Skin pH: from basic science to basic skin care.
TL;DR: Recent basic science investigations into skin pH are reviewed, skin disorders characterized by aberrant pH are discussed, and practical application for preservation of the acid mantle is discussed.
Abstract: The "acid mantle" is a topic not only of historical interest, but also of clinical significance and has recently been linked to vital stratum corneum function. Despite compelling basic science evidence placing skin pH as a key factor in barrier homeostasis, stratum corneum integrity, and antimicrobial defense, application of the acid mantle concept in clinical care is lacking. We review recent basic science investigations into skin pH, discuss skin disorders characterized by aberrant pH, and finally discuss practical application for preservation of the acid mantle. Recognizing factors that alter skin pH and selecting products that preserve the acid mantle is of prime importance in treating dermatologic patients.
Citations
More filters
TL;DR: This Journal feature begins with a case vignette highlighting a common clinical problem, followed by a review of formal guidelines, when they exist, and the authors’ clinical recommendations.
Abstract: Copyright © 2013 Massachusetts Medical Society. An otherwise healthy 55-year-old man reports that he has been itchy all over for 6 months. The itch interferes with falling asleep and wakes him repeatedly during the night. Initially, there was no rash, but during the past 4 months, itchy nodules and plaques have developed on his back, arms, and legs. Treatment with sedating and nonsedating oral antihistamines and topical glucocorticoids has had no effect. How would you evaluate and manage this case?
322 citations
TL;DR: This review will focus on the mediators of chronic pruritus mainly associated with atopic dermatitis (atopic itch), as well as numerous different therapeutic options.
Abstract: For centuries, itch was categorized as a submodality of pain. Recent research over the last decade has led to the realization that itch is in fact a separate and distinct, albeit closely related, sensation. Chronic itch is a common complaint and has numerous etiologies. Various receptors (TRPA1, TRPV1, PAR2, gastrin-releasing peptide receptor (GRPR), Mas-related G proteins), secreted molecules (histamine, nerve growth factor (NGF), substance P (SP), proteases), and cytokines/chemokines (thymic stromal lymphopoietin (TSLP), IL-2, IL-4, IL-13, and IL-31) are implicated as mediators of chronic pruritus. While much remains unknown regarding the mechanisms of chronic itch, this much is certain: there is no singular cause of itch. Rather, itch is caused by a complex interface between skin, keratinocytes, cutaneous nerve fibers, pruritogenic molecules, and the peripheral and central nervous systems. Atopic dermatitis is one of the most itchy skin dermatoses and affects millions worldwide. The sensation of atopic itch is mediated by the interplay between epidermal barrier dysfunction, upregulated immune cascades, and the activation of structures in the central nervous system. Clinicians are in possession of an arsenal of different treatment options ranging from moisturizers, topical immunomodulators, topical anesthetic ion channel inhibitors, systemic immunomodulators, as well as oral drugs capable of reducing neural hypersensitization. Emerging targeted therapies on the horizon, such as dupilumab, promise to usher in a new era of highly specific and efficacious treatments. Alternative medicine, stress reduction techniques, and patient education are also important treatment modalities. This review will focus on the mediators of chronic pruritus mainly associated with atopic dermatitis (atopic itch), as well as numerous different therapeutic options.
280 citations
Cites background from "Skin pH: from basic science to basi..."
...Human skin is naturally coated with a very fine slightly acidic film, known as the acid mantle, which acts as barrier to bacteria, allergens, and other environmental threats that might seek to penetrate the skin [266, 267]....
[...]
TL;DR: Normalizing the pH by acidification through topical treatment helps to establish a physiological microbiota, to repair skin barrier, to induce epidermal differentiation and to reduce inflammation.
Abstract: The pH plays an important physiological role in nature and humans. pH varies from 1 to 8 in human organs with tight regulation in blood and epithelia of barrier organs. The physiological pH of the stratum corneum is 4.1-5.8 and several mechanisms contribute to its formation: filaggrin degradation, fatty acid content, sodium-hydrogen exchanger (NHE1) activation and melanosome release. First, the acidic pH of the stratum corneum was considered to present an antimicrobial barrier preventing colonization (e.g. by Staphylococcus aureus and Malassezia). Later on, it was found that the pH influences skin barrier function, lipid synthesis and aggregation, epidermal differentiation and desquamation. Enzymes of ceramide metabolism (e.g. β-glucocerebrosidase or acid sphingomyelinase) as well as proteases (e.g. chymotryptic enzyme or cathepsin D linked to epidermal differentiation and desquamation) are regulated by the pH. Experimental disruption of the physical barrier leads to an increase of pH, returning to normal levels only after many hours. Inflammatory skin diseases and diseases with an involvement of the epidermis exhibit a disturbed skin barrier and an increased pH. This is known for atopic dermatitis, irritant contact dermatitis, ichthyosis, rosacea and acne, but also for aged and dry skin. Normalizing the pH by acidification through topical treatment helps to establish a physiological microbiota, to repair skin barrier, to induce epidermal differentiation and to reduce inflammation.
254 citations
TL;DR: Improved identification and characterization of AD phenotypes and endotypes are required to optimize the precision medicine approach to AD.
Abstract: The epidermis contains epithelial cells, immune cells, and microbes which provides a physical and functional barrier to the protection of human skin. It plays critical roles in preventing environmental allergen penetration into the human body and responsing to microbial pathogens. Atopic dermatitis (AD) is the most common, complex chronic inflammatory skin disease. Skin barrier dysfunction is the initial step in the development of AD. Multiple factors, including immune dysregulation, filaggrin mutations, deficiency of antimicrobial peptides, and skin dysbiosis contribute to skin barrier defects. In the initial phase of AD, treatment with moisturizers improves skin barrier function and prevents the development of AD. With the progression of AD, effective topical and systemic therapies are needed to reduce immune pathway activation and general inflammation. Targeted microbiome therapy is also being developed to correct skin dysbiosis associated with AD. Improved identification and characterization of AD phenotypes and endotypes are required to optimize the precision medicine approach to AD.
198 citations
TL;DR: Primary prophylaxis in children with established AD can be stratified into prevention of disease exacerbations by using proactive approaches (with either topical corticosteroids or topical calcineurin inhibitors) in mild AD cases or the prevention of other atopic disorders that will probably mandate systemic immunosuppression in severe AD cases.
Abstract: Skin barrier abnormalities have been suggested to play an essential role in initiation of early atopic dermatitis (AD) Antigen penetration through a compromised barrier likely leads to increased innate immune responses, antigen-presenting cell stimulation, and priming of overt cutaneous disease In a TH2-promoting environment, T-cell/B-cell interactions occurring in regional lymph nodes lead to excessive IgE switch Concurrent redistribution of memory T cells into the circulation not only leads to exacerbation of AD through T-cell skin infiltration but also spreads beyond the skin to initiate the atopic march, which includes food allergy, asthma, and allergic rhinitis Possible primary interventions to prevent AD are focusing on improving skin barrier integrity, including supplementing barrier function with moisturizers As for secondary prophylaxis in children with established AD, this can be stratified into prevention of disease exacerbations by using proactive approaches (with either topical corticosteroids or topical calcineurin inhibitors) in mild AD cases or the prevention of other atopic disorders that will probably mandate systemic immunosuppression in severe AD cases
187 citations
References
More filters
Book•
01 Jan 1979
TL;DR: A comprehensive and critical review of the medical and scientific literature on Candida infections by a leading authority in the field.
Abstract: A comprehensive and critical review of the medical and scientific literature on Candida infections by a leading authority in the field. Covers all aspects of the subject, including epidemiology, pathogensis and treatment, as well as the properties of the fungi that cause infections.
1,664 citations
TL;DR: Findings suggest that an insufficiency of ceramides in the stratum corneum is an etiologic factor in atopic dry skin.
976 citations
TL;DR: Further elucidation of the molecular architecture and interactions of lipid and nonlipid components of the stratum corneum intercellular domains will be a prerequisite for a comprehensive understanding of stratum Corneum function.
Abstract: Publisher Summary This chapter discusses the structural and lipid biochemical correlates of the epidermal permeability barrier. A pivotal point in terrestrial adaptation is prevention of desiccation and maintenance of internal water homeostasis. The outermost integumentary tissue, the epidermis, maintains a reserve of germinal cell layers whose proliferation, stratification, and differentiation result in the production of the outermost layer, the anucleate stratum corneum. The stratum corneum has heterogeneous tissue structure possessing a selected array of enzymatic activity. The sequestration of lipids to intercellular domains and their organization into a unique multilamellar system have broad implications for permeability barrier function, water retention, desquamation, and percutaneous drug delivery. Yet, the functions and organization of specific lipid species in this membrane system are still unknown. Further, elucidation of the molecular architecture and interactions of lipid and nonlipid components of the stratum corneum intercellular domains will be a prerequisite for a comprehensive understanding of stratum corneum function.
660 citations
TL;DR: In sweat, a proteolytically processed 47–amino acid peptide was generated that showed antimicrobial activity in response to a variety of pathogenic microorganisms, indicating that sweat plays a role in the regulation of human skin flora through the presence of an antimicrobial peptide.
Abstract: Antimicrobial peptides are an important component of the innate response in many species. Here we describe the isolation of the gene Dermcidin, which encodes an antimicrobial peptide that has a broad spectrum of activity and no homology to other known antimicrobial peptides. This protein was specifically and constitutively expressed in the sweat glands, secreted into the sweat and transported to the epidermal surface. In sweat, a proteolytically processed 47–amino acid peptide was generated that showed antimicrobial activity in response to a variety of pathogenic microorganisms. The activity of the peptide was maintained over a broad pH range and in high salt concentrations that resembled the conditions in human sweat. This indicated that sweat plays a role in the regulation of human skin flora through the presence of an antimicrobial peptide. This peptide may help limit infection by potential pathogens in the first few hours following bacterial colonization.
652 citations
TL;DR: Enhanced PAR-2 signaling is identified as a new link between inflammatory and sensory phenomena in atopic dermatitis patients and represents a promising therapeutic target for the treatment of cutaneous neurogenic inflammation and pruritus.
Abstract: We examined whether neuronal proteinase-activated receptor-2 (PAR-2) may be involved in pruritus of human skin. The endogenous PAR-2 agonist tryptase was increased up to fourfold in atopic dermatitis (AD) patients. PAR-2 was markedly enhanced on primary afferent nerve fibers in skin biopsies of AD patients. Intracutaneous injection of endogenous PAR-2 agonists provoked enhanced and prolonged itch when applied intralesionally. Moreover, itch upon mast cell degranulation was abolished by local antihistamines in controls but prevailed in AD patients. Thus, we identified enhanced PAR-2 signaling as a new link between inflammatory and sensory phenomena in AD patients. PAR-2 therefore represents a promising therapeutic target for the treatment of cutaneous neurogenic inflammation and pruritus.
579 citations