Optimal sunscreen use allows vitamin D synthesis

Vitamin D, vital for bone health, is produced by the skin in response to ultraviolet radiation (UVR) from sunlight. However, as well as being the main source of vitamin D, UVR is a major cause of skin cancer. This has led to questions about how to prevent low levels of vitamin D whilst limiting the risk of skin cancer. This study, led by researchers from King's College London, found that use of sunscreen did not prevent most people from getting enough vitamin D whilst on a week-long holiday to an area with a very high UV index. Whilst on holiday, 20 people received a broad-spectrum sunscreen with a Sun Protection Factor (SPF) of 15, offering UVB protection and high UVA protection. Another 20 received a non-broad-spectrum sunscreen, also SPF 15 but with low UVA protection. These two groups were told how to use their sunscreens correctly to achieve the labelled SPF. In contrast, 22 people used their own sunscreen with no instructions on application, and 17 people formed a control group who remained in Poland. Blood samples were taken from participants 24 hours before and 24 to 48 hours after the holiday to check vitamin D levels. The first two groups saw a highly significant improvement in vitamin D levels. The group that used their own sunscreens also had significant vitamin D synthesis, but all had sunburn. During the same period, the control group had a slight decline in vitamin D.     

Does chronic sunscreen use reduce vitamin D production to insufficient levels?

Exposure to ultraviolet B radiation in sunlight provides the mechanism for more than 90% of the vitamin D production in most individuals. Concern has been expressed in recent years that the widespread use of sunscreens, particularly those with high sun protection factors, may lead to a significant decrease in solar-induced previtamin D₃ in the skin, resulting in a vitamin D level which is considered insufficient for protection against a wide range of diseases. In this article the published evidence to support and to question this view is presented. It is concluded that, although sunscreens can significantly reduce the production of vitamin D under very strictly controlled conditions, their normal usage does not generally result in vitamin D insufficiency.     

Risk reduction for nonmelanoma skin cancer with childhood sunscreen use

Exposure to ultraviolet radiation is the principle cause of basal and squamous cell carcinomas of the skin, which are the most frequent tumors occurring in white residents of the United States. Using a mathematical model based on epidemiologic data, we quantified the potential benefits of using a sunscreen with a sun protective factor of 15 and estimate that regular use of such a sunscreen during the first 18 years of life would reduce the lifetime incidence of these tumors by 78%. Additional benefits of sunscreen use during childhood include reduced risk of sunburn, retarding the pace of skin aging, and possible reduction in melanoma risk. We recommend that pediatricians encourage sunscreen use and sun avoidance as a regular part of pediatric preventive health care.     

Application patterns among participants randomized to daily sunscreen use in a skin cancer prevention trial

BACKGROUND: Despite many investigations of sunscreen use, there have been few among adults in the community at large. Better understanding of sunscreen application patterns will lead to more strategic skin cancer prevention strategies among sun-exposed populations. OBJECTIVE: To explore patterns of sunscreen use, particularly the quantity of sunscreen used and the application frequency, among participants in a community-based sunscreen intervention. DESIGN: Follow-up of patterns of sunscreen use over 4.5 years. SETTING: Nambour, a subtropical town in Queensland, Australia. PARTICIPANTS: People drawn randomly from the electoral register who were later randomized as part of a skin cancer prevention trial. INTERVENTIONS: Daily application of a standard sun protection factor 15+ broad-spectrum retail sunscreen to the head and neck, arms, and hands. OUTCOME MEASURES: Frequency of application of sunscreen, weight of sunscreen applied, and quantity applied per unit area of skin. RESULTS: Fifty-six percent of participants reported applying sunscreen on at least 5 days per week, with 27% using sunscreen infrequently on 2 or fewer days per week. The median daily amount of sunscreen applied averaged over the duration of the trial was 1.5 g/d (range, 0-7.4 g/d). The median quantity of sunscreen applied was 0.79 mg/cm(2), which was less than half the amount needed to achieve the labeled sun protection factor. CONCLUSIONS: It is possible to implement the daily application of sunscreen in sun-exposed populations, although protection would be increased if the quantity of sunscreen applied were greater.     

Sunbed use in relation to phenotype, erythema, sunscreen use and skin diseases. A questionnaire survey among Swedish adolescents

Summary Sunbed use was studied in relation to phenotype, erythema, sunscreen use and skin disease. The study population comprised 14–19 year-old Stockholm adolescents in 60 randomly selected classes, with 1252 students providing information. More than half (57%) reported sunbed use ± 4 times during the previous year. Skin type III dominated (64%). Excessive exposure (± 10 times/year) was not correlated to skin type. Sunscreens were most commonly used by sunbed users. Of all sunbed users, 44% reported erythema. Adolescents with acne/seborrhoea, eczema or psoriasis used sunbeds more than others without skin diseases. The proportion with sunbed erythema (44%) indicates an unrecognized susceptibility to artificial ultraviolet radiation (UVR) among adolescents. The association between high exposure to UVR and sunscreen use stresses the importance of sunscreens being used as supplementary protection , not as a tool for tanning.     

Sun protection and sunscreen use after surgical treatment of basal cell carcinoma

Sixty-three patients (mean age 54± 9 years) who were treated for a basal cell carcinoma (BCC) and 54 control subjects (mean age 51± 11 years) filled out detailed questionnaires on their sun exposure and sun protection habits. Patients were given the questionnaires at least 1 year after their skin tumors had been excised. Differences between patients and controls in mean age, gender, Fitzpatrick's skin type and eye and hair color were statistically nonsignificant. The level of education was high in both patients and controls (mean of 13.4± 3.1 school years). Differences in education were statistically nonsignificant. We found that both patients and controls were knowledgeable about the role of sunscreens in preventing skin tumors (79% and 83% respectively) and in preventing sun-induced aging (90% and 85% respectively). Significantly more patients used sunscreens regularly (64%) compared with controls (36%). Nevertheless, our data show no statistically significant differences between the sun exposure habits of the patients previously treated for BCC and controls. Moreover, we found that, although 82% of the patients declared that they tried to avoid sun, only 49% regularly wore hats or shirts with long sleeves in the summer (19%). Sixty-two percent of the patients used two or fewer bottles of sunscreens per year, which is inadequate for effective year-round sun protection. In addition, we found that many patients, as well as the controls, applied sunscreens only once a day (57% and 46% respectively), did not reapply after swimming (58%, 74% respectively), and did not use sunscreens in the winter (49%, 61%). Our data show that, although patients after BCC removal have a significantly higher sunscreen use compared with controls, the amount and methods of application are less than adequate. Moreover, other simpler methods to prevent photodamage, such as simple sun avoidance or the use of protective clothing, are often neglected.     

The effects of chronic sunscreen use on the histologic changes of dermatoheliosis

Background: Sunscreen application to the skin of hairless mice is effective in reversing the histologic changes associated with photoaging (solar elastosis, epidermal thickening, collagen depletion, glycosaminoglycan deposition). These reparative processes have not been studied in human beings.Objective: The aim of this study was to evaluate histologically the effects of daily application of a UVA/UVB sunscreen versus placebo.Methods: We examined 46 patients who were given either sunscreen or vehicle and asked to apply it daily for 24 months. Punch biopsy specimens were obtained from preauricular skin at 0, 12 and 24 months. Each specimen was examined for epidermal thickening and organization and dermal inflammatory infiltrate by light microscopy. Computer-generated analysis of tissue sections was used to evaluate solar elastosis.Results: A significant difference in solar elastosis was found between the treatment groups; however, the other features remained largely unchanged.Conclusion: The dermal changes of photoaging may be affected differently than epidermal changes when UV radiation exposure is diminished. UVA and UVB may contribute diversely to these cutaneous changes. Computer-generated evaluation of dermatoheliosis may be more accurate than visual inspection.     

Phototoxicity to a sunscreen ingredient. Padimate A

Para-aminobenzoic acid and certain of its esters are widely used in sunscreens. We found that one of these, amyl paradimethylaminobenzoate (padimate A) was capable of provoking phototoxic reactions; With ultraviolet A (UV-A) dosages of about 30 joules/sq cm, a reaction grossly resembling sunburn developed in most subjects. The dominant histological feature was vacuolar degeneration of the epidermis without sunburn cells. Proprietary sunscreens containing padimate A were also shown to produce a similar reaction. Our explanation for the paradox of a sunscreen that promotes "sunburn" is that, as affected users have concluded, the product was ineffective. The similarity between sunburn and a phototoxic response has delayed recognition of this adverse effect until now.     

Cutaneous malignant melanoma, sun exposure, and sunscreen use: epidemiological evidence

Summary Background  Cutaneous malignant melanoma is the most serious form of skin cancer and accounts for about three-quarters of all skin cancer deaths. Over the last few decades the incidence and mortality rates of melanoma have been increasing worldwide. The risk of melanoma is higher in individuals with both phenotypic susceptibility and a history of sun exposure. Therefore, recommended sun protection behaviours include wearing long-sleeved clothing, seeking shade, avoiding the sun when it is strongest, and using sunscreen lotion with a sun protection factor of 15 or higher. It has been reported, however, that the use of sunscreens does not protect against melanoma and seems to increase the duration of recreational sun exposure.
Methods  Published epidemiological studies examining sunscreen use and melanoma have been reviewed from an epidemiological point of view, taking into account potential biases. We have classified case–control studies into four categories: (1) inconclusive studies because of major bias in control population and/or the lack of multivariate analysis; (2) no association between sunscreen use and melanoma after controlling for confounders; (3) negative association (i.e. protective effect of sunscreen); and (4) positive association. Various other epidemiological studies were also analysed.
Results  These results are controversial. Two case–control studies show a protective effect of sunscreen use, while three studies showed a significant risk associated with sunscreen use. However, the discordant results, the low relative risks, the lack of dose–effect relationship and the numerous biases, especially the uncertainty that exposure (sunscreen use) preceded melanoma do not suggest a causative association between sunscreen use and melanoma. Several hypotheses could partly explain these contradictory results.     

Rates of allergic sensitization and irritation to oxybenzone-containing sunscreen products: a quantitative meta-analysis of 64 exaggerated use studies

Background/purpose: Oxybenzone is an active ingredient found in sunscreen products that absorbs a broad spectrum of ultraviolet (UV) light, with absorbance peaking in the UVB region and extending into the UVA region. Although the overall incidence of sensitization and irritation associated with oxybenzone in the general population remains unclear, a few studies have reported on the incidence in specific circumstances. However, the relevance of these studies to the general population is limited, because the sample populations reported in these papers generally have consisted of individuals who sought medical attention for pre‐existing skin conditions. Therefore, the reported incidence of allergic reactions to oxybenzone in these studies may be overestimated as related to the general population. The objective of this meta‐analysis was to determine the safety of oxybenzone in participants recruited from the general population. Methods: The data from 64 unpublished exaggerated use human repeat insult patch tests (HRIPT) and photoallergy (PA) studies sponsored by Schering‐Plough HealthCare Products Inc. between 1992 and 2006 were aggregated and analyzed to evaluate the irritancy and sensitization potential of sunscreen products containing oxybenzone at concentrations between 1% and 6%. Results: Forty‐eight of 19 570 possible dermal responses were considered to be suggestive of irritation or sensitization; the mean rate of responses across all formulations was 0.26%. Sensitization rates did not correlate significantly with oxybenzone concentration. The available re‐challenge data indicated that only eight of these responses were contact allergies from oxybenzone, and the mean rate of contact allergy to oxybenzone was 0.07%. The source of the skin responses was not confirmed for 15 subjects who were lost to follow‐up. However, all subjects were given the opportunity to participate in follow‐up testing. Conclusion: Our data indicate that sunscreen products formulated with 1–6% oxybenzone do not possess a significant sensitization or irritation potential for the general public. Furthermore, these data suggest that the incidence rate implied in the published literature overestimates the actual incidence of sensitization/irritation due to oxybenzone‐containing sunscreen products in the general population.