UV-induced immune suppression and sunscreen

Sun protection factor (SPF) that measures sunscreen protection against erythema and edema may not be enough to measure a sunscreen's activity against many other biologic reactions induced by ultraviolet radiation (UV). It may be better to evaluate sunscreen efficacy using various tools including immune protection factor (IPF), mutation protection factor (MPF) and protection against photocarcinogenesis. In terms of immune protection, sunscreens protected against UV-induced immune suppression significantly. But protection in some cases was partial and often the IPF of sunscreens were less than the SPF. IPF may differ with various immunological endpoints, and it may be better to use a couple of different assays to measure sunscreen protection more objectively. Sunscreen use protects against most UV-induced non-melanoma skin cancers and actinic keratoses but its activity against melanoma is not clear. More studies with broad-spectrum stable sunscreens and better models for the investigation of malignant melanoma are required.     

Sunscreens used at the beach do not protect against erythema: A new definition of SPF is proposed

Since sunscreens are recommended by doctors and used all over the world to protect against sun induced erythema, it is important to evaluate if sunscreens are used as recommended and if the intended effect is achieved. We refer to the findings of several studies performed on people at risk of sun-burning at beaches in the vicinity of Copenhagen, Denmark. On a sunny day at the beach 65% of the sunbathers used one or more sunscreens. Of these, 46% used the sunscreen all over the body and a median sun protection factor (SPF) of 5–6 was used. The sunbathers used 0.5 mg/cm² of sunscreen independent of skin type. Of the sunscreen users, 43%> applied the sunscreen after arriving at the beach and 43% reapplied the sunscreen after swimming. The sun exposure time and the sun exposure dose were almost identical among sunscreen users and non-users. Self-assessed redness of the skin demonstrated that more sunscreen users than non-users reported to be red the day after sun exposure, 42 and 34%, respectively. Theoretical calculations support this finding and show a drastic reduction in the achieved photoprotection if a thinner layer than in the test situation is used. Sunscreens do not protect against erythema if not used as intended. Instead of changing people's habits, we suggest modifying the test method by adjusting the amount of sunscreen to that used in real life situations, 0.5 mg/cm².     

Comparison of three techniques for evaluating skin erythemal response for determination of sun protection factors of sunscreens: high resolution laser Doppler imaging, colorimetry and visual scoring

BACKGROUND/PURPOSE: Sun protection factor (SPF) measurement is based on the determination of the minimal erythema dose (MED). The ratio of doses required to induce a minimal erythema between product-treated and untreated skin is defined as SPF. The aim of this study was to validate the conventionally used visual scoring with two non-invasive methods: high resolution laser Doppler imaging (HR-LDI) and colorimetry. Another goal was to check whether suberythemal reactions could be detected by means of HR-LDI measurements. MATERIALS AND METHODS: Four sunscreens were selected. The measurements were made on the back of 10 subjects. A solar simulator SU 5000 (m.u.t., Wedel, Germany) served as radiation source. For the visual assessment, the erythema was defined according to COLIPA as the first perceptible, clearly defined unambiguous redness of the skin. For the colorimetric determination of the erythema, a Chromameter CR 300 (Minolta, Osaka, Japan) was used. The threshold for the colorimetry was chosen according to the COLIPA recommendation as an increase of the redness parameter delta a* = 2.5. For the non-contact perfusion measurements of skin blood flow, a two-dimensional high resolution laser Doppler imager (HR-LDI) (Lisca, Link?ping, Sweden) was used. For the HR-LDI measurements, an optimal threshold perfusion needed to be established. RESULTS: For the HR-LDI measurements basal perfusion +1 standard deviation of all basal measurements was found to be a reliable threshold perfusion corresponding to the minimal erythema. Smaller thresholds, which would be necessary for detection of suberythemal responses, did not provide unambiguous data. All three methods, visual scoring, colorimetry and HR-LDI, produced similar SPFs for the test products with a variability of < 5% between methods. The HR-LDI method showed the lowest variation of the mean SPF. Neither of the instrumental methods, however, resulted in an increase of the sensitivity of SPF determination as compared with visual scoring. CONCLUSION: Both HR-LDI and colorimetry are suitable, reliable and observer-independent methods for MED determination. However, they do not provide greater sensitivity and thus do not result in lower UV dose requirements for testing.     

Field-based measurements of personal erythemal ultraviolet exposure through a common summer garment

The research in this paper quantifies the solar erythemal UV exposures to the skin through a common summer garment during outdoor activities. The erythemal exposures under the garment for the wet white garment exceeded a MED (minimum erythemal dose) at some anatomical sites in summer for a two-hour period. An erythemal exposure of 1.7 MED, in excess of the occupational limit for UV exposure, was measured under the white garment during swimming for a one-hour period. Clothing must form an important component of a UV protection strategy. However, it must be realised that total UV protection is not provided and significant UV exposures may be received beneath the garment, particularly for a white garment in the wet state. This re-enforces the necessity of a combination of several UV prevention strategies to minimise UV exposure.     

Sun protective clothing in Australia and the Australian/New Zealand standard: an overview

Clothing has been part of the sun protection strategy for many years. However, it is only recently that studies have been undertaken to investigate the protectiveness of fabrics and to place clinical advice on a sound scientific basis. Fabrics can now be rated and an ultraviolet protection factor assigned. Several factors influence photoprotection such as construction, stretch, hydration, colour, fibre type and various manufacturing processes. In 1996 the Australian/New Zealand Standard for sun protective clothing was published. This is the first of its kind in the world.     

北京地区人群对防晒霜的认知及使用情况

目的了解北京地区人群对防晒霜的认知及使用情况。方法采取问卷调查方式,进行面对面交谈,并填写调查问卷。结果80.3%(578/720)的人使用过防晒霜,女性明显高于男性(P<0.001)。开始使用防晒霜的年龄为8～60岁,平均28.4±22.0岁,平均使用时间8.1±21.7年。35.8%的男性、34%的中老年人、44.6%的初等文化程度及28.3%的Ⅳ,Ⅴ型皮肤的人群从未使用过防晒霜。女性及Ⅰ,Ⅱ型皮肤的人使用防晒霜比较规律。63.1%的人群使用防晒霜SPF值在15～30之间。17.3%的人不知道自己使用防晒霜的SPF值,以男性、中老年、初等文化者以及Ⅳ、Ⅴ型皮肤人群为主。有一半以上的人不知道防晒指数的意义。结论北京地区人群中使用防晒霜的比例较高。在对防晒霜的认知和使用,不同人群差异较大。     

Diffuse reflectance spectroscopy for ultraviolet A protection factor measurement: correlation studies between in vitro and in vivo measurements

Background/purpose: Assessing the ultraviolet (UVA) protection factor of sunscreen formulations has been discussed for the past 20 years. The purpose of this study is to correlate the measurements of the UVA protection factor value (PFA value) via in vivo diffuse reflectance spectroscopy (DRS) and to compare this method with the in vitro method of measuring the PFA value, as well as with the in vivo persistent pigment darkening (PPD) and PFA methodologies.
Methods: The UVA protection factor via DRS technique was assessed in two clinical studies. The first study was performed in 12 subjects and the second one consisting of 10 subjects. All subjects in these studies had Fitzpatrick skin phototypes II–IV. DRS measurements were performed using a SkinScan spectrofluorimeter (Spex SkinScan, Yvon Horiba). The in vitro PFA measurements were performed using Labsphere^™ UV-1000s UV Transmission Analyzer.
Results: The results obtained from the non-invasive DRS studies were used to correlate with the in vitro testing and with the in vivo PFA/PPD multicenter study. A positive relationship (regression coefficient r ²=0.90) of PFA values was found between in vitro PFA testing and the in vivo DRS testing. There was also a very good correlation (regression coefficient r ²=0.99) between the in vivo PFA/PPD values and UVA protection factor obtained from the DRS method.
Conclusion: This paper presents studies using the DRS technique to assess the UVA protection factor in different sunscreen formulae correlating with in vitro and in vivo PFA/PPD values. It is a fast method, non-invasive and does not involve any subject irradiation. The technique is a good estimator for the in vivo UVA protection factor as well as a way to assess, in vivo , the photostability of sunscreen formulation in the UVA.     

SPF290分析系统与人体试验测定日光防护指数的比较研究

日光防护指数是评价遮光剂防止紫外线晒伤作用的一个重要指标。本实验通过人体试验方法和ＳＰＦ２９０分析系统体外试验方法分别测试了１２种遮光剂样吕的ＳＰＦ值。结果显示两种方法之间有很好的相关性，用两种方法测得的ＳＰＦ值间均无显著性差异。     

The influence of the amount of sunscreen applied and its sun protection factor (SPF): evaluation of two sunscreens including the same ingredients at different concentrations

Background: To estimate labeled sun protection factor (SPF) for sunscreen, the amount of product applied on volunteers, according to food and drug administration (FDA) and International protocols, is 2 mg/cm². However, different studies have shown that consumers actually apply much less product when exposed to the sun. Previous studies have reported contradictory findings in an attempt to correlate the amount applied in relation to SPF. The objective of the present study was to estimate the influence of the quantity of sunscreen applied in the determination of SPF, according to the FDA methodology.
Subjects and methods: Forty volunteers were included in two groups (SPF 15 and 30). The selected sunscreen was then applied in four different quantities (2, 1.5, 1.0 and 0.5 mg/cm²). All areas were irradiated with a solar simulator. After 24 h, the minimal erythemal dose (MED) and SPF were determined.
Results: In both groups, we observed that the SPF decreased when the amount of sunscreen applied was decreased. The differences between the 2 mg/cm² area and the others were significant in both groups ( P <0.001). The correlation between specified SPF and applied amount grew exponentially.
Conclusion: The protection provided by sunscreen is related to the amount of product applied. It is essential to educate consumers to apply larger amounts of sunscreen for adequate photoprotection.     

Sunscreen application by photosensitive patients is inadequate for protection

Photosensitive patients often comment that sunscreen products seem of little benefit. We used fluorescence spectroscopy to assess quantitatively their sunscreen application technique. A dose-response relationship for sunscreen skin surface thickness and fluorescence intensity was determined for an intrinsically fluorescent sunscreen, Neutrogena sun protection factor (SPF) 15. Ten women with long-standing photosensitivity conditions were asked to apply this sunscreen in the manner they would normally on a bright sunny day. Fluorescence measurements were taken from all unclothed body areas, comprising 17 sites of the head, neck, upper and lower limbs. Geometric regression analysis of the dose-response data showed a high level of correlation (r = 0.99) between sunscreen thickness and fluorescence intensity, allowing fluorescence measurements to be converted to an equivalent sunscreen thickness. The overall median sunscreen thickness was 0.5 mg/cm2, with median thicknesses of individual sites ranging from 0 to 1.2 mg/cm2. The most frequently missed sites were the posterior neck, lateral neck, temples and ears, all of which had median thicknesses of 0 mg/cm2. Hence, photosensitive patients fail to apply sunscreen in some prominently exposed sites, and use average thicknesses far less than the manufacturers' recommendation (2 mg/cm2). The level of protection is much lower than anticipated from the stated SPF of the product.     

Sun protection factor persistence during a day with physical activity and bathing

Background/purpose: The persistence of sunscreens during a day with physical activity and bathing is often debated. We wished to examine the durability of the protection achieved by one sunscreen application. Methods: Seven areas were marked on the back of 24 volunteers. One area was phototested to determine UV sensitivity. Six areas were treated with either an organic or an inorganic sunscreen (2 mg/cm²). The participants performed physical activities, were exposed to a hot environment and bathing during 8 h and were phototested with ultraviolet‐B (UVB) radiation 30 min, 4 and 8 h after sunscreen application. The minimal erythema dose (MED) was determined 24 h after irradiation. The sun protection factor (SPF) was calculated, as MED on protected skin/MED on unprotected skin. Results: The SPFs of the inorganic and organic sunscreen, respectively, were reduced by 38% and 41% after 4 h and by 55% and 58% after 8 h. Conclusion: One application of either an inorganic or an organic sunscreen reduced the erythema caused by UVB during a day with physical activity and bathing. After 8 h the sunscreens still provided approximately 43% of the initial protective effect. This might simulate what happens during a day at the beach.     

Lichtschutz: Möglichkeiten und Grenzen

Protection against ultraviolet (UV) irradiation prevents from the development of acute skin damage such as erythema formation and chronic skin changes such as premature skin ageing. Especially those sunscreens with higher sun protection factors do not only protect against solar dermatitis but also inhibit UV‐induced immunosuppression by blocking the release of immunosuppressive mediators from UV‐exposed epidermis. In particular, the protection against UV‐induced immunosuppression by sunscreens is supposed to reduce the development of UV‐induced skin cancer. Besides immunosuppression UV‐irradiation is also able to induce “UV signature” mutations within UV‐exposed DNA. Topical application of DNA repair enzymes induces nucleotide excision repair and corrections of DNA damages. Thereby, the risk to develop UV‐induced skin malignancies is markedly reduced. Accordingly, future perspectives in the development of sunscreens include DNA repair enzymes or factors, which can induce the endogenous cellular DNA repair system. Until these developments come to practice reasonable sun protection according to the skin complexion is of primary importance.     

New sunscreens confer improved protection for photosensitive patients in the blue light region

BACKGROUND: Some patients with photosensitivity disorders are sensitive to visible radiation. As current commercial sunscreens do not significantly absorb in this region, there is a lack of effective topical photoprotection. To meet this need a new range of sunscreens has been developed incorporating zinc oxide and pigmentary grade titanium dioxide as active ingredients. OBJECTIVES: To determine the effectiveness of the new sunscreens in providing protection for patients with visible radiation photosensitivity. METHODS: In the first part of this study, an in vitro transmission spectrum was obtained. The properties of the new sunscreens, as well as a range of commercial agents, were compared, and a new parameter, photosensitivity protection factor (PPF), was developed. This was used to predict the likely degree of protection the various sunscreens would provide for patients with photosensitivity extending into the visible region. In the second in vivo part of the study, patients with known visible (blue) light photosensitivity were tested using light at 430 +/- 30 nm and the protection factor (PF) at this wavelength was determined. RESULTS: Mean +/- SD PPFs for the new sunscreens were between 5.4 +/- 0.3 and 9.6 +/- 0.3, compared with 4.1 +/- 0.1 for Sun E45 (sun protection factor, SPF 25) and 4.2 +/- 0.1 for RoC Total (SPF 25). The derived in vivo PF for Sun E45 ranged between 1 and 4 (median 2). For the new sunscreens the range was 3 to > 10 (median 8). CONCLUSIONS: This study demonstrates that the new sunscreens do provide protection for patients with sensitivity to visible light (blue light region).     

The comparison of sun protection factor values with different light sources.

Sun protection factors (SPFs) were evaluated with three light sources (sunlight, a xenon arc solar simulator, and fluorescent lamps) in indoor and outdoor studies. Two types of light, UV-A+B and UV+Visible, were obtained from the solar simulator. The untanned backs of twenty-four healthy male volunteers were used as test sites. A broad spectrum sunscreen containing SPF 6, according to the manufacturer, was used. The sunscreen tested was applied at 2 mg/cm2. The actual SPF values were 4.8 with sunlight, 6.0 with UV-A+B, 4.9 with UV+Visible, and 11.8 with fluorescent lamps. There were no significant differences between the SPF values with sunlight and those with the solar simulator; the SPF value for fluorescent lamps was significantly higher. The SPF with UV-A+B of the solar simulator was similar to that with sunlight; the use of this light served to reduce pain on tested subjects. Therefore, UV-A+B from the solar simulator seems to be the most appropriate artificial light source for evaluating sunscreens.