A double‐blind,randomized assessment of the irritant potential of sunscreen chemical dilutions used in photopatch testing*

Background: The maximum concentration of organic sunscreen filters in current usage that does not lead to irritant reactions when performing photopatch testing is not known. Such irritant reactions can be misinterpreted as positive photoallergic contact dermatitis reactions. Objective: To determine the frequency of irritant reactions to 19 organic sunscreen filters in current use. Patients/Methods: Ninety‐four healthy volunteers were photopatch tested using the European consensus methodology to three different concentrations (2%, 5%, and 10%) of 19 organic sunscreen filters at the Photobiology Unit in Dundee, UK. Results: Of the 94 subjects recruited, 80 were analysed after withdrawals and exclusions. Of the 19 organic sunscreen filters studied, only 2 compounds led to irritant reactions in ≥5% subjects. Five per cent and 10% benzophenone‐4 led to irritant reactions in four and six subjects, respectively. Five per cent methylene bis‐benzotriazolyl tetramethylbutylphenol led to irritant reactions in six subjects, but unlike benzophenone‐4, this was not in a dose‐dependent fashion. Conclusions: When performing photopatch testing according to the European consensus methodology with these 19 organic sunscreen filters, a 10% concentration is suitable for all filters, except benzophenone‐4, which should be tested at a concentration of 2%.     

Simplified method to substantiate SPF labeling for sunscreen products

BACKGROUND/PURPOSE: Worldwide, sunscreen sun protection factor (SPF) testing is based on 30-year-old technology. At the time the SPF test came into being, the highest SPFs available were in the 6-8 range. The SPF test is reasonably accurate for SPFs up to 15, but is much less reliable for measuring SPFs of 30 and higher. The method we propose addresses two primary reasons for this unreliability: 1) difficulties in applying products uniformly and 2) the subjectivity and variability of perception in evaluating and grading responses to UV doses. METHODS: Our proposed SPF substantiation method differs from the current SPF test in that sunscreen-protected test sites receive the same UV dose in four uniformly spaced sub-sites, which are graded as passing if no response is seen or failing if any response is seen. The response may be tanning, erythema, or a combination of both. To demonstrate the method, two commercial products with labeled SPFs of 30 and 45 and the P2 sunscreen standard were tested at two different laboratories. RESULTS: The SPF 30 product and SPF 15 standard were shown to be correctly labeled. However, it is questionable as to whether the SPF 45 product provides protection against 45 minimal erythema doses. CONCLUSIONS: Our proposed SPF substantiation method is not dependent on subjective evaluation of responses, accounts for non-uniform product application, and provides a conservative estimate of sunscreen protection. The method consists of a systematic repetition of identical tests that are considerably more rigorous than the current methods that are based on single data points per test subject. While the current SPF test remains necessary and valuable as a dose ranging tool, we propose that this SPF substantiation method supersede the old method for final SPF label determination.     

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.     

Modulation of ultraviolet (UV) transmission by emollients: relevance to narrowband UVB phototherapy and psoralen plus UVA photochemotherapy

BACKGROUND: Patients with psoriasis undergoing or about to undergo ultraviolet (UV) phototherapy and photochemotherapy often have thick scale on their plaques which can prevent the penetration of UV radiation. Emollients are used to moisturize the skin and to prevent or reduce some of the milder side-effects ('dryness', itching) sometimes experienced during UV therapy. However, emollients can alter the UV transmission of skin and thus may alter the clinical effects of phototherapy and photochemotherapy. OBJECTIVES: We tested 30 of the topical emollients in the British National Formulary (BNF) using a standard in vitro technique used to test sunscreens. We also surveyed U.K. phototherapy units to establish routine practice for emollient use in phototherapy and photochemotherapy. METHODS: We used a standard in vitro technique to measure the monochromatic protection factors (MPFs) of 30 non-bath emollients from the BNF. An application rate of 2 mg cm-2 was used. For the assessment of effects during narrowband UVB (TL-01) phototherapy, the mean of the protection factors at 310 and 315 nm was calculated; for psoralen plus UVA photochemotherapy the mean UVA protection factor was used. A questionnaire survey was used to assess routine practice concerning emollient use prior to phototherapies in phototherapy units throughout the U.K. RESULTS: In the UVA range, 17 of the 30 emollients gave protection factors of 1.2 or above. In the UVB range, 23 of 30 had an MPF of 1.2 or above. Yellow soft paraffin had the highest protection factor in the UVB range. Of 78 centres surveyed, 57 returned completed questionnaires (73%). Seventeen of 57 (30%) centres routinely used emollients immediately prior to administering phototherapy treatments. The remaining 40 of 57 (70%) did not. Forty-five (79%) responding centres recommended the use of emollients after phototherapy. CONCLUSIONS: This study has revealed considerable variability in the practice of emollient use before phototherapy treatments. Although the majority of centres included in this study did not routinely use emollients, almost one third did. Our in vitro measurement of 30 emollients revealed marked variation in UV transmission, with many emollients blocking sufficient UV to affect the response to therapy.     

In Vitro Human Epidermal and Polyethylene Membrane Penetration and Retention of the Sunscreen Benzophenone-3 from a Range of Solvents

Purpose. To study epidermal and polyethylene membrane penetration and retention of the sunscreen benzophenone-3 (BP) from a range of single solvent vehicles and evaluate solvent effects on permeability parameters. Methods. The solubility of BP was measured in a number of solvents. Penetration of BP across human epidermis and high density polyethylene (HDPE) membranes was studied from 50% saturated solutions in each solvent. Results. Maximal BP fluxes from the solvents across the two membranes varied widely. Highest fluxes were observed from 90% ethanol (EtOH) for epidermis and from isopropyl myristate (IPM) and C_12–15 benzoate alcohols (C_12–15 BA) for HDPE membrane. Both the flux and estimated permeability coefficient and skin-vehicle partitioning of BP appeared to be related to the vehicle solubility parameter (_v). The major effects of solvents on BP flux appear to be via changes in BP diffusivity through the membranes. Conclusions. Minimal penetration of sunscreens such as BP is best achieved by choosing vehicles with a _v substantially different to the solubility parameter of the membrane.     

Randomized controlled community trial of the efficacy of a multicomponent stage-matched intervention to increase sun protection among beachgoers

BACKGROUND: Skin cancer is about as common as all other cancers combined and is preventable by sun protection. The most intense sun exposures often occur on the beach, so we chose this setting to test an intervention to affect sun protection behaviors. METHODS: We developed a multicomponent stage-matched intervention for beachgoers and evaluated its efficacy in a randomized trial for influencing stage of change and self-reported behavior. RESULTS: We randomized 2,324 persons ages 16 to 65 on the beach (83% of those approached). The intervention was effective in increasing self-reported sun protective behaviors. Effects were similar across gender and age groups. CONCLUSIONS; The beach is a good site for recruitment and intervention to prevent skin cancer in high-risk populations. Our stage-matched intervention package was effective for increasing sun protective behaviors.     

An update of the pathogenesis of frontal fibrosing alopecia: What does the current evidence tell us?

Frontal fibrosing alopecia (FFA) is a primary patterned cicatricial alopecia with a complicated pathogenesis yet to be fully understood. FFA appears to be increasing in incidence worldwide, especially in the last decade. In order to consider current treatment options, we reviewed current evidence for its pathogenesis comprising immune-mediated, genetic, hormonal and environmental factors. Th1-mediated inflammation with collapse of hair follicle immune privilege and bulge epithelial stem cell destruction, peroxisome proliferator-activated receptor gamma (PPAR-γ) depletion and epithelial–mesenchymal transition are key events leading to permanent hair follicle destruction in FFA. Although the vast majority of cases are sporadic, familial reports of FFA implicate genetic or epigenetic mechanisms in its pathogenesis. The frequent onset of FFA in post-menopausal women, similar patterning and co-existence with female pattern hair loss, together with a reportedly good response to 5α-reductase inhibitors suggest a role for sex steroid hormones. The reported increasing incidence invites speculation for, yet unproven, environmental triggers such as sun exposure and topical allergens. More robust research into this unique entity is required to help understand the complexity of the pathogenesis of FFA in order to find satisfactory therapeutic targets for this often distressing condition.