The outermost epidermal layer of the skin, the stratum corneum, is not simply a barrier that safeguards skin integrity from external insults and invaders, it is also a delicately integrated interface composed of firm, essentially dead corneocytes and a distinctive lipid matrix. Together, the stratum corneum lipid matrix and sebum lipids derived from sebaceous glands give rise to a remarkably complex but quite unique blend of skin surface lipids that demonstrates tremendous heterogeneity and provides the skin with its indispensable protective coating. The stratum corneum lipid matrix is composed primarily of three major lipid classes: ceramides, non-esterified fatty acids and cholesterol, whereas sebum is a waxy mixture predominantly composed of acylglycerols, wax esters, non-esterified fatty acids, squalene, cholesterol and cholesterol esters. The balance of these skin surface lipids in terms of their relative abundance, composition, molecular organisation and dynamics, and their intricate interactions play a crucial role in the maintenance of healthy skin. For that reason, even minuscule alterations in skin surface lipid properties or overall lipid profile have been implicated in the aetiology of many common skin diseases including atopic dermatitis, psoriasis, xerosis, ichthyosis and acne. Novel lipid-based interventions aimed at correcting the skin surface lipid abnormalities have the potential to repair skin barrier integrity and the symptoms associated with such skin diseases, even though the exact mechanisms of lipid restoration remain elusive.

The inherent acidic nature of the stratum corneum (SC), the so-called “acid mantle”, has a multitude of effects on skin barrier integrity owing to its (patho)physiological role in skin homeostasis, antimicrobial defense, and inflammation. Several salient SC acidifying mechanisms, including the breakdown of FLG (filaggrin) protein, lipid processing, and the activity of the sodium proton pump SLC9A1/NHE1, are indispensable for the structural and functional integrity and cohesion of the SC as they contribute immensely to the origin, generation, maintenance, and overall SC acidification of the skin surface pH (pHss). As many endogenous and exogenous factors can affect the pHss, the pHss can inevitably deviate from its optimum. The elevation of the pHss is often accompanied by abnormalities in SC lipid metabolism and organization, SC cohesion, and SC integrity and is commonly observed in eczema, which is associated with symptoms of dry skin, inflammation, pruritus, and infection. In psoriasis, it seems that the pHss is altered as well; however, in this case, it is likely to be lower than the physiological pHss. Due to the negative effects of an altered pHss in both eczema and psoriasis, it has been suggested to maintain the pHss at physiological levels by utilizing pH-balanced topical cleansers and moisturizers that can improve the skin’s structural and functional integrity by benefiting skin moisturization and the regeneration and organization of the SC barrier. The principal aim of this review is to gather an understanding of the existing research and to stimulate critical thinking and inspire innovative ideas about ‘known unknowns’, considering the origin, intricate nature, and prime role of the pHss in human skin health, as well as the pathogenesis of eczema and psoriasis.

This review provides an overview of the structural and functional features of key phytosphingosine-based ceramides (CERs), notably CER[EOP], CER[NP], and CER[AP], and their role in atopic skin health. Herein, we discuss how these indispensable stratum corneum (SC) lipids maintain skin barrier homeostasis and contribute to the skin’s barrier function in terms of its cohesiveness and resilience. We also consider the usefulness of CER[EOP], CER[NP], and CER[AP] in preserving skin hydration and protecting and/or repairing dry, itchy, or sensitive skin. Next, we explore how and to what extent an imbalance or inadequate amounts of CER[EOP], CER[NP], and CER[AP] contribute to the hallmark characteristics of atopic skin diseases like eczema. Furthermore, we discuss the importance of complementary SC resident lipids such as cholesterol (CHOL) and free fatty acids (FFAs), which are crucial for optimal CER function. Studies have shown that delivering topical CERs in balanced and optimal combination with CHOL and FFAs—while supporting and boosting the endogenous biosynthesis of CERs using ingredients such as niacinamide and lactic acid—helps relieve symptoms of atopic diseases to provide some measure of relief. Finally, we look at some emerging ingredients that can complement the science of CERs in healthy and diseased skin.

The skin serves as a primary defensive barrier to protect the body from environmental contaminants, infections and trauma. Unfortunately, skin barrier’s structural and functional integrity can be compromised, disrupted or impaired due to a combination of internal and external factors, making it vulnerable and often leading to a wide range of skin conditions characterized by dryness, heightened sensitivity, and increased susceptibility to damage and infections. In addition, the integrity of the skin barrier tends to deteriorate progressively with age. As people age, their skin naturally changes and can also be compromised by a plethora of factors that reduce its strength and resilience. The aging skin becomes thinner and more sensitive, coinciding with a variety of structural–functional alterations, decreased levels of natural moisturizing factor (NMF), lipid content and hydration, increased transepidermal water loss (TEWL), altered skin surface pH (pHss) and microbiome diversity. All these age-related skin integrity alterations make the skin drier, flakier, itchy, and fragile, and more susceptible to damage and breakdown, thus diminishing its ability to effectively protect, repair and heal efficiently. Identifying skin integrity issues before they progress will foster positive outcomes through effective preventive measures. Hence, it is important to understand the impact of skincare formulations on skin integrity in compromised aging skin. A well-considered, evidence-based approach to skincare can provide cleansing, moisturizing and protective benefits, while aiding the reduction in skin integrity issues like dry and itchy skin, sensitive skin, bruising, skin tears, pressure injuries (PIs), lower leg ulcers and moisture-associated skin damage (MASD). Managing skin integrity in compromised aging skin begins with gentle skin cleansing, adequate moisturization and protective barrier care to ensure the skin’s function is maximized.

Background and Objective: Age-related skin changes affect the skin’s structural and functional integrity and reduce the ability of the skin to perform its key barrier functions. Skin breakdown associated with dryness and itch becomes very common and older individuals are at an increasing risk. We aimed to evaluate a daily cleansing–moisturizing routine and conduct a skin assessment for the presence of five underlying skin integrity parameters among aged-care residents. Methods: This small, 6-week evaluation study included four participants over 80 years of age, all of whom were residents at OLC Care, Rocky Point Residence, Beverley Park, NSW, Australia. Skin assessment for the presence of five underlying clinical parameters including itchy skin, dry skin, bruising, skin tears and pressure injuries was conducted for all four participants at baseline and during the evaluation period. Clinical notes were also taken at baseline, during the evaluation and at the post-evaluation. Furthermore, clinical photographs were taken at baseline and after 2–3 weeks of the cleansing–moisturizing routine. Results: Of the four aged-care residents who participated in this evaluation study, all four showed overall improvement in the appearance of the skin with a reduction in severity of the five underlying skin integrity parameters, including itchy skin, dry skin, bruising, skin tears and pressure injuries, where present. Discussion and Conclusions: This case study has produced basic evidence to support a daily cleansing–moisturizing routine (comprising QV cleansers and moisturizers, and/or a protective barrier cream) as it provides moisturizing and protective benefits to the delicate and fragile skin of aged-care residents, where the aim is to reduce skin integrity associated issues.