The influence of pre-irradiation on the predictability of in vivo UVA protection with a new in vitro method

BACKGROUND/PURPOSE: UVA protection of sunscreen formulations is becoming increasingly important especially because of recent investigations on the long-term skin damage associated with UVA light. The development of a new in vitro method to measure UVA protection performance made it possible to predict reliably the in vivo UVA protection performance of representative sunscreen formulations found presently in the European and US market (1). This study was performed in order to determine the applicability of the method developed by Wendel et al. (1) to photostable and photolabile filter combinations and in order to measure the influence of sample pre-irradiation on predicting the in vivo performance. This was done by subjecting six photostable and six photolabile filter combinations to a standard irradiation. Then the in vitro UVA protection afforded by each combination was measured and compared with the persistent pigment darkening (PPD) values determined in vivo. RESULTS: The results clearly showed that pre-irradiation does not affect the in vitro PPD factor of the photostable and photolabile samples in the same way. Almost identical values were determined for the stable filter combinations with and without pre-irradiation, whereas distinct reductions in the in vitro factors by as much as 93% were observed after irradiation in the group of less stable filter combinations. Comparison of the in vivo and in vitro PPD factors showed that all 12 samples comprise a homogeneous distribution with identical factors before irradiation. After pre-irradiation only the factors for the six less stable products were selectively reduced. The correlation with the data determined on the skin was clearly poorer for these products after irradiation. CONCLUSION: Overall, the results showed that pre-irradiation should not to be used for the assessment of UVA protection using this method. Furthermore, it can be assumed that normalizing the in vitro absorbance curves to the labelled SPF of the sunscreen will adequately take into account the photochemical behaviour of UV filters on the skin during sun exposure.     

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。     

Solar keratosis: epidemiology, pathogenesis, presentation and treatment

Solar keratosis is a common problem encountered by dermatologists, particularly in Australia. Solar keratosis is most commonly found on sun-exposed areas such as the scalp, face and forearms. UV radiation is thought to be the major aetiological factor, with age, immunosuppression and human papillomavirus being important contributing factors. Solar keratosis usually presents as a discrete, variably erythematous and irregular lesion with a scaly surface. Although the exact rate of malignant transformation to squamous cell carcinoma is unknown, the majority of squamous cell carcinomas appear to arise from within solar keratosis. For this reason, solar keratosis is commonly treated and, consequently, an increasing number of therapeutic options is now available. Traditional therapies, such as liquid nitrogen cryotherapy, are still popular, but newer choices, such as photodynamic therapy and imiquimod cream, are now providing further options with similar efficacy and superior adverse effect profiles, albeit at a higher cost.     

Percutaneous absorption of the sunscreen benzophenone-3 after repeated whole-body applications, with and without ultraviolet irradiation

BACKGROUND: Benzophenone-3 (BZ-3; 2-hydroxy-4-methoxybenzophenone, oxybenzone) is commonly used to absorb ultraviolet (UV) radiation. BZ-3 penetrates the skin and can be found in the urine. The amount varies between 0.4% and 2%. This seems to be the main metabolic pathway in rats. OBJECTIVES: To investigate the total amount of BZ-3 excreted in the urine after repeated topical whole-body applications of a sunscreen and to see if UV radiation has any effect on the amount excreted. METHODS: Twenty-five volunteers applied a commercially available sunscreen containing 4% BZ-3 morning and night for 5 days. Their urine was measured during those 5 days and during a further 5 days after the last application. They were divided into groups A (unirradiated) and B. Group B received UV radiation according to skin type: UVA between 400 and 707 J cm(-2), and UVB between 0.46 and 2.0 J cm(-2). BZ-3 in urine was analysed with a high-performance liquid chromatography method. RESULTS: The volunteers excreted 1.2-8.7% (mean 3.7%) of the total amount of BZ-3 applied. There was no significant difference between the two groups (P < 0.99, t-test). CONCLUSIONS: We show that a large amount of BZ-3 is absorbed. BZ-3 is accumulated in the body as the volunteers excreted BZ-3 5 days after the last application.     

Relevance of UV filter/sunscreen product photostability to human safety

Photostability or photo‐instability of sunscreen products is most often discussed in undesirable terms with respect to human safety. The health risks, specifically associated with sunscreens, photostable or photo‐unstable, include phototoxic/photoirritation or photoallergic responses and, longer‐term, an increased risk of skin cancers or photoageing. The aims of this paper are to define photostability/photo‐instability and objectively assess the acute and chronic toxicological consequences from the human exposure to UV filter/sunscreens and any probable photo‐degradation products. The reported prevalence of photoirritation and photoallergic responses to sunscreens is rare compared with adverse events, for example, skin irritation or sensitization, produced by cosmetics or topically applied drugs and do not directly implicate potential photo‐degradation products of UV filters. Moreover, for at least one photo‐unstable combination, octyl methoxycinnamate and avobenzone, the long‐term benefits to humans, i.e., reduction in skin cancers, seem to outweigh any potential adverse consequences attributed to photo‐degradation. Sunscreen products are formulated to achieve maximum efficacy which, by necessity and design, incorporate measures to support and promote photostability since all organic UV filters have the potential to photo‐degrade. Current performance measures, in vivo SPF and in vitro UVA, conducted under standardized conditions, in part account for photostability. The concerns expressed when considering human exposure to potential photo‐unstable UV filters or sunscreen products may not manifest as health risks under conditions of use. Still, improvement in sunscreen product photostability continues to be a key strategic objective for manufacturers.     

Active sunscreen ingredients in Australia

UV radiation exposure is the major contributor to photocarcinogenesis and photoageing. Reducing UV radiation exposure can be achieved by using adequate sunscreen preparations. The use of sunscreen can significantly reduce the incidence of squamous cell carcinoma, actinic keratoses and invasive melanoma. In the Australian market over 900 sunscreen products are available, each with their own brand, formulation and ingredients. It can be difficult for dermatologists and consumers to determine which are the most effective and appropriate products to use. We discuss the specific active ingredients found in sunscreen formulations available in Australia, their mode of protection, photostability, solubility, and side‐effects and the methods used by the Therapeutic Goods Administration to determine the ratings and efficacy of each sunscreen.