Photopatch testing: a consensus methodology for Europe

A group of interested European Contact Dermatologists/Photobiologists met to produce a consensus statement on methodology, test materials and interpretation of photopatch testing. While it is recognized that a range of local variables operate throughout Europe, the underlying purpose of the work is to act as an essential preamble to a Pan European Photopatch Test Study focusing particularly on sunscreen chemicals.     

Uniformity of sunscreen product application: a problem in testing,a problem for consumers

BACKGROUND/AIMS: Testing of sunscreen products requires application of uniform films of product of defined thickness to test volunteers. In spite of the seeming importance of product application to defining sunscreen efficacy, there have been few studies determining how well uniformity is achieved. The purpose of this work was to evaluate the uniformity of sunscreen products of different sun protection factors (SPFs) and vehicles on a variety of substrates by in vitro testing techniques. The results of a variety of testing strategies are reported. METHODS: Five commercial sunscreen products of labelled SPF 4-50 were tested using a variety of substrates: Transpore Tape, Vitro-Skin trade mark, and lambskin condom. Two experienced sunscreen testers applied the products. In vitro SPFs were determined using an Optometric 290 analyser or an Optronic Laboratories OL754 spectroradiometer configured for this application. RESULTS: SPFs for several locations on each film applied to a substrate were determined and the mean SPF and RSD percentage of the mean calculated. For all substrates and testing techniques the average RSD percentage was 18.6, with a range of 10-40%. CONCLUSION: The expected uncertainty of SPF due to product application non-uniformity is 20% when applied under optimal test conditions. Clearly SPF tests reported by different laboratories must exhibit significant variability, because of product application non-uniformity.     

Is daily use of sunscreens of benefit in the U.K.?

BACKGROUND: There is an increasingly widespread belief that year-round use of topical agents containing ultraviolet (UV)-absorbing ingredients is an important factor in reducing the chronic degenerative cutaneous changes associated with sun exposure. OBJECTIVES: To evaluate the benefit of using sunscreens during different periods of the year for people living in the U.K. METHODS: An analysis was made of typical solar UV exposure at different times of the year in relation to different topical sunscreen practices. RESULTS: It was shown that using sun protection products during the six summer months (April-September) can reduce the lifetime (70 years) UV exposure of a person by an equivalent of almost 40 years unprotected exposure. However, virtually no benefit is gained from using UV protective products from October to March in the U.K. CONCLUSIONS; As their use is not without cost and the risk of adverse effects, topical products containing UV filters are best avoided during October to March in the U.K.     

Determination of threshold UV-A elicitation dose in photopatch testing

Photopatch testing, although widely used in the diagnosis of photosensitivity disorders, is not Standardized. We performed this study to determine the threshold ultraviolet tight A (UV-A) dose required to elicit photopatch test responses. 4 patients with previously positive tests were reexposed to the offending allergen, using an incremental dosage regime. Isopropyl dibenzoylmethane (Eusolex 8020), mexenone (benzophenone-10) and oxybeozone (benzophenone-3) produced positive responses at 1.0, 1.0 and 0.7 J/cm², respectively. Responses to phenothiazines were deemed phototoxic. These results demonstrate that high doses of UV-A (e.g., 10–15 J/cm²) are unnecessary, and that 5 J/cm² should become the current Standard.     

Determination of UVA protection factors using the persistent pigment darkening (PPD) as the end point. (Part 1). Calibration of the method

BACKGROUND/AIMS: The accuracy and reliability of any method to assess the UVA protection effectiveness of sunscreens needs to be demonstrated. The aim of the present study was to calibrate the effectiveness of a biological end point (Persistent Pigment Darkening, PPD) to assess UVA photoprotection, METHODS: Persistent Pigment Darkening was selected as the end point because its action spectrum extends across the UVA. A broad UVA source was chosen to challenge all UVA wavelengths. Attenuation of UVA was performed with neutral density filters (equally absorbing at all wavelengths). Human subjects were tested with a series of UVA beams attenuated by the neutral density filters. The UVA protection effectiveness of a standard sunscreen was also tested with four panels of volunteers to assess the reproducibility of the method. RESULTS: The attenuation factors of the neutral density filters were found to correspond to the UVA protection factors arrived at with PPD as the end point. The repetitive tests showed a good internal consistency of the method. CONCLUSIONS: The calibration procedure proposed shows threshold PPD, used as an end point in a UVA-PF test method, to be a reliable endogenous dosimeter for UVA radiation that enters the skin.     

Sunscreens as a preventative measure in melanoma: an evidence-based approach or the precautionary principle?

Background  Meta-analyses of observational case-control studies have demonstrated no association between sunscreen use and the development of malignant melanoma.
Objectives  To postulate whether modern sunscreens are likely to be effective as a preventative agent in melanoma and, if so, how many cases might be avoided by their use.
Methods  The potential number of melanomas prevented by encouraging the use of modern, high SPF, broad spectrum sunscreens during recreational summer exposure was estimated by combining the prevalence of their use with the relative risk of melanoma in nonusers compared with those people who regularly use these products.
Results  Notwithstanding the inherent uncertainties and assumptions that this approach involves, it is shown that significant numbers of melanomas might be avoided by regular sunscreen use during recreational summer sun exposure, and with them appreciable financial, social and emotional costs, even for very modest estimates of the benefit of broad-spectrum sunscreens.
Conclusions  Despite the lack of evidence demonstrating the efficacy of modern sunscreens in preventing melanoma, it is argued that it would be irresponsible not to encourage their use, along with other sun protection strategies, as a means of combating the year-on-year rise in melanoma incidence.