The acid mantle concept refers to the buffer system located in the upper stratum corneum of the skin. By sustaining an acidic environment, the acid mantle contributes to the regulation of the microbiome, structural stability, and inflammation. Skin pH is pivotal in maintaining the integrity of the epidermal barrier. Shifts in pH can disrupt barrier properties, and recent studies have emphasized its impact on dermatologic disease processes. This review explores the complex relationship of mechanisms through which skin pH impacts dermatologic pathologies. Furthermore, we highlight the promising potential of pH-targeted therapies for advancing the management of skin conditions.

BACKGROUND: Skincare and makeup \"pilling\" is an unsightly and undesirable phenomenon whereby skincare such as moisturizers or foundation ball up to form flakes on the skin. To date, the causes of skincare product pilling have not been studied. This study aimed to examine the relationship between skin physiology and pilling potential of sunscreen and foundation (the two products most reported by consumers to cause pilling). This study also examined the effects of product application methods on pilling.
METHODS: 528 female volunteers from Guangzhou, China, aged between 20 and 49 years, underwent various clinical skin assessments, followed by three steps of product layering. Pilling was assessed after each product application step.
RESULTS: 217 volunteers (41%) experienced pilling. The majority of pilling (n = 655 events) occurred following sunscreen application, while only a few pilling events (n = 35) occurred with foundation. Foundation improved pilling caused by sunscreen in 98.9% of cases. Volunteers experiencing pilling with both sunscreen and foundation had significantly lower facial skin hydration and oiliness, higher pH, and smoother skin texture (P < 0.05). Two application methods, rubbing of products in circular and linear motions, yielded the highest numbers of pilling events.
CONCLUSIONS: This study has provided the first insights into the causes of pilling. Sunscreen is a promoter of pilling, while foundation may resolve sunscreen-induced pilling in many cases. Skin physiology, particularly drier, smoother skin with higher pH, and product application methods are likely contributing factors to this undesirable phenomenon.

UNASSIGNED: Overweight and obesity have become public health problems worldwide. An increasing number of research works are focusing on skin physiology and the manifestations of obesity-associated skin diseases, but little is known about the correlations between body mass index (BMI), facial skin physiological parameters, and the facial skin microbiome in healthy women.
UNASSIGNED: To investigate the correlations between BMI, facial skin physiological parameters and facial bacteria and fungi in 198 women aged 18 to 35 years in Shanghai.
UNASSIGNED: According to the international BMI standard and Chinese reference standard, subjects were divided into three groups, \"lean\" B1, \"normal\" B2 and \"overweight\" B3, and the physiological parameters of facial skin were measured by non-invasive instrumental methods, and the skin microbiota was analyzed by 16S rRNA and ITS high-throughput sequencing.
UNASSIGNED: Compared with the skin physiological parameters of the normal group, those of the overweight group exhibited a significant increase in trans-epidermal water loss (TEWL), which indicated that the skin barrier was impaired. The skin haemoglobin content was significantly increased, and skin surface pH was significant decreased in those with a high BMI. Furthermore, α-diversity, analysed using the Shannon, Chao, Sobs, and Ace indexes, was increased in the overweight group, suggesting that the diversity and species abundance of facial bacterial and fungal microbiota were also increased. Moreover, the overweight group had higher abundances of Streptococcus, Corynebacterium, Malassezia, and Candida. Notably, skin surface pH was significantly and negatively correlated with the relative abundances of Malassezia, Candida, and Cladosporium. Besides, the abundance of Malassezia was positively associated with the abundances of Staphylococcus and Corynebacterium.
UNASSIGNED: These results indicate that BMI is associated with differences in the biophysical properties and microbiome of the facial skin. A high BMI affects the integrity of skin barrier and changes the skin flora diversity and species composition.

UNASSIGNED: The skin has evolved a system to prevent pathogenic microorganism colonization and infection. This study examined the role of natural moisturizing factors (NMFs) and skin pH on Staphylococcus aureus (S. aureus) growth and colonization on the human stratum corneum (SC).
UNASSIGNED: A survey study with 82 female participants was performed. Participants maintained their daily hygiene routine, except for refraining from using leave-on products on their forearms on the day of the test. Skin sampling was performed using adhesive tapes. An ex vivo method was developed to study the viability and growth of S. aureus on human SC sampled from normal skin. NMFs, including pyrrolidone carboxylic acid (PCA), urocanic acid (UCA), histidine, and proline in SC samples, were measured by liquid chromatography with tandem mass spectrometry. The impact of PCA and UCA on S. aureus growth and metabolic activity was measured by optical density and isothermal microcalorimetry, respectively.
UNASSIGNED: Heterogeneity of S. aureus viability on human SC samples was observed. Skin pH showed a significant negative association (p<0.05) with SC antibacterial activity in the ex vivo assay. One unit of skin pH decrease corresponded to 68.1% of S. aureus cell death. The levels of PCA and histidine were significantly negatively associated (p<0.05) with skin pH. The addition of 5 mM and 10 mM PCA significantly inhibited S. aureus growth by approximately 25% at 20 hours and reduced its metabolic activity in vitro.
UNASSIGNED: The results indicate that PCA, one of the NMFs in human skin, plays an important role in regulating the human skin acid mantle in vivo and contributes to antibacterial activity against S. aureus.

UNASSIGNED: Various diagnostic tools are used to assess cutaneous psoriasis, but most of it were subjective. Sympathetic skin response (SSR), skin PH and temperature objectively measure the skin barrier functions that could aid clinicians to evaluate accurately and predict skin disease incidence even before the onset of clinical symptoms.
UNASSIGNED: The study\'s objective was to assess the utility of cutaneous parameters (skin temperature and pH) and SSRs influencing psoriatic patients\' diagnosis management and treatment compared to controls.
UNASSIGNED: A total of 40 healthy participants and 40 psoriasis patients aged 18 to 65 years were recruited for this study. SSR, skin temperature and pH were assessed. The psoriasis disability index (PDI) was recorded from all the patients. Data analysis was carried out using SPSS version 20.0.
UNASSIGNED: The results shows significantly increased skin temperature, prolonged SSR latency (bilaterally) and decreased SSR amplitude (bilaterally) among patients affected with psoriasis compared to control subjects. There is a positive correlation between SSR latency with PDI and a negative correlation between SSR amplitude and PDI in psoriasis patients.
UNASSIGNED: SSR reveals sympathetic sudomotor dysfunction and increased skin temperature in psoriasis. Furthermore, there is a link between increased SSR latency and PDI, which shows that local nervous system impairment significantly contributes to the inflammatory process in psoriasis. Thus, SSR can be used as a complementary tool for the early identification and assessment of epidermal barrier integrity in psoriasis patients, along with the clinician\'s standard protocols.

OBJECTIVE: The use of skin care formulations with acidic pHs is seen as an effective method to maintain the acidic mantel of the skin; however, because the skin pH varies depending on the area of the body and as data are lacking for the skin pH of the feet, there was a need to examine whether this assumption holds true for skin care formulations designed for the foot. Thus, three foot creams formulated with a neutral, acidic or alkaline pH were compared with each other as well as to an untreated control group in order to analyse their impact on skin pH, hydration and general skin condition.
METHODS: An exploratory clinical investigation with 60 enrolled subjects, half of whom had a diagnosis of diabetes (type 1 or type 2), was undertaken. The investigation followed a randomized, double-blind, balanced incomplete block design (BIBD) including intra-individual comparison (before and after treatment). Evaluations of skin pH and hydration were carried out using a pH meter and a Corneometer respectively. Objective evaluation of skin condition for efficacy assessment was performed by a trained grader. For tolerability evaluation, objective and subjective dermatological assessments were performed.
RESULTS: At the end of the treatment period, the skin pH was largely unchanged at five out of six of the test areas, with the mean value for each treatment group using test products showing similar fluctuations as the untreated control group. Furthermore, the skin condition parameters studied all improved by a comparable magnitude for each of the treatment groups using the test products, whereas the untreated control group experienced a worsening of the skin condition parameters.
CONCLUSIONS: The results of this investigation suggest that where the skin of the foot is concerned, the pH of skin care formulations has no (physiologically) relevant influence on the skin\'s pH in either diabetic or non-diabetic subjects. Furthermore, the expectation that acidic formulations would be more beneficial for the skin\'s condition was not found to hold true for the skin of the foot, as no significant difference was observed between the performance of the three test products investigated in this study.
OBJECTIVE: L’utilisation de formulations de soins cutanés à pH acide est considérée comme une méthode efficace pour préserver le manteau acide de la peau. Cependant, comme le pH de la peau varie en fonction de la zone corporelle et comme les données manquent concernant le pH de la peau des pieds, il était nécessaire d’examiner si cette hypothèse est vraie pour les formulations de soins cutanés conçues pour le pied. Ainsi, 3 crèmes pour les pieds à pH neutre, acide ou alcalin ont été comparées entre elles, ainsi qu’à un groupe témoin non traité, afin d’analyser leur impact sur le pH de la peau, l’hydratation et l’état général de la peau. MÉTHODES: Une étude clinique exploratoire a été menée sur 60 sujets inclus, dont la moitié avait reçu un diagnostic de diabète (de type 1 ou de type 2). L’étude a suivi une conception randomisée, en double aveugle, en blocs incomplets équilibrés (balanced incomplete block design, BIBD), comprenant une comparaison intra-individuelle (avant et après le traitement). Les évaluations du pH de la peau et de l’hydratation ont été réalisées à l’aide d’un pH-mètre et d’un cornéomètre, respectivement. Une évaluation objective de l’état de la peau a été réalisée par un évaluateur formé en ce qui concerne l’évaluation de l’efficacité. Pour l’évaluation de la tolérance, des évaluations dermatologiques objectives et subjectives ont été réalisées. RÉSULTATS: À la fin de la période de traitement, le pH de la peau était en grande partie inchangé dans 5 des 6 zones de test, la valeur moyenne pour chaque groupe de traitement utilisant des produits testés montrant des fluctuations similaires à celles du groupe témoin non traité. En outre, les paramètres de l’état de la peau étudiés se sont tous améliorés dans une mesure comparable pour chacun des groupes de traitement utilisant les produits à l’étude, tandis que le groupe témoin non traité a présenté une aggravation des paramètres de l’état de la peau.
CONCLUSIONS: Les résultats de cette étude indiquent qu’en ce qui concerne la peau du pied, le pH des formulations de soins de la peau n’a pas d’influence (physiologiquement) pertinente sur le pH de la peau chez les sujets diabétiques ou non diabétiques. En outre, l’attente selon laquelle des formulations acides seraient plus bénéfiques pour l’état de la peau n’a pas été confirmée pour la peau du pied, car aucune différence significative n’a été observée entre les performances des 3 produits testés étudiés dans cette étude.

BACKGROUND: An important trend in the personal care industry involves the development of advanced personal cleaning products that not only provide skin mildness but support skin\'s acid mantle properties and skin\'s natural antimicrobial defence function.
OBJECTIVE: The objective of this study was to develop a controlled forearm washing ex vivo method for assessing the impact of personal cleansing products on skin\'s acid mantle properties and antimicrobial defence against transient bacteria.
METHODS: We developed a controlled forearm washing ex vivo method (ex vivo NET method) to compare the impact of two representative personal cleansing products on skin\'s acid mantle properties and antimicrobial defence against transient bacteria: one was a low-pH skin cleanser, and the other was high-pH soap cleanser. Skin pH was measured at baseline and 4 h after the product application. Concurrently, D-squame tape stripping procedure was followed to sample the stratum corneum surface layers. Then, two selected transient bacteria, Staphylococcus aureus and Escherichia coli, were inoculated onto the D-squame tapes and incubated under controlled conditions, respectively. The residual bacteria counts can provide an objective measure of skin\'s acid mantle properties against transient bacteria. Results from the ex vivo NET method were compared with the traditional in vivo cup-scrub RET method.
RESULTS: The skin pH was significantly lower 4 h after washing the forearm with the low-pH cleanser versus the high-pH soap, consistent with literatures. Interestingly, the skin surface washed by the low-pH cleanser showed significantly higher hostility against representative transient bacteria as demonstrated by the lower counts of S. aureus by 1.09 log and E. coli by 0.6 log versus the high-pH soap based on the ex vivo NET method. Results from the ex vivo NET method were further supported by the traditional in vivo RET method which also showed the skin washed by the low-pH cleanser had significantly lower counts of S. aureus and E. coli versus the high-pH soap.
CONCLUSIONS: The skin\'s acid mantle properties and antimicrobial defence can be directly impacted by the personal cleansing products. The low-pH skin cleanser works better than the high-pH soap for supporting skin\'s acid mantle properties and antimicrobial defence against transient bacteria. Results from the ex vivo NET method are consistent with the in vivo RET method. It is important that the ex vivo NET method offers many advantages since it is quicker to run with higher throughput and has better safety without the constraint of inoculating harmful microorganisms onto the human subjects.
BACKGROUND: Une tendance importante du secteur des soins personnels est de développer des produits d\'hygiène personnelle sophistiqués qui non seulement rendent la peau plus douce, mais favorisent également les propriétés du manteau acide de la peau et la fonction de défense antimicrobienne naturelle de la peau.
OBJECTIVE: L\'objectif de cette étude était de développer une méthode ex vivo de lavage contrôlé des avant-bras pour évaluer l\'impact des produits d\'hygiène personnelle sur les propriétés du manteau acide de la peau et la défense antimicrobienne contre les bactéries transitoires. MÉTHODES: Nous avons développé une méthode ex vivo de lavage contrôlé des avant-bras (méthode NET ex vivo) pour comparer l\'impact de deux produits d\'hygiène personnelle représentatifs sur les propriétés du manteau acide de la peau et la défense antimicrobienne contre les bactéries transitoires: d\'une part un nettoyant pour la peau à pH faible, d\'autre part un savon nettoyant à pH élevé. Le pH de la peau a été mesuré à l\'entrée dans l\'étude et quatre heures après l\'application du produit. Parallèlement, une procédure de stripping par ruban adhésif D-Squame a été suivie pour prélever des couches de surface de la couche cornée. Ensuite, deux bactéries transitoires sélectionnées, S. aureus et E. coli, ont été inoculées sur les rubans adhésifs D-Squame et incubées dans des conditions contrôlées, respectivement. Le nombre de bactéries résiduelles peut fournir une mesure objective des propriétés du manteau acide de la peau contre les bactéries transitoires. Les résultats de la méthode NET ex vivo ont été comparés à la méthode RET in vivo traditionnelle par coupe-grattage. RÉSULTATS: Le pH de la peau était significativement inférieur quatre heures après le lavage des avant-bras avec le nettoyant à pH faible en comparaison avec le savon à pH élevé, conformément à la littérature. Il est intéressant de noter que la surface de la peau lavée au moyen du nettoyant à pH faible présentait une hostilité significativement plus élevée contre les bactéries transitoires représentatives, comme démontré par le nombre inférieur de S. aureus de 1,09 log et d\'E. coli de 0,6 log, en comparaison avec le savon à pH élevé, sur base de la méthode NET ex vivo. Les résultats de la méthode NET ex vivo ont été encore par la méthode RET in vivo traditionnelle, laquelle a également démontré que la peau lavée à l\'aide du nettoyant à pH faible présentait des nombres significativement plus faibles de S. aureus et d\'E. coli que celle lavée à l\'aide du savon à pH élevé.
CONCLUSIONS: Les propriétés du manteau acide de la peau et la défense antimicrobienne peuvent être directement affectées par les produits d\'hygiène personnelle. Le nettoyant de la peau à pH faible fonctionne mieux que le savon à pH élevé pour ce qui est de favoriser les propriétés du manteau acide de la peau et la défense antimicrobienne contre les bactéries transitoires. Les résultats de la méthode NET ex vivo sont cohérents avec la méthode RET in vivo. Il est important de noter que la méthode NET ex vivo offre de nombreux avantages étant donné qu\'elle est plus rapide à exécuter avec une capacité plus élevée et offre une meilleure sécurité sans la contrainte d\'inoculer des micro-organismes nocifs à des sujets humains.

Triacylglycerols (TG) play an important role in skin homeostasis including the synthesis of ω-O-acylceramides (acylCER) required for skin barrier formation by providing linoleic acid (C18:2n6). However, the overall relationships of TG species with various ceramides (CER) including CER-NP, the most abundant CER, ω-O-acylCER, and another acylCER, 1-O-acylCER in human SC, remain unclear. Therefore, we investigated these relationships and their influence on skin health status in healthy Korean adults. Twelve CER subclasses including two ω-O-acylCER and two 1-O-acylCER were identified with CER-NP consisting of approximately half of the total CER. The ω-O-acylCER species exhibited positive relationships with TG 52:4 and TG 54:2 containing C18:2, while interestingly, 1-O-acylCER containing ester-linked C14:0 and C16:0 demonstrated positive relationships with TG 46-50 including C14:0 and C16:0, respectively. In addition, CER-NP and CER-NH showed positive correlations with TG 52-54 containing C18:2 or C18:3. A lipid pattern with higher levels of CER including CER-NP and ω-O-acylCER with TG 54 and TG with 5-6 double bonds was related to good skin health status, especially with acidic skin pH. Collectively, TG with increased chain length and unsaturation seemed to improve CER content, and profiles such as higher acylCER and CER-NP improved skin health status by fortifying skin barrier structure.

OBJECTIVE: Skin care plays an important role in the prevention of the development of pressure ulcers. The aim of this study was to determine the effect of skincare with a body pH-compatible cleansing cloth on the development time of pressure ulcers and on skin pH.
METHODS: This experimental research was conducted with 156 patients hospitalized in intensive care clinics of a state hospital between September 2019 and 2020. The sample was calculated with a power of 80% and a significance level of 0.05 (α error) and as a result, 78 elderly patients formed the intervention group and another 78 elderly patients made up the control group. Data were collected using the Elderly Information Form, Braden Risk Assessment Scale, Pressure Ulcer Staging Tool and Skin pH Measurement Form. The pre- and post-care skin pH of both groups was measured with a skin pH meter. P < 0.05 was considered statistically significant.
RESULTS: The average development time for pressure ulcers was 14.9 days in the control group, 18.9 days in the intervention group and the difference was not statistically significant (p > 0.05). Skin pH decreased in the intervention group after the skin care routine was applied, whereas it increased in the control group.
CONCLUSIONS: It can be said that care of one\'s skin with a body pH-compatible cleansing cloth has a positive effect on the development time of pressure ulcers and also positively changes the skin pH to acidic.

Dysbiosis of the human skin microbiome has long been associated with changes to the pH of the skin, dermal immune function and chronic skin conditions. Dermatological issues have been noted as the most prevalent medical presentation in the microgravity environment of space. The change in gravitational forces has been implicated in human immuno-suppression, also impacted by changes in the gastrointestinal-skin axis and its impact on Vitamin D metabolism, altered microbial gene expression in resident flora (leading changes in biofilm formation) and increased virulence factors in potential pathogens. There are also other stressors to the skin microbiome unique to space travel, including increased exposure to radiation, prolonged periods of dry washing technique, air quality and changes in microbe replication and growth parameters. Optimal microbiome health leads to enhanced skin barrier manufacture and maintenance, along with improved skin immune function and healing. In a microgravity environment expected to be experienced during long space flights, disruptions to the skin microbiome, coupled with increased virulence of pathological viruses and bacteria has implications for holistic skin health, astronaut cognitive function and mental health, and is coupled with slowed rates of wound healing. Scenario management for holistic skin health and restoration of microbiome homeostasis on long space flights require consideration.