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Open research questions in Skin Protection and Aging

51 unresolved questions extracted from the limitations and future-work sections of 370 Skin Protection and Aging papers in our library. Each links back to the study that raised it.

What the literature leaves open

  • As markers of angiogenesis such as CD31 staining or microvessel density were not quantified, our find- ings are limited to the modulation of VEGF expression rather than providing definitive evidence of an anti-angiogenic effect.

    The Protective Potential of Terpenoid-Rich <i>Canarium odontophyllum</i> Miq. Leaves against 7,12-Dimethylbenz[ <i>a</i> ] anthracene and Ultraviolet B-induced Two-stage Skin Carcinogenesis in BALB/c Mice · 2026 · DOI

  • The growing awareness regarding the harmful effects of ultraviolet radiation and increasing demand for natural skincare products have created new opportunities for herbal sunscreen development. Recent advances in phytochemical research, nanotechnology, and cosmetic science have highlighted the potential of plant-derived photoprotective agents as safer alternatives to conventional sunscreen ingredients. Future research is expected to focus on improving formulation stability, enhancing SPF performance, increasing clinical validation, and developing environmentally sustainable sunscreen systems. These developments may contribute significantly to the commercialization and global acceptance of herbal sunscreen products.[15,19,24]  Nano-herbal sunscreen system a. Nano-herbal sunscreen systems represent one of the most promising advances in herbal photoprotection. The incorporation of medicinal plant extracts into nanoemulsions, nanoparticles, liposomes, and other nano-carrier systems can significantly improve the stability, bioavailability, and skin penetration of phytochemicals. These delivery systems protect sensitive bioactive compounds from degradation caused by environmental factors such as light, oxygen, and temperature, thereby maintaining their photoprotective activity for longer durations.[16,57,61,62,63] b. Nano-sized carriers also enhance the solubility and controlled release of antioxidant compounds such as flavonoids and polyphenols. Improved retention of these phytochemicals on the skin surface contributes to enhanced SPF values, prolonged antioxidant protection, and better photostability. In addition, nano-herbal formulations may improve cosmetic acceptability by reducing greasiness and providing a more uniform protective layer on the skin.[16,57,61,62,63] c. With continued advancements in nanotechnology, future herbal sunscreen formulations are expected to combine natural phytochemicals with sophisticated nano-delivery systems www.wjpr.net │ Vol 15, Issue 13, 2026. │ ISO 9001: 2015 Certified Journal │ 493 Simran et al. World Journal of Pharmaceutical Research to achieve superior efficacy, safety, and consumer acceptance.[16,57,61,62,63]  Combination herbal SPF boosters a. The use of combination herbal systems is another promising strategy for enhancing sunscreen efficacy. Medicinal plants contain diverse bioactive compounds that often exhibit complementary biological activities. Combining multiple plant extracts rich in flavonoids, phenolic compounds, and polyphenols may result in synergistic antioxidant and photoprotective effects.

    A REVIEW ON HERBAL SUNSCREEN POTENTIAL OF TULSI (OCIMUM SANCTUM) & DURVA (CYNODON DACTYLON) · 2026 · DOI

  • to make(Schalka, de Paula Corrêa et al. 2019). Fourth, although oral antioxidants ( Polypodium carotenoids) have leucotomos extract and potential to systemically protect against photolysis, there is limited direct evidence related to their efficacy in protecting against HEVL specifically, and standardised dosing measures are still deficient in this area(Jo, Jung et al. 2020). 7.4.

    IMPACT OF HIGH-ENERGY VISIBLE (BLUE) LIGHT ON SKIN PIGMENTATION AND MELANOGENESIS: A COMPREHENSIVE REVIEW OF TREATMENT, PREVENTION, AND EMERGING PROTECTIVE INTERVENTIONS · 2026 · DOI

  • Nevertheless, significant challenges still exist - specifically the fact that there are no standardised HEVL testing guidelines, that BPF labelling is not regulated, and not all clinical trials are designed.

    IMPACT OF HIGH-ENERGY VISIBLE (BLUE) LIGHT ON SKIN PIGMENTATION AND MELANOGENESIS: A COMPREHENSIVE REVIEW OF TREATMENT, PREVENTION, AND EMERGING PROTECTIVE INTERVENTIONS · 2026 · DOI

  • Several limitations of this study should be acknowledged. First, the relatively small sample size may limit the statistical power and generalizability of the findings. A larger experimental group would provide more robust evidence regarding the observed anti-aging effects. Second, the primary endpoint was based on macroscopic wrinkle scoring, which, although practical, may be subject to observational variability. The inclusion of histological analysis or quantitative skin elasticity measurements would provide more objective confirmation of dermal structural changes. Third, the study did not incorporate blinding procedures or biomarker assessments such as collagen density, matrix metalloproteinase (MMP) activity, or oxidative stress markers. The absence of these molecular parameters limits mechanistic interpretation of the observed improvements. Finally, although UV-B exposure was administered to induce photoaging, the exact cumulative UV dose absorbed by the skin was not quantitatively measured. Variability in irradiation intensity or exposure uniformity may influence the degree of skin damage and treatment response. Future studies should include standardized dosimetry to improve experimental precision.

    Formulation and Anti-Aging Activity of Collagen Extract from Yellowfin Tuna (Thunnus albacares) Skin Cream in UV-B Induced Wistar Rats · 2026 · DOI

  • Although UVR effects on skin are well described, it is not fully understood how the skin microbiota, an important modulator of skin immunity and barrier integrity, regulates the human cutaneous response to UVR exposure.

    O7 Skin microbiota promotes keratinocyte apoptosis and suppresses proliferation following ultraviolet radiation exposure in human skin <i>in vivo</i> · 2026 · DOI

  • Because UVA radiation lacks a clear, easily observable endpoint comparable to UVB-induced sunburn (erythema), a standardized metric for quantifying UVA protection has not been established in the U.

    Sunscreens: Limitations of Past and Current UVA Protection Metrics in an Era of Rising UVA-Driven Skin Cancers · 2026 · DOI

  • Future research should focus on longitudinal studies, the development of context-appropriate protective technologies, and policy frameworks that reflect the needs of outdoor workers in high- solar ultraviolet radiation (UVR) environments.

    Effects of solar ultraviolet (UV) radiation on outdoor workers health: A systematic literature review · 2026 · DOI

  • While evidence regarding melanoma risk remains inconclusive, observed associations with specific subtypes such as lentigo maligna suggest solar ultraviolet radiation (UVR) may contribute to carcinogenesis through mechanisms that warrant further investigation.

    Effects of solar ultraviolet (UV) radiation on outdoor workers health: A systematic literature review · 2026 · DOI

  • Despite increasing interest, the current evidence base for biological photoprotection remains limited. Most available clinical studies are small and short in duration, which restricts statisti‑ cal power and limits generalizability to broader populations and long‑term outcomes. In addition, many studies rely on surrogate or intermediate endpoints, such as markers of oxidative stress, pigmentation indices, or molec‑ ular indicators of DNA damage. While these endpoints are mechanistically relevant, their relationship to clinically meaningful outcomes, including prevention of photoaging or skin can‑ cer, remains incompletely established. Evidence supporting protection against non‑ UV components of solar radiation and other exposome factors is particularly limited and often derived from in vitro or ex vivo studies rather than robust in vivo clinical trials. Fur‑ thermore, heterogeneity in formulation design, ingredient concentration, and delivery sys‑ tems complicates cross‑study comparison and interpretation. These limitations underscore the need for cautious interpretation of current findings and support the positioning of biological photopro‑ tection as a complementary, rather than substi‑ tutive, approach to established strategies. The combination of PINGs with UV filters also raises several unresolved safety considera‑ tions. Many biologically active compounds are designed to penetrate the skin, whereas UV fil‑ ters are intended to remain at the surface. Co‑ formulation may therefore alter the dermal absorption profile of UV filters. CONCLUSIONS Biological photoprotection represents a concep‑ tual extension of conventional photoprotec‑ tion by addressing biological responses to solar and environmental exposure. Current evidence Dermatol Ther (Heidelb) supports its potential to complement UV fil‑ ters; however, it remains largely preliminary. Accordingly, biological photoprotection should be interpreted as a promising but still evolv‑ ing approach. Broader integration into clini‑ cal practice will require standardized method‑ ologies, harmonized biological endpoints, and well‑designed studies demonstrating clinically relevant benefits under real‑world conditions. ACKNOWLEDGEMENTS The authors thank Blanca Martínez‑Teipel for her valuable scientific discussions. Author Contributions. Anthony Brown: conceptualization, data curation, formal analy‑ sis, investigation, methodology, visualization, writing—original draft, and writing—review and editing. Thierry Passeron: investigation, formal analysis, and writing—review and edit‑ ing. Yolanda Gilaberte: investigation, formal analysis, and writing—review and editing. Jaime Piquero‑Casals: investigation, formal analysis, and writing—review and editing. Ser‑ gio Schalka: investigation, formal analysis, and writing—review and editing. Carla Simonetto: project administration and writing—review and editing. Monica Foyaca: resources, project administration, and writing—review and edit‑ ing. Henry W. Lim: conceptualization, formal analysis, and writing—review and editing. Jean Krutmann: conceptualization, formal analysis, and writing—review and editing. Funding. Sponsorship for this review and Rapid Service Fee were funded by ISDIN, Spain. Data Availability. Data sharing is not applicable to this article as no datasets were generated or analyzed during the current study.

    Biological Photoprotection: A Review of its Mechanisms, Evidence, and Clinical Implications · 2026 · DOI

  • Most reviewed studies on cutaneous aging mechanisms are observational or experimental in animal models, with randomized controlled trials still limited. Clinical translation of findings regarding cGAS-STING pathway activation in photoaging and Langerhans cell dysfunction requires robust human clinical trial data.

    ENVELHECIMENTO CUTÂNEO E INFLAMAÇÃO CRÔNICA DE BAIXO GRAU: O PAPEL DA IMUNOSSENESCÊNCIA NA DERMATOLOGIA CLÍNICA · 2026 · DOI

  • The heterogeneity of the elderly population, with variability in comorbidities, cumulative environmental exposure, genetic factors, and lifestyle, limits generalization of cutaneous immunosenescence findings. Stratified studies accounting for these variables are needed to develop universally applicable therapeutic strategies for geriatric dermatology.

    ENVELHECIMENTO CUTÂNEO E INFLAMAÇÃO CRÔNICA DE BAIXO GRAU: O PAPEL DA IMUNOSSENESCÊNCIA NA DERMATOLOGIA CLÍNICA · 2026 · DOI

  • Combined intervention approaches targeting multiple mechanisms of cutaneous inflammaging simultaneously have not been systematically investigated. Future research must examine combination therapies that simultaneously address macrophage M1/M2 imbalance, senescent cell accumulation, and IL-17 pathway dysregulation in aged skin.

    ENVELHECIMENTO CUTÂNEO E INFLAMAÇÃO CRÔNICA DE BAIXO GRAU: O PAPEL DA IMUNOSSENESCÊNCIA NA DERMATOLOGIA CLÍNICA · 2026 · DOI

  • Predictive biomarkers for stratifying risk of cutaneous immunosenescence and enabling therapeutic personalization in elderly populations have not been identified. Research must focus on identifying specific biomarkers of cutaneous immunosenescence that allow risk stratification and personalized treatment approaches.

    ENVELHECIMENTO CUTÂNEO E INFLAMAÇÃO CRÔNICA DE BAIXO GRAU: O PAPEL DA IMUNOSSENESCÊNCIA NA DERMATOLOGIA CLÍNICA · 2026 · DOI

  • Robust randomized controlled clinical trials of p38 MAPK inhibitors, IL-17 blockers, and senolytic agents for modulating cutaneous inflammaging are lacking. While preclinical studies demonstrate encouraging results, clinical trials establishing safety and efficacy of senolytic drugs in geriatric dermatology remain necessary.

    ENVELHECIMENTO CUTÂNEO E INFLAMAÇÃO CRÔNICA DE BAIXO GRAU: O PAPEL DA IMUNOSSENESCÊNCIA NA DERMATOLOGIA CLÍNICA · 2026 · DOI

  • Sex-related differences in cutaneous inflammaging mechanisms and immunosenescence remain subexplored. Although evidence suggests that sex hormones modulate inflammatory responses and immune function, specific studies investigating sexual dimorphism in cutaneous aging are limited and need targeted investigation.

    ENVELHECIMENTO CUTÂNEO E INFLAMAÇÃO CRÔNICA DE BAIXO GRAU: O PAPEL DA IMUNOSSENESCÊNCIA NA DERMATOLOGIA CLÍNICA · 2026 · DOI

  • The correlation between cutaneous immunosenescence and systemic immunosenescence within individual elderly patients remains incompletely understood. Studies investigating whether skin immunosenescence and systemic immunosenescence are correlated within individuals are necessary to elucidate if skin can serve as an accessible biomarker of systemic immunological aging.

    ENVELHECIMENTO CUTÂNEO E INFLAMAÇÃO CRÔNICA DE BAIXO GRAU: O PAPEL DA IMUNOSSENESCÊNCIA NA DERMATOLOGIA CLÍNICA · 2026 · DOI

  • HAUT scores use an inverse convention for many traits (higher scores = better skin quality = less severe phenotype), requiring careful biological interpretation of effect direction that accounts for this scoring system.

    Skin DNA Methylation Encodes Multidimensional Facial Aging Phenotypes with Distinct Biological Architectures · 2026 · DOI

  • Lambda values substantially greater than 1.0 can indicate either genuine epigenome-wide signal or systematic bias such as residual population stratification, uncorrected batch effects, or incomplete adjustment for confounders, requiring distinction via QQ plots.

    Skin DNA Methylation Encodes Multidimensional Facial Aging Phenotypes with Distinct Biological Architectures · 2026 · DOI

  • This study presents several limitations that warrant consideration. The formulated mangrove leaf extract cream exhibited a dark green coloration, which may reduce its aesthetic acceptability when applied to the skin. Therefore, further reformulation is required to obtain preparation with more acceptable visual characteristics. In addition, the SPF value in this study was assessed solely through in vitro testing, and thus its in vivo photoprotective efficacy has not yet been established. Moreover, advanced molecular analyses are necessary to elucidate the mechanistic effects of the mangrove leaf extract cream on UVB-exposed guinea pig skin, particularly regarding its potential role in modulating collagen synthesis, antioxidant pathways, and cellular responses to UVB-induced oxidative stress.

    Anti-Aging Efficacy of Mangrove Leaf Extract Cream Assessed by SPF and Collagen Density Enhancement: In Vitro and In Vivo Approaches · 2026 · DOI

  • Furthermore, it highlights the complexity and uncertainties in the relationship between climate change and skin cancer and the need for further research on this relationship, including primary epidemiological research and reviews that follow recognised review guidelines and include assessment of health services and social determinants in the causal pathways of this relationship.

    Relationship between climate change and skin cancer and implications for prevention and management: a scoping review · 2024 · DOI

  • The insensitivity of the murine inflammasome sensor NLRP1 to regulation by p3817 did not allow us to capture the full effects of UVB-induced RSR signaling in human skin. The contribution of SLFN11-associated tRNA cleavage to UVB-induced ZAKa activation and cell death is small in HAP1 cells (Figure 6K). Although these cells appear to express higher SLFN11 levels than primary keratinocytes, this effect may be negligible in skin keratinocytes.

    The ribotoxic stress response drives acute inflammation, cell death, and epidermal thickening in UV-irradiated skin in vivo · 2024 · DOI

  • The interaction mechanisms between estrogen hormones (marked as mutagenic agents) and UVB radiation-induced DNA damage require more detailed investigation beyond the current assessment.

    Hormone treatment and UVB exposure influences on female mice regarding skin physiological parameters, biochemical parameters and organ histology · 2021 · DOI

  • Histological changes were observed in internal organs for EES and LNG-treated groups exposed to UVB radiation, but the mechanisms underlying these changes and their long-term implications need further elucidation.

    Hormone treatment and UVB exposure influences on female mice regarding skin physiological parameters, biochemical parameters and organ histology · 2021 · DOI

  • Through further study of spectrophotometry and computerized color formulation, and with the development of pigment databases appropriate for the African-Canadian population, it may be possible to establish a precise and repeatable color matching system that predicts required colorants and controls metamerism.

    Computerized Color Formulation for African‐Canadian People Requiring Facial Prostheses: A Pilot Study · 2008 · DOI

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51 open questions have been extracted from the limitations and future-work passages of 370 Skin Protection and Aging papers in our library. Each one below links back to the study that raised it, so you can read the original claim in context.

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