Mark D. Farrar

Background: Sun exposure guidance advises minimisation to reduce skin cancer risk, but advice is geared for white-skinned people. Melanin reduces skin synthesis of vitamin D from solar ultraviolet radiation (UVR), and adolescence is a key life-stage for bone mass acquisition. Methods: This prospective cohort study investigated year-round vitamin D status and its determinants in 143 South Asian adolescents (12–15 y; brown skin) living in Greater Manchester, UK. Serum 25OHD, personal UVR doses, time outdoors, and photoprotective measures were assessed across four seasons, and the findings were compared with those of 131 white Caucasian adolescents studied using identical protocols. Results: Severe vitamin D deficiency (25OHD < 25 nmol/L) was prevalent in South Asians, affecting 79% of girls and 69% of boys in winter, persisting year-round in 59% of girls and 23% of boys, and accompanied by winter PTH levels > the upper reference range in 59% of boys and 45% of girls. Personal UVR doses and time outdoors were lower on summer weekend days (boys 53 min, girls 60 min) vs. schooldays (boys 105 min, girls 108 min) in South Asians (p < 0.01). The findings contrasted with those in white Caucasians, where time outdoors was similar on summer weekend days and schooldays (weekend days: boys 131 min, girls 101 min, p < 0.01 vs. South Asians). Only 26% of South Asians vs. 86% of white Caucasians took a holiday abroad during the year, and days abroad significantly contributed to vitamin D status. Both groups had low oral vitamin D intake. Conclusions: Raising vitamin D status is crucial to prevent secondary hyperparathyroidism in South Asian adolescents and skin type-related sun exposure guidance is required.

Skin acts as the body’s first line of defense against environmental insults including ultraviolet radiation (UVR) from sunlight and engages in a dynamic dialog with the resident skin microbiota, increasingly recognized for its role in shaping and educating the immune responses of the skin in both health and disease. However, how or indeed if the resident skin microbiota mediates inflammatory responses to sunlight remains unclear. To address this, we investigated the effects of five abundant members of the skin microbiota on cytokine secretion in human primary keratinocytes exposed to a single dose of UVB. Co-culture of primary keratinocytes with a defined five-species skin commensal community resulted in a broad increase in the secretion of innate immune mediators including interleukin-6 (IL-6), independent of UVB exposure. In the absence of UVB, Staphylococcus epidermidis was the dominant species, followed by Staphylococcus hominis within the five-species community. UVB induced a marked shift in community composition, characterized by increased proliferation of S. hominis and reduced S. epidermidis abundance, as confirmed by species-specific growth curve analyses. Assessment of species-specific effects using mono-associated host cells revealed S. epidermidis as the predominant contributor to the enhancement of immune mediator secretion. Without the presence of additional community members , UVB amplified S. epidermidis -induced cytokine secretion. However, co-culture of S. epidermidis with S. hominis attenuated the heightened inflammatory response to UVB typically associated with S. epidermidis , likely due to the reduced abundance of S. epidermidis following UVB exposure. These findings suggest that the resident skin microbiota may contribute to our inflammatory response to sunlight. IMPORTANCE: This study reveals that the skin microbiome may play a role in shaping inflammatory responses to UVB exposure. It provides evidence of organisms capable of both amplifying and mitigating inflammatory responses to UVB, highlighting the importance of microbial composition in photoprotection. These findings suggest individual responses to sunlight may be influenced not only by skin type but also by specific microbes present on the skin.

Background: Solar urticaria is a rare photodermatosis in which exquisite photosensitivity can require extreme behavioural adaptations, resulting in a substantial impact on quality of life (QoL). Omalizumab therapy has been demonstrated to improve several clinical outcome measures, but the impact on behavioural measures is poorly understood. Our objectives were to examine daylight exposure behaviours and QoL measures pre‐ and post‐omalizumab therapy. Methods: Daylight exposure diaries were completed by n = 5 patients with solar urticaria and n = 7 healthy participants during different seasons in England, UK (51.1–53.5 ^o N). These incorporated a range of measures, including time spent outdoors and clothing worn, and Dermatology Life Quality Index (DLQI) data were also collected. Results: Prior to omalizumab, patients spent less time outdoors in sunny vs. non‐sunny conditions in spring (mean 10 vs. 29 min/day, p < 0.05) and less than healthy volunteers (44 min in sunny conditions/day). On omalizumab, patients increased their time outdoors in sunny conditions, reaching similar levels to healthy volunteers in spring (45 min/day) and further increasing to 85 min/day in summer. This was accompanied by fewer days with symptoms (symptoms on 75% days in spring pre‐omalizumab vs. 26% days in summer on omalizumab), an apparent doubling of skin surface area exposure and substantial improvement in patients' QoL (mean past‐year DLQI pre‐omalizumab vs. past‐week summer on omalizumab 22 vs. 5, p < 0.001). Conclusion: Omalizumab therapy was associated with behavioural changes that increase daylight exposure, accompanied by improved QoL. This study highlights the importance of considering a range of outcome measures in assessing response to therapy.

Human skin comprises diverse epithelial, mesenchymal, immune and appendage-associated cell populations organised within structured spatial niches. Whilst single-cell RNA sequencing defines transcriptional states, it lacks spatial resolution and accurate mapping within intact tissue. Here, we introduce a high-resolution spatial single-cell profiling framework for human skin to achieve comprehensive cellular annotation in situ. This approach resolves transcriptionally similar and low-abundance populations across epidermal, dermal and appendage compartments, including basal and suprabasal keratinocytes, fibroblast subsets, melanocytes, endothelial and mural cells, and resident immune populations. In skin exposed to inflammatory ultraviolet irradiation, the platform delineates the immune infiltrate at single-cell resolution and captures Langerhans cell egress from the epidermis, demonstrating its capacity to resolve dynamic tissue responses. By improving sensitivity, spatial fidelity and cross-compartment coverage, this framework provides a scalable reference atlas of human skin and establishes a foundation for mechanistic interrogation of tissue organisation, niche interactions and inflammatory remodelling.

Solar Urticaria (SU) is a rare, chronic inducible urticaria characterised by an itching or burning erythemal flare with or without whealing, that | POSTER

Loss and remodelling of the dermal extracellular matrix (ECM) are key features of photodamaged human skin. Green tea catechins (GTCs) have been explored for their anti‐inflammatory and chemopreventive properties, but data on the impact of GTCs on ultraviolet radiation (UVR)‐induced changes to the dermal ECM are lacking. To investigate the effect of an inflammatory dose of solar‐simulated UVR on human dermal ECM and potential for protection by GTCs in a double‐blind randomized controlled trial. In total, 50 healthy white (Fitzpatrick skin type I–II) adults aged 18–65 years were randomized to a combination of GTCs 540 mg plus vitamin C 50 mg or to placebo twice daily for 12 weeks. The impact of solar‐simulated UVR at 3 × minimal erythema dose on the dermal collagen and elastic fibre networks was assessed by histology and immunohistochemistry in all participants at baseline. The impact of GTC supplementation on UVR‐induced effects was compared between the groups post‐supplementation. The area of papillary dermis covered by collagen and elastic fibres was significantly lower (P < 0.001) in UVR‐exposed skin than in unexposed skin. Significantly lower levels of fibrillin‐rich microfibrils (P = 0.02), fibulin‐2 (P < 0.001) and fibulin‐5 (P < 0.001) were seen in UVR‐exposed than unexposed skin, while procollagen‐1 deposition was significantly higher in UVR‐exposed skin (P = 0.01). Following GTC supplementation, the UVR‐induced change in fibulin‐5 was abrogated in the active group but not the placebo group, with no difference between the two groups for other components. Acute UVR induced significant changes in the human dermal collagen and elastic fibre networks, whereas oral GTCs conferred specific UVR protection to fibulin‐5. Future studies could explore the impact of GTCs on the effects of repeated suberythemal UVR exposure of human skin.

Vitamin D₃ can be produced by exposing skin to UVB radiation or sourced through dietary products. It is often stated that vitamin D status declines in older adults, yet little is known about differences in current-day lifestyle and dietary behaviours influencing vitamin D outcomes in younger (18–40 years old) and older adults (65–89 years old). Our objectives were to perform a pilot study to compare sun exposure behaviours, i.e., time spent outdoors, holiday behaviour and use of sunscreen/clothing, and dietary vitamin D intake, in young and older adults in the UK, together with assessment of their vitamin D status. A total of 13 young and 11 older volunteers completed a four-page questionnaire to assess sun exposure and photoprotective behaviour and an eleven-page one-week vitamin D diet diary, alongside their plasma 25(OH)D measurement. It was found that the older group tended to spend more time outdoors during the working week in summer, to take more summer and winter holidays each year, take longer winter holidays and have similar sunscreen use when compared to younger adults. Older adults had a significantly higher daily dietary intake of vitamin D (4.0 μg) than young adults (2.4 μg). Mean winter 25(OH)D concentration was higher in older (56.9 nmol/L) than in young adults (43.2 nmol/L), but there was no statistical difference between the groups. Contrary to common assumptions, in this study, older adults had sun exposure and dietary behaviours conferring a vitamin D status at least as good as that of younger adults.