ingredients by gas chromatography–mass spectrometry (GC–MS). Analysis of original sunscreen products (n=5) from a licensed pharmacy and counterfeit sunscreen products (n=5) from local markets in Jordan was performed using GC–MS. pH stability of the sunscreen samples were also monitored under different storage temperatures. Topical application of sunscreens on mice skin was conducted to study their effects on liver and kidney enzymes’ function.ResultsIn terms of pH stability, there is a significant change in pH at different degrees of temperature between the products. Diethyl phthalate (DEP) was detected in two counterfeit products and was not mentioned on the ingredients’ label. DEP was reported for its percutaneous absorption and systemic uptake in the literature. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were significantly increased with a P<0.005 in some groups treated with original sunscreens under sun radiation. Creatinine showed a significant decrease in some groups treated with original and counterfeit sunscreens, while blood urea nitrogen (BUN) showed no differences.ConclusionThis study presents a method that allows the scanning and profiling of sunscreen ingredients as well as investigates their stability, permeation, and toxicity. Profiling of sunscreen product, changing in pH stability, and analyzing kidney and liver enzymes’ level would be of a great impact on products’ safety and consumers’ health.

Sunscreen application to the face persists beyond 2 hours in indoor workers: an open-label trial

Background: The American Academy of Dermatology recommends reapplication of sunscreen every two hours for adequate sun protection when outdoor. However, the frequency of reapplication needed to achieve adequate protection in indoor workers remains unknown.Objective: To investigate the persistence of sunscreen applied once in the morning on the face of indoor workers throughout a normal 8-hour workday.Methods: This open-label trial included 20 healthy volunteers who work indoors. Volunteers applied 1 g of sunscreen (2 mg/cm2) mixed with 2% invisible blue fluorescent agent on the face in the morning. Photographs were taken by VISIA-CR booth in UV mode at 8 am and then every 2 hours thereafter until 4 pm with limited outdoor activity less than 1 hour. Six areas of the face were analyzed using digital image analysis software. The primary outcome was the total amount of sunscreen diminution during the 8-hour study period.Results: The amount of sunscreen decreased with mean peak reduction of 16.3% at 2 hours, and minimal reduction thereafter. Total sunscreen reduction was 28.2% at the end of the 8-hour day.Limitations: Small study population.Conclusion: For indoor workers who applied adequate amount of sunscreen once in the morning, reapplication of sunscreen may be unnecessary.

Efficient UV Filter Solubilizers Prevent Recrystallization Favoring Accurate and Safe Sun Protection.

Sun protection is a global concern, and maximizing sunscreen stability and efficacy depends partially on the prevention of UV filters recrystallization. We aimed to study the efficacy of hydrophobic solubilizers in preventing the recrystallization of solid hydrophobic UV filters in predissolutions, sunscreen formulations, and during simulated human use. Recrystallization of UV filters induced by ultrasonication, temperature variation, or simulated human application was analyzed by different methods. Maximum solubility of UV filters in solubilizers was determined. Surprisingly, the best solubilizer was not necessarily the best solvent to prevent recrystallization, suggesting there are different forces controlling these phenomena. Hydrophobic solubilizers tend to perform better than ethanol in predissolutions, but the presence of other components in final products may change their performance. Results suggest that some UV filters tend to form liquid clusters, which may behave as crystals and affect the desired even distribution of UV filters on the skin. UV filters were also found to respond differently to Hansen Solubility Parameters. Scanning electron microscopy supports the fact that recrystallization upon sunscreen application is an issue to be tested during development. A timesaving method to predict recrystallization of UV filters in clear systems was developed and is presented as a tool to enhance the efficacy of sunscreens.

Lignin for white natural sunscreens

Long-time exposure to the sun's ultraviolet (UV) radiation is harmful and causes various skin problems. Natural sun blockers have been drawing considerable attention recently. Even though lignin, an abundant aromatic polymer from plants, is a natural UV screening agent, its unfavorable dark color hinders its high value-added applications in sunscreens and cosmetics. In this study, we separate lignin under mild conditions (at room temperature with neutral solvents) in order to prevent darkening occurring during delignification and apply the resultant lignin as a natural sunscreen ingredient for the first time. Lignins isolated from Miscanthus sacchariflorus (MWL-M) and from Pinus densiflora (MWL-P) are compared with organosolv lignin (OL), which showed the best sunscreen performance, in color and UV protection. MWLs separated under mild conditions were light in color unlike conventional lignins extracted under harsh conditions. UV absorption of light-colored MWL-M was revealed to be as high as dark-colored OL. MWLs also showed synergistic effects with a commercial sunscreen; exposure of the MWL-added sunscreen to UVA radiation greatly enhanced the sun protection factor (SPF) value of the sunscreen.

Acculturation, Biculturalism and Cancer Risk and Preventive Behaviors Among Pacific Islander Immigrant Youths in Hawaii

Background: Culture is an important force which affects health behaviors linked to cancer risks among immigrants. Studies have demonstrated the process of acculturation can produce a form of stress that impact health negatively. On the other hand, research suggests that biculturalism, defined as the combining and practicing of customs from two cultures, may be a healthy approach to acculturation. Biculturalism is especially relevant for youth immigrants as their cultural identities are still developing. Pacific Islanders, a fastest growing populations in the US, often experience discrimination in the society at large and in the health care system. Pacific Islander youth in the US navigate between two cultural identities: their native culture as they live in a close-knit community that still maintains strong cultural norms and values, and the dominant American culture that they face once they step outside their community. This is one of the rare studies that examine the relationship between acculturation and cancer preventive behaviors among Pacific Islander youth. Aim: We aim to study the process through which biculturalism influences cancer risk and preventive behaviors such as smoking, sunscreen applications, physical activity and healthy eating among Pacific Islander youth immigrants in Hawaii. Specifically, we map the process of influence that links biculturalism to self-esteem and to these cancer risk and preventive behaviors. Methods: Using survey data from 284 Pacific Islander youth, we developed and tested a theoretically driven model that specifies the relationship among variables listed above. Results: Results show that self-esteem serves as an important mediator connecting biculturalism to cancer preventive behaviors. While biculturalism did not have a direct influence on behaviors and outcomes, it led to increased self-esteem which, in turn, directly influenced attitudes about sunscreen application, physical activity and healthy eating. However, there was neither direct nor indirect link between biculturalism and smoking. Conclusion: While numerous studies have shown links between biculturalism and health, not many studies focus on the specific process through which the influence is exerted. This study provides an important insight into the process through which biculturalism impacts cancer preventive behaviors among minority youth in America. Data from the study showed a clear relationship between biculturalism, self-esteem, their attitudes and behavior related to cancer prevention among Pacific Islander youth living in Hawaii. This study provides insights into potentially novel methods and interventions designed to increase cancer preventive behaviors among migrant youth by dually promoting adoption of U.S. cultural norms, while concurrently embracing an individual´s historic cultural identity.

Synthesis and characterization of novel 4-aminobenzoate interleaved with zinc layered hydroxide for potential sunscreen application

4-aminobenzoic acid (4-AB) interleaved with zinc layered hydroxide (ZAB) was successfully synthesized from 4-AB and zinc oxide (ZnO) by using co-precipitation method. The PXRD pattern of ZAB with a basal spacing of 23.2 A has confirmed that 4-AB interleaved into zinc layered hydroxide (ZLH) inorganic interlayer. The interleaved compound was also verified with the presence of COO– and aromatic N–C groups observed at 1518 cm−1 and 1174 cm−1, respectively, in the FTIR spectrum. The results were supported by the presence of 18.7% carbon composition in the ZAB material obtained from TGA analysis. Morphological studies showed that ZAB material is a flake-like shape with different sizes. Further characterizations of the resulting compounds were also studied by using BET/BJH, ICP and CHNS analyses.

Tannin-Titanium Oxide Multilayer as a Photochemically Suppressed Ultraviolet Filter.

UV filters can initiate redox reactions of oxygen and water when exposed to sunlight, generating reactive oxygen species (ROS) that deteriorate the products containing them and cause biological damages. This photochemical reactivity originates from the high chemical potential of UV filters, which also determines the optical properties desirable for sunscreen applications. We hypothesize that this dilemma can be alleviated if the photochemical pathway of UV filters is altered to coupling with redox active molecules. Here, we employ tannic acid (TA) as a key molecule for controlling the photochemical properties of titanium dioxide nanoparticles (TiO2 NPs). TA provides an unusual way for layer-by-layer assembly of TiO2 NPs by the formation of a ligand-to-metal charge transfer complex that alters the nature of UV absorption of TiO2 NPs. The galloyl moieties of TA efficiently scavenge ROS due to the stabilization of ROS by intramolecular hydrogen bonding while facilitating UV screening through direct charge injection from TA to the conduction band of TiO2. The TiO2-TA multilayers assembled in open porous polymer microspheres substantially increased sun protection while dramatically reducing ROS under UV exposure. The assembled structure exhibits excellent in vivo anti-UV skin protection against epidermal hyperplasia, inflammation, and keratinocyte apoptosis without long-term toxicity.

Skin Cancer Knowledge, Attitudes, and Practices among Chinese Population: A Narrative Review.

Skin cancers are becoming a substantial public health problem in China. Fair skin and increased exposure to ultraviolet B (UVB) rays from the sun are among the most substantial risk factors for skin cancer development, thus making the Chinese people vulnerable to this group of diseases. The purpose of this article is to present a narrative review of the knowledge, attitudes, and practices (KAP) related to skin cancers within the Chinese population. A systematic electronic search of MEDLINE (PubMed), CINAHL, ScienceDirect, and Google Scholar databases yielded nine articles that met the inclusion criteria. The review found that although sunscreen application was a commonly used method of skin protection among the general Chinese population, educational interventions enhancing current knowledge and attitudes about the effects of UVB rays on skin from undue sun exposure were limited in many smaller communities of the country. Hence, there is an essential need to design effective, evidence-based educational programs promoting sun protection behaviors in both congregated and sparsely populated areas of China.

Mesoporous Silica and Organosilica Nanomaterials as UV-Blocking Agents.

Mesoporous silica nanoparticles (MSN) and periodic mesoporous organosilica nanoparticles containing bridging benzene (PMOBTB) and ethane (PMOBTE) moieties are synthesized, characterized, and evaluated for application in skin protection from UVA/UVB sun irradiation. Furthermore, the influence of surface functionalization with chelating 3-(2-aminoethylamino)propylsilane and Zn2+ ions on the UV-blocking ability of MSN is evaluated, along with the photostability and capability of the synthesized nanomaterials to carry avobenzone, a known UV-absorbing agent. The obtained results reveal promising characteristics of MSN and PMO materials with regard to their potential for sunscreen applications, which could be beneficial in terms of alleviating concerns about health and environmental hazards of sunscreen ingredients.

Comparative behavior between sunscreens based on free or encapsulated UV filters in term of skin penetration, retention and photo-stability

BackgroundThe growing incidence of photodamaging effects caused by UV radiation (e.g. sunburn, skin cancer) has increased the attention from health authorities which recommend the topical application of sunscreens to prevent these skin damages. The economic stakes for those companies involved in this international market are to develop new UV filters and innovative technologies to provide the most efficient, flexible and robust sunscreen products. Today the development of innovative and competitive sunscreen products is a complex formulation challenge. Indeed, the current sunscreens must protect against skin damages, while also being safe for the skin and being sensory and visually pleasant for the customers when applied on the skin. Organic UV filters, while proposing great advantages, also present the risk to penetrate the stratum corneum and diffuse into underlying structures with unknown consequences; moreover, their photo-stability are noted thorny outcomes in sunscreen development and subsequent performance. In recent years, the evaluation of the interaction between skin and sunscreen in terms of penetration after topical application has been considered from European authority but still its testing as their photo-stability assessment are not mandatory in most countries. ObjectiveThis study, based on in-vitro approaches, was performed to evaluate and compare the retention and the penetration of organic UV filters in free or encapsulated form inside the skin as well as their respective photo-stability. MethodsSunscreen formulation with a combination of Avobenzone and Octocrylene in “free form” and a formulation using the same UV filters but encapsulated in a sol-gel silica capsule, were analyzed and compared by FTIR Imaging Spectroscopy. Tape stripping method was used to investigate the penetration of these UV filters inside the stratum corneum. Their photo-stabilities were evaluated by spectroscopic measurements (FTIR, UV/Vis) and standard measurements were calculated: AUC (Area Under the Curve) and SPF (Sun Protection Factor). ResultWith traditional formulation, the organic UV filters penetrated significantly into the stratum corneum while the same UV filters combined with encapsulation technology remained on the skin surface. The encapsulation technology also improved significantly their stability. ConclusionEncapsulation technology is a promising strategy to improve the efficacy of sunscreen product using organic UV filters and to reduce safety problem. On the other hand, this study highlighted the pertinence of the FTIR Spectroscopy to test, compare and investigate sunscreen formulations.

Sun protection in children: a behavioural study

Incidence of skin cancer is increasing worldwide and UV exposure at a young age is an important risk factor. To compare sun exposure-related knowledge and behaviour among children during school and holiday periods. A cross-sectional study was undertaken at 12 Oporto public primary schools. Educational sessions for educators were head by dermatologists every spring from 2004 to 2012. An educational activity book, Play and Learn with Jo Spots, was distributed to all primary school children and was explained by the educators every year. A questionnaire about sun exposure and behaviour was given to students in 2004 and 2012. In total, 2,114 students answered the questionnaire (1,233 in 2004 and 881 in 2012). Children practiced more outdoor sports in 2012 than in 2004 (86% vs 56%; p<0.001), but spent less time outside when the sun's rays were most dangerous. The use of hats (64% vs 59%; p=0.028) and sunscreen (35% vs 15%; p<0.001) at school and the application of sunscreen before going to the beach improved over time (51% vs 26% in 2004; p<0.001). However, there was an increase in sunburn rate (43% vs 37%; p=0.005). Sun exposure-related behaviour among primary school students in Oporto is improving but is still far from optimal. School would appear to be an adequate setting for effective and long-lasting sun protection interventions, and the introduction of educational books at schools, such as Play and Learn with Jo Spots, might be effective in bringing about positive behavioural changes.

1167 The impact of trace amounts of long wavelength UVA1 on visible light induced effects

Our skin is exposed to visible light (VL) and long wavelength ultraviolet A1 (UVA1) radiation (370-400 nm) present in sunlight even after application of organic broad spectrum sunscreens. The effects of these wavelengths on pigmentation and erythema have been demonstrated. However, a dose response has not been investigated which can provide insight on how skin responses can vary based on the duration of sun exposure. Ten subjects with Fitzpatrick skin phototype IV-VI were enrolled. On day 0, subjects were irradiated with two light source; one comprising pure VL and the other VL with less than 0.5% UVA1 (VL+UVA1) at a dose of 80 J/cm2, 160 J/cm2, 320 J/cm2 and 480 J/cm2. The irradiance was set at 175 mW/cm2. Skin responses were evaluated immediately, at 24 hours, 7 days, and 14 days after irradiation. Assessment methods included investigator’s global assessment (IGA), diffuse reflectance spectroscopy (DRS), and colorimetry. Clinical IGA scores suggest that 3/10 subjects for the 320 J/cm2 site, and 5/10 subjects for the 480 J/cm2 site had clinical erythema immediately after irradiation on the VL+UVA1 side only. No erythema was observed for the corresponding pure VL sites. Only the highest dose, 480 J/cm2,resulted in pigmentation response that was statistically significantly different at all time points between the two light sources (p<0.05). Pigmentation response from VL+UVA1 site was two times more intense than that of pure VL at the day 14 time point. Spectroscopy and histology data analysis are under progress. Wavelengths not covered by current broad spectrum sunscreens have implications on pigmentation and erythema. There appears to be a threshold dose of UVA1 which in combination with VL results in immediate erythema followed by darker and persistent pigmentation. The effects can be noticed at approximately two hours of outdoor sun exposure.

In vitro water resistance testing using SPF simulation based on spectroscopic analysis of rinsed sunscreens.

Water resistance retention (WRR) is the third performance attribute of sunscreens. Today, the standardized method for testing WRR is performed in vivo. For screening purposes, an in vitro method is highly preferable. Up to now, however, available methods have failed in accurately predicting in vivo WRR. In this study, we examine a novel in vitro approach aimed at enhancing in vivo prediction of WRR. We investigated two approaches, including a traditional procedure referred to as the 'plate method', which involves measuring in vitro sun-protection factor (SPF) before and after water immersion, and a new approach termed the 'solution method'. The latter employed a computational method to calculate the SPF using UV transmittance measurements of a sunscreen solution, obtained by rinsing the substrate without water immersion and with water immersion. It also had a model function for describing film irregularity. The aim was to avoid the effect of substrate-to-product affinity on the film distribution, which impacts the measured absolute value of the in vitro SPF occurring in the conventional approach. For both methodologies, we assessed two substrates for the sunscreen application based on different polymers, the widely used polymethylmethacrylate (PMMA) and the ethylene methacrylate acid copolymer (EMA). The agreement between in vivo and in vitro WRR values obtained from each of the four test conditions was analysed using different sunscreens. No correlation was found between in vivo and in vitro WRR using the plate method, independently of the plate type. In contrast, the solution method, using EMA plates, revealed a significant correlation between in vivo and in vitro results, with an especially high correlation for in vivo non-water-resistant sunscreens. The results of two operators were comparable. The solution method was unsuitable for PMMA plates. Despite the small discrepancy remaining between WRR values obtained from the in vitro solution method and in vivo method, which itself shows variability in results, this work provided a new insight into the in vitro testing of water resistance of sunscreens.

Sunscreen use optimized by two consecutive applications.

Sunscreen users are often inadequately protected and become sunburned. This study aimed to investigate how much two consecutive sunscreen applications increased the quantity of sunscreen applied and decreased the skin area left without sunscreen (missed area) compared to a single application. Thirty-one healthy volunteers wearing swimwear were included and applied sunscreen two consecutive times in a laboratory environment. Participants had pictures taken in black light before and after each application. As sunscreens absorb black light, the darkness of the skin increased with increasing amounts of sunscreen applied. We conducted a standard curve establishing a link between change in picture darkness and quantity of sunscreen. The quantity of sunscreen at selected skin sites as well as the percentage of missed area was determined after each application. Participants had missed a median of 20% of their available body surface after a single application. After double application they had missed 9%. The decrease in missed areas was significant for the whole body surface and for each of the body regions separately. The median participant had applied between 13% and 100% more sunscreen at the selected skin sites after double application than after single application. We recommend double application, especially before intense sun exposure.