Background/purpose: Melasma is a frequent photoexacerbated hyperpigmentary disorder, which can significantly impact on the quality of life. We sought to review the pathogenesis of melasma, and the role of photoprotection in the prevention and treatment of this disorder.Methods: We conducted a narrative review of the literature. We performed literature searches with PubMed from January 1990 to December 2021 using the keywords “melasma,” “pathogenesis,” “ultraviolet radiation,” “visible light,” “photoprotection,” and “sunscreens.”Results: The physiopathology of melasma includes a complex interaction between genetics, sex hormones, and sun exposure. Visible light, in particular high‐energy visible light (HEVL), and long‐wave UVA (UVA1) play a key role in melasma pathophysiology, and recent research suggests that melasma shares many features with photoaging disorders. Melasma disproportionately affects dark‐skinned individuals. Some 30% to 50% of South Americans and Asians, among other ethnicities, can present with melasma. Dark‐skinned patients take fewer photoprotective measures. Also, the majority of melasma patients do not adequately follow photoprotection recommendations, including the application of sunscreen. Intensive use of a broad‐spectrum sunscreen can prevent melasma in high‐risk individuals, can lessen melasma severity (associated or not with depigmenting agents), and can reduce relapses.Conclusions: Due to the physiopathology of melasma, sunscreens should be broad‐spectrum with high sun protection factor, and provide high protection against UVA1 and VL. Sunscreens should be cosmetically acceptable and leave no white residue. Tinted sunscreens are an excellent choice, as pigments can protect from HEVL and UVA1, and may provide camouflage, but they must offer colors that match the skin tone of each patient.

Background: Pathophysiology of rosacea is not completely understood and involves a complex interaction among genetics, ultraviolet (UV) light, microorganisms, impaired skin barrier, neuronal and vascular dysfunction, and immune system disruption.Aims: To describe the etiology of rosacea with an emphasis on the role of UV radiation and exposome, and to review the importance of non‐pharmacologic strategies focusing on photoprotection.Methods: We conducted a narrative review of the literature. We performed literature searches with PubMed from January 1990 to November 2020 using the keywords “rosacea”, “pathogenesis”, “ultraviolet radiation”, “exposome”, “photoprotection”, “sunscreens” and “non‐pharmacologic agents”. The search was limited to English, Spanish, and French language articles.Results: Several environmental factors such as UV light, diverse microorganisms, air pollution, tobacco smoking, nutrition, and psychological stress showed to trigger or worsen rosacea. UV radiation was reported to induce pro‐inflammatory, pro‐angiogenic, and pro‐fibrotic responses. We found 6 original articles about the impact of sunscreens on rosacea. The use of sunscreens containing ingredients with emollient, anti‐inflammatory, and/or vasoregulatory properties was shown to significantly improve symptomatology.Conclusion: UV radiation and the exposome play a key role in the development of rosacea. UV light is implicated in all significant aspects of rosacea: skin inflammation, neoangiogenesis, telangiectasia, and fibrosis, and may even initiate rosacea. While the use of sunscreens is widely recommended, the literature on the impact of photoprotection in rosacea is scarce. Adequately formulated sunscreens could not only provide the required level of photoprotection, but may also help to mitigate the barrier dysfunction, neutralize facial redness (tinted sunscreens), and decrease inflammation and vascular dysfunction.

Introduction The risk of infections associated with biological drugs (BD) and Janus kinase inhibitors (JAKi) has been extensively explored in the literature. However, there is a dearth of studies that evaluate both pharmacological groups together and, furthermore, compare them. Here, we review the risk of infections associated with BD and JAKi used in dermatology. Methods A narrative review was performed. All relevant articles evaluating the risk of infection and opportunistic infections with BD and JAKi between January 2010 and February 2024 were selected. Results Overall, the incidence of infections, serious infections, and opportunistic infections associated with BD and JAKi is low, but higher than in the general population. JAKi approved for dermatological disorders (abrocitinib, baricitinib, deucravacitinib, upadacitinib, ritlecitinib, and topical ruxolitinib) have been shown to be safe, and present a low rate of infections. We found an elevated risk, especially with anti-tumor necrosis factor (anti-TNF) agents, rituximab, and JAKi (particularly tofacitinib at high doses). Specific associations with infections include tuberculosis and tuberculosis reactivation with anti-TNF agents and tocilizumab; candidiasis with anti-interleukin (IL) 17 agents; hepatitis B virus reactivation with rituximab, anti-TNF, and JAKi; and herpes simplex and herpes zoster infections with JAKi (especially tofacitinib and upadacitinib at high doses). The incidence of infections with ustekinumab and anti-IL-23 was very low. Anti-IL-1, nemolizumab, tralokinumab, and omalizumab were not associated with an increased risk of infections. Dupilumab could decrease the incidence of cutaneous infections. Conclusions Anti-TNF agents, rituximab, and JAKi (particularly tofacitinib) can increase the risk of infections. Close monitoring of patients undergoing these therapies is recommended. Prospective studies with long-term follow-up are needed to comparatively evaluate the risks of infection deriving from treatment with BD and JAKi.

Background: Acne pathophysiology includes a complex interaction among inflammatory mediators, hyperseborrhea, alteration of keratinization and follicular colonization by Propionibacterium acnes.Aims: To describe the impact of the exposome on acne and how photoprotection can improve outcomes.Methods: A narrative review of the literature was carried out; searches with Google Scholar and Pubmed from January 1992 to November 2022 were performed. The keywords used were “acne,” “sunscreens,” “photoprotection,” “cosmetics,” “cosmeceuticals,” “pathogenesis,” “etiology,” “exposome,” “sunlight,” “stress,” “lack of sleep,” “diet,” “postinflammatory hyperpigmentation,” “pollution,” “exposome,” “ultraviolet radiation,” and “visible light.”Results: Environmental factors such as solar radiation, air pollution, tobacco consumption, psychological stress, diverse microorganisms, nutrition, among others, can trigger or worsen acne. Solar radiation can temporarily improve lesions. However, it can induce proinflammatory and profibrotic responses, and produce post‐inflammatory hyperpigmentation and/or post‐inflammatory erythema. While photoprotection is widely recommended to acne patients, only four relevant studies were found. Sunscreens can significantly improve symptomatology or enhance treatment and can prevent post‐inflammatory hyperpigmentation. Furthermore, they can provide camouflage and improve quality of life. Based on acne pathogenesis, optimal sunscreens should have emollient, antioxidant and sebum controlling properties.Conclusions: The exposome and solar radiation can trigger or worsen acne. UV light can induce post‐inflammatory hyperpigmentation/erythema, and can initiate flares. The use of specifically formulated sunscreens could enhance adherence to topical or systemic therapy, camouflage lesions (tinted sunscreens), decrease inflammation, and reduce the incidence of post‐inflammatory hyperpigmentation/erythema.

Background: Data on the clinical patterns and histopathology of SARS-CoV-2 related skin lesions, as well as on their relationship with the severity of COVID-19 are limited. Methods and Materials: Retrospective analysis of a prospectively collected cohort of patients with SARS-CoV-2 infection in a teaching hospital in Barcelona, Spain, from 1 April to 1 May 2020. Clinical, microbiological and therapeutic characteristics, clinicopathological patterns of skin lesions, and direct immunofluorescence and immunohistochemical findings in skin biopsies were analyzed. Results: Fifty-eight out of the 2761 patients (2.1%) either consulting to the emergency room or admitted to the hospital for COVID-19 suspicion during the study period presented COVID-19 related skin lesions. Cutaneous lesions could be categorized into six patterns represented by the acronym “GROUCH”: Generalized maculo-papular (20.7%), Grover’s disease and other papulo-vesicular eruptions (13.8%), livedo Reticularis (6.9%), Other eruptions (22.4%), Urticarial (6.9%), and CHilblain-like (29.3%). Skin biopsies were performed in 72.4%, including direct immunofluorescence in 71.4% and immunohistochemistry in 28.6%. Patients with chilblain-like lesions exhibited a characteristic histology and were significantly younger and presented lower rates of systemic symptoms, radiological lung infiltrates and analytical abnormalities, and hospital and ICU admission compared to the rest of patients. Conclusion: Cutaneous lesions in patients with COVID-19 appear to be relatively rare and varied. Patients with chilblain-like lesions have a characteristic clinicopathological pattern and a less severe presentation of COVID-19.