Impact of Water Exposure and Temperature Changes on Skin Barrier Function

Fluctuations in equine cutaneous pH and transepidermal water loss with time of day and ambient conditions

Cutaneous pH and transepidermal water loss (TEWL) are commonly utilized measures in dermatological research as they provide information concerning barrier function. The importance of dermal health has become more evident in recent years. Accordingly, the aim of this work was to identify natural fluctuations in the biophysical parameters of healthy equine skin. Cutaneous pH and TEWL was collected on nine mares at 6:00 AM, 12:00 PM, and 6:00 PM daily for five days on the nose, withers, girth area, mid-back, and base of tail. Ambient temperature and humidity were measured at each collection. Statistical analysis was completed using SAS On Demand. Tests included repeated measures, ANOVA, and regression analysis. Mean cutaneous pH significantly differed by day (P = 0.0052) and time (P = 0.0073) but was unaffected by anatomical location (P = 0.2841). Interestingly, cutaneous pH had a significant interaction of day and location (P = 0.0004). Mean TEWL measures significantly differed by day (P < 0.0001), time (P < 0.0001), and anatomical location (P = 0.0231). Interaction of day and time had a significant effect on TEWL (P < 0.0001) and also resulted in a three-way interaction of day, time, and location (P = 0.0167). There were no significant associations of pH with temperature and humidity. All measures of TEWL across all locations were significantly correlated with temperature and humidity (P < 0.0001). Cutaneous pH and TEWL measures are affected by environmental conditions which should be considered in future models and work using dermal characteristics of horses.

Exploring the Complexities of Atopic Dermatitis: Pathophysiological Mechanisms and Therapeutic Approaches

Atopic dermatitis (AD) is a prevalent inflammatory skin condition impacting both children and adults globally, with a prevalence of 15-30%. It ranks as the most prevalent skin disorder based on disability-adjusted life-years by the World Health Organization. It presents with symptoms like skin irritation, redness, dryness, itchiness, and vesicular blisters and commonly coexists with other atopic symptoms like allergic rhinitis, asthma, and food allergies. The pathophysiology involves a complex interplay of genetic predispositions, immunological dysfunctions, and environmental factors leading to tissue inflammation and disrupted skin barrier integrity. Alopecia areata is characterized by nonscarring hair loss and shares correlations with AD including a higher prevalence of atopic diseases, shared intracellular mechanisms involving the JAK-STAT pathway, and potential treatment overlap such as dupilumab. These correlations could direct new areas of research and increased insight for both diseases. Treatment of AD requires a personalized approach due to its complex, multifactorial nature integrating nonpharmacological interventions like skin hydration and trigger avoidance as well as topical and systemic approaches, if necessary, with topical corticosteroids being the first line for flares; long term corticosteroid use poses risk for adverse effects like skin atrophy. Severe cases may require systemic treatments or phototherapy. Future treatment prospects include targeting the dysbiotic microbiome and identifying biomarkers for tailored therapeutic strategies, emphasizing the importance of personalized medicine in optimizing AD management.

Harvesting and manipulating sweat and interstitial fluid in microfluidic devices

Microfluidic devices began to be used to facilitate sweat and interstitial fluid (ISF) sensing in the mid-2010s. Since then, numerous prototypes involving microfluidics have been developed in different form factors for sensing biomarkers found in these fluids under in vitro, ex vivo, and in vivo (on-body) settings. These devices transport and manipulate biofluids using microfluidic channels composed of silicone, polymer, paper, or fiber. Fluid flow transport and sample management can be achieved by controlling the flow rate, surface morphology of the channel, and rate of fluid evaporation. Although many devices have been developed for estimating sweat rate, electrolyte, and metabolite levels, only a handful have been able to proceed beyond laboratory testing and reach the stage of clinical trials and commercialization. To further this technology, this review reports on the utilization of microfluidics towards sweat and ISF management and transport. The review is distinguished from other recent reviews by focusing on microfluidic principles of sweat and ISF generation, transport, extraction, and management. Challenges and prospects are highlighted, with a discussion on how to transition such prototypes towards personalized healthcare monitoring systems.

Filaggrin and beyond: New insights into the skin barrier in atopic dermatitis and allergic diseases, from genetics to therapeutic perspectives

Atopic dermatitis (AD) is the most common inflammatory skin disease worldwide, affecting 20% of children and 5% of adults. One critical component in the pathophysiology of AD is the epidermal skin barrier, with its outermost layer, the stratum corneum (SC), conferring biochemical properties that enable resilience against environmental threats and maintain homeostasis. The skin barrier may be conceptualized as a key facilitator of complex interactions between genetics, host immunity, the cutaneous microbiome, and environmental exposures. The key genetic risk factor for AD development and persistence is a loss-of-function mutation in FLG, with recent advances in genomics focusing on rare variant discovery, establishment of pathogenic mechanisms, and exploration of the role of other epidermal differentiation complex gene variants in AD. Aberrant type 2 inflammatory responses down-regulate the transcription of key epidermal barrier genes, alter the composition of SC lipids, and induce further injury through a neurocutaneous feedback loop and the itch-scratch cycle. The dysbiotic epidermis exhibits reduced bacterial diversity and enhanced colonization with Staphylococcus and Malassezia species, which contribute to both direct barrier injury through the action of bacterial toxins and perpetuation of the inflammatory cascades. Enhanced understanding of each of the pathogenic mechanisms underpinning barrier disruption has led to the development of novel topical and systemic molecules, including interleukin (IL)-4Ra, IL-13, PDE4, and Janus-associated kinase inhibitors, whose clinical effectiveness exceeds conventional treatment modalities. In this narrative review, we aim to summarize the current understanding of the above-mentioned pathophysiological and therapeutic mechanisms, with a focus on the genetic, cellular, and molecular mechanisms underpinning AD development.

Bathing in Atopic Dermatitis in Pediatric Age: Why, How and When

Atopic dermatitis is a chronic inflammatory skin disease. The treatment plays an important role in influencing the patients' quality of life. The basic management consists of appropriate skin cleansing, including bathing and eventually using bathing additives. Recommendations regarding frequency and duration of bathing, water temperature and usefulness of bathing additives are widely different, often leading to confusion among patients. This review aims to give insights into the best bathing practices and the use of bathing additives in atopic dermatitis in children. Several bathing additives, including bleach baths, commercial baby cleansers, bath baby oils and bath salt, appear to be promising adjunctive therapies for atopic dermatitis due to their anti-inflammatory, anti-bacterial, anti-pruritus and skin barrier repair properties through different mechanisms of action. However, their efficacy and safety are not fully understood in some cases. The usefulness of other bath additives, such as acidic and more natural substances (green tea extracts, pine tar, sodium bicarbonate), is still under investigation. Further studies are needed to determine their optimal use to achieve clinical benefit safely.

Access and Management of Sweat for Non-Invasive Biomarker Monitoring: A Comprehensive Review

Sweat is an important biofluid presents in the body since it regulates the internal body temperature, and it is relatively easy to access on the skin unlike other biofluids and contains several biomarkers that are also present in the blood. Although sweat sensing devices have recently displayed tremendous progress, most of the emerging devices primarily focus on the sensor development, integration with electronics, wearability, and data from in vitro studies and short-term on-body trials during exercise. To further the advances in sweat sensing technology, this review aims to present a comprehensive report on the approaches to access and manage sweat from the skin toward improved sweat collection and sensing. It is begun by delineating the sweat secretion mechanism through the skin, and the historical perspective of sweat, followed by a detailed discussion on the mechanisms governing sweat generation and management on the skin. It is concluded by presenting the advanced applications of sweat sensing, supported by a discussion of robust, extended-operation epidermal wearable devices aiming to strengthen personalized healthcare monitoring systems.

The effects of fucoidan-rich polysaccharides extracted from Sargassum horneri on enhancing collagen-related skin barrier function as a potential cosmetic product

BACKGROUND

Sargassum horneri came ashore after flowing from the South China Sea to Jeju Island a few years ago. This caused a significant environmental impact on coastal areas where S. horneri has accumulated because of decomposition and the release of toxic substances, such as hydrogen sulfide.

AIMS

In this study, we evaluated a biological ingredient prepared from fucoidan-rich S. horneri and demonstrated its antiwrinkle effects on ultraviolet B (UVB)-induced fibroblast cells.

MATERIALS AND METHODS

Fucoidan samples from S. horneri were prepared according to a previously published process with modifications. The compositional analysis of S. horneri fucoidan extract (SHFE) as well as its effects on antiaging were examined to determine its utility as a functional material.

RESULTS

SHFE exhibited antioxidant properties using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. Treatment of UVB-induced fibroblasts with SHFE significantly increased the synthesis of procollagen compared with adenosine treatment and inhibited MMP-1 and MMP-3 expression. In a clinical study, SHFE lotion improved skin barrier effects in forearms and transepidermal water loss (TEWL) values were reduced after 3 weeks of use compared with a placebo.

CONCLUSION

SHFE has utility as an additive with functional antiaging effects for a range of cosmetic products as it restores skin hydration in the epidermal barrier.

Pooling the evidence: A review of swimming and atopic dermatitis

Swimming is an excellent form of aerobic exercise and is an essential life skill. Many children with atopic dermatitis (AD) are advised not to swim because of concerns about negative impacts on their skin disease, and some children with AD do not swim because they are self-conscious about the appearance of their skin. We aimed to perform a narrative review of the available literature on swimming and AD and scientifically analyze the potential impact of all components of swimming in AD-water, skin barrier, swimming gear, and exercise. Studies examined the impact of swimming on the skin barrier and the relative contraindications to swimming. Constituents of water which may affect AD include hardness, pH, temperature, antiseptics, and other chemicals. Potential interventions to reduce damage included emollient application, special swim gear, and showering post-submersion. The benefits of swimming as a form of exercise in AD included reduced sweating, cardiorespiratory fitness, and maintenance of healthy weight. Drawbacks of swimming as a form of exercise in AD included the limited benefit on bone mineral density. Future research should examine the impact of swimming on flares of AD using noninvasive biomarkers as well as clinical severity assessment and assess the role for different types of emollient as an intervention for optimal eczema control. This review highlights gaps in the scientific literature on swimming and AD and provides evidence-based guidance on interventions to minimize deleterious effects on skincare and maximize opportunities for children with AD to swim.

Directional assessment of the skin barrier function in vivo

INTRODUCTION

The fundamental function of the epidermis is to provide an inside-out barrier to water loss and an outside-in barrier to penetration of external irritants. Transepidermal water loss (TEWL) has been extensively used as a method of estimating the skin barrier quality, typically without any consideration of directionality. The validity of TEWL as an estimate of skin permeability to external substances has been controversial in vitro and in vivo. The aim of this work was to assess the relationship between TEWL and the penetration of a topically applied external marker (caffeine) in healthy skin in vivo before and following a challenge to the barrier.

METHODS

The skin barrier was challenged by application of aqueous solutions of mild cleanser products under occlusion for 3 h on the forearms of nine human participants. Skin barrier quality was evaluated before and after the challenge by measuring the TEWL rate and the permeated amount of topically applied caffeine using in vivo confocal Raman microspectroscopy.

RESULTS

No skin irritation was observed following the skin barrier challenge. TEWL rates and the caffeine penetrated amount in the stratum corneum after the challenge were not correlated. A weak correlation was observed when the changes were corrected to water-only treatment. TEWL values can be influenced by environmental conditions as well as the skin temperature and water content.

CONCLUSIONS

Measuring TEWL rates is not always representative of the outside-in barrier. TEWL may be useful in differentiating large changes in skin barrier function (e.g., between healthy and compromised skin) but is less sensitive to small variations following topical application of mild cleansers.

The Imprint of Exposome on the Development of Atopic Dermatitis across the Lifespan: A Narrative Review

Atopic dermatitis (AD) is a chronic inflammatory skin condition that affects more than 200 million people worldwide, including up to 20% of children and 10% of the adult population. Although AD appears frequently in childhood and often continues into adulthood, about 1 in 4 adults develop the adult-onset disease. The prenatal period, early childhood, and adolescence are considered critical timepoints for the development of AD when the exposome results in long-lasting effects on the immune system. The exposome can be defined as the measure of all the exposures of an individual during their lifetime and how these exposures relate to well-being. While genetic factors could partially explain AD onset, multiple external environmental exposures (external exposome) in early life are implicated and are equally important for understanding AD manifestation. In this review, we describe the conceptual framework of the exposome and its relevance to AD from conception and across the lifespan. Through a spatiotemporal lens that focuses on the multi-level phenotyping of the environment, we highlight a framework that embraces the dynamic complex nature of exposome and recognizes the influence of additive and interactive environmental exposures. Moreover, we highlight the need to understand the developmental origins of AD from an age-related perspective when studying the effects of the exposome on AD, shifting the research paradigm away from the per se categorized exposome factors and beyond clinical contexts to explore the trajectory of age-related exposome risks and hence future preventive interventions.

Ionic Liquid-Based Transcutaneous Peptide Antitumor Vaccine: Therapeutic Effect in a Mouse Tumor Model

Traditional vaccinations need to be injected with needles, and since some people have a strong aversion to needles, a needle-free alternative delivery system is important. In this study, we employed ionic liquids (ILs) for transcutaneous delivery of cancer antigen-derived peptides to obtain anticancer therapeutic effects in a needle-free manner. ILs successfully increased the in vitro skin permeability of a peptide from Wilms tumor 1 (WT1), one of the more promising cancer antigens, plus or minus an adjuvant, resiquimod (R848), a toll-like receptor 7 agonist. In vivo studies demonstrated that concomitant transcutaneous delivery of WT1 peptide and R848 by ILs induced WT1-specific cytotoxic T lymphocyte (CTL) in mice, resulting in tumor growth inhibition in Lewis lung carcinoma-bearing mice. Interestingly, administrating R848 in ILs before WT1 peptides in ILs increased tumor growth inhibition effects compared to co-administration of both. We found that the prior application of R848 increased the infiltration of leukocytes in the skin and that subsequent delivery of WT1 peptides was more likely to induce WT1-specific CTL. Furthermore, sequential immunization with IL-based formulations was applicable to different types of peptides and cancer models without induction of skin irritation. IL-based transcutaneous delivery of cancer antigen-derived peptides and adjuvants, either alone or together, could be a novel approach to needle-free cancer therapeutic vaccines.

Irritative potential of different washing procedures used for heavy-duty soiling: Short and intense or longer and mild?

BACKGROUND

To prevent irritant contact eczema even in occupational fields with heavy-duty soiling, it is generally recommended to use 'mild' hand cleansers (mild detergent without grits, MC). On the other hand, since grit-containing cleansers (GC) show a higher washing power that minimizes washing time, their usage is generally preferred in specific occupational fields.

OBJECTIVES

To compare whether a shorter, intense washing period might cause less skin damage than a longer washing period with an MC.

METHODS

Differences in cleaning time were first verified in a pilot study using standardized model dirt. In the main study, the forearms of 35 healthy volunteers were washed with three standardized procedures over a period of 3 days, either using 2 min of MC with/without hand brush or 1-min GC. Clinical scoring, transepidermal water loss (TEWL), corneometry, colourimetry and scaliness/roughness (Visioscan) were used to evaluate the epidermal barrier, topography and irritation.

RESULTS

The pre-study showed that washing time doubled when using MC vs. GC. Using GC resulted in stronger barrier disruption, even after a shorter washing period - median ΔT4-T1 TEWL 0.96 g/m² /h vs. 4.91 g/m² /h respectively, p < 0.0001. The most harmful procedure for the skin was the additional application of a hand brush (18.86 g/m² /h).

CONCLUSIONS

Short-time washing with GC damages the skin barrier more significantly in comparison to a longer application of an MC. When washing with MC, the strongest irritant reaction occurred when accompanied with hand brushing.