Comparison and correlation between stinging responses to lactic acid and bioengineering parameters

Does sensitive skin lie in epidermal barrier impairment or abnormalities? Results from an observational study assessing biophysical parameters

BACKGROUND

The pathophysiology of sensitive skin is largely unknown and no univocal data on the role of the epidermal barrier impairment have been identified. The aim of this study was to assess whether subjects with or without sensitive skin differ for some biophysical skin parameters, which reflect skin barrier integrity or skin hyperactivity.

METHODS

This observational, cross-sectional study included adult volunteers not affected with chronic inflammatory skin diseases who attended the Unit of Dermatology and the Center of Cosmetology of the University of Ferrara, Ferrara, Italy, between March 2021 and November 2022. All subjects, subdivided into those with or without sensitive skin, based on either Lactic Acid Stinging Test (LAST) result or a questionnaire-based skin sensitivity score ≥4, were tested for transepidermal water loss (TEWL), skin elasticity and hydrations and dermographism.

RESULTS

One hundred and eighty-seven subjects were included. No significant differences in terms of TEWL, elasticity and hydration levels were recorded between subjects with sensitive skin and those without, subdivided according to both the LAST result and the questionnaire score. Dermographism was elicited more in subjects with sensitive skin than in the others, although without statistical significance.

CONCLUSIONS

The study failed to find significant biophysical differences between sensitive and non-sensitive skin. Therefore, the role of skin barrier impairment does not appear to be a necessary condition in determining an abnormal skin sensitivity to potentially unpleasant and irritating stimuli. These findings indirectly support the relevance of a peripheral sensory neural hyperactivity in the pathophysiology of sensitive skin.

MiRNA-224-5p regulates the defective permeability barrier in sensitive skin by targeting claudin-5

BACKGROUND

Sensitive skin is hypersensitive to various external stimuli and a defective epidermal permeability barrier is an important clinical feature of sensitive skin. Claudin-5 (CLDN5) expression levels decrease in sensitive skin. This study aimed to explore the impact of CLDN5 deficiency on the permeability barrier in sensitive skin and the regulatory role of miRNAs in CLDN5 expression.

MATERIALS AND METHODS

A total of 26 patients were retrospectively enrolled, and the CLDN5 expression and permeability barrier dysfunction in vitro were assessed. Then miRNA-224-5p expression was also assessed in sensitive skin.

RESULTS

Immunofluorescence and electron microscopy revealed reduced CLDN5 expression, increased miR-224-5p expression, and disrupted intercellular junctions in sensitive skin. CLDN5 knockdown was associated with lower transepithelial electrical resistance (TEER) and Lucifer yellow penetration in keratinocytes and organotypic skin models. The RNA-seq and qRT-PCR results indicated elevated miR-224-5p expression in sensitive skin; MiR-224-5p directly interacted with the 3`UTR of CLDN5, resulting in CLDN5 deficiency in the luciferase reporter assay. Finally, miR-224-5p reduced TEER in keratinocyte cultures.

CONCLUSION

These results suggest that the miR-224-5p-induced reduction in CLDN5 expression leads to impaired permeability barrier function, and that miR-224-5p could be a potential therapeutic target for sensitive skin.

From consistent subjective assessment of skin sensitivity severity to its accurate objective scoring

BACKGROUND

Sensitive skin (SenS) is a syndrome leading to unpleasant sensations with little visible signs. Grading its severity generally relies on questionnaires or subjective ratings.

MATERIALS AND METHODS

The SenS status of 183 subjects was determined by trained assessors. Answers from a four-item questionnaire were converted into numerical scores, leading to a 0-15 SenS index that was asked twice or thrice. Parameters from hyperspectral images were used as input for a multi-layer perceptron (MLP) neural network to predict the four-item questionnaire score of subjects. The resulting model was used to evaluate the soothing effect of a cosmetic cream applied to one hemiface, comparing it to that of a placebo applied to the other hemiface.

RESULTS

The four-item questionnaire score accurately predicts SenS assessors' classification (92.7%) while providing insight into SenS severity. Most subjects providing repeatable replies are non-SenS, but accepting some variability in answers enables identifying subjects with consistent replies encompassing a majority of SenS subjects. The MLP neural network model predicts the SenS score of subjects with consistent replies from full-face hyperspectral images (R2 Validation set  = 0.969). A similar quality is obtained with hemiface images. Comparing the effect of applying a soothing cosmetic to that of a placebo revealed that subjects with the highest instrumental index (> 5) show significant SenS improvement.

CONCLUSION

A four-item questionnaire enables calculating a SenS index grading its severity. Objective evaluation using hyperspectral images with an MLP neural network accurately predicts SenS severity and its favourable evolution upon the application of a soothing cream.

Lactic acid sting test and capsaicin test differentially induce facial erythematous reaction in subjects with sensitive skin

BACKGROUND

Sensitivity skin (SS) is a common skin disorders, which have a various of clinical manifestation. Facial erythema is common objective symptom of SS. However, the reasons for the occurrence of erythema in sensitive skin are not fully understood.

AIMS

In this study, we preliminarily explain the possible factors inducing erythema of sensitive skin by evaluating facial erythematous reaction to lactic acid sting test (LAST) and capsaicin test (CAT) in subjects with sensitive skin.

METHODS

A total of 197 subjects were divided into five groups, that is, normal controls (NC), LAST-positive (LAST+ ), both LAST and CAT positive (L+ C+ ), both LAST and CAT negative (L- C- ) and CAT-positive (CAT+ ). Erythema index (EI), a* value, and tissue viability imaging (TIVI) were measured before and after LAST and CAT, The ΔEI, Δa*, and ΔTIVI before and after LAST and CAT were calculated, and the correlation between the scores of CAT, EI values, a* values, and TIVI values were analyzed to clarify the causes of facial erythema.

RESULTS

Our results showed that EI values and a* values were significantly higher in the L+ C+ and CAT+ group than in NC group, TIVI values were higher in the L+ C+ group than in NC group. ΔEI and Δa* values after LAST did not differ significantly among five groups. However, ΔEI values in L+ C+ group were higher than that in L- C- group, while Δa* values were higher in CAT+ group than in NC. Moreover, ΔTIVI values in L+ C+ group and CAT+ group were also significantly higher than that in NC group after capsaicin stimulation. CAT scores correlated positively with EI, a* and TIVI values.

CONCLUSION

Our results suggest that sensitive skin subjects with positive CAT are more likely to experience erythema reactions, and vasodilation is more pronounced after capsaicin stimulation. Reducing vascular and neural hyperreactivity could be therapeutic target in management of facial erythema in subjects with sensitive skin.

Rosacea and seborrheic dermatitis differentially respond to lactic acid sting and capsaicin tests in Chinese women

BACKGROUND

Although rosacea and seborrheic dermatitis share some symptoms of sensitive skin, whether they respond differently to lactic acid sting and capsaicin tests, common tests for diagnosis of sensitive skin, is unknown.

OBJECTIVES

To reveal the cutaneous responses to lactic acid sting (LAST) and capsaicin test (CAT) in females with either rosacea vs. seborrheic dermatitis.

METHODS

A total of 60 patients with rosacea, 20 patients with seborrheic dermatitis and 40 normal controls were enrolled in the study. Their skin sensitivity to stimuli were evaluated following topical application of either 10% lactic acid solution or 0.001% capsaicin solution. Transepidermal water loss (TEWL) rates and erythema indexes were also measured on the face.

RESULTS

In comparison to normal controls, the positive rate to either LAST or CAT was significantly higher in subjects with rosacea (p < 0.001), but not in that with seborrheic dermatitis. Similarly, individuals with rosacea displayed a higher positive rate to both LAST and CAT than those with seborrheic dermatitis and normal controls (p < 0.001). In parallel, the LAST scores and CAT scores in individuals with rosacea were significantly higher than in that with either seborrheic dermatitis or normal controls (p < 0.001). The baseline TEWL rates and erythema indexes were higher in individual with rosacea than in normal controls (p < 0.001). But the baseline TEWL rates and erythema indexes did not differ significantly between subjects with rosacea and that with seborrheic dermatitis. Moreover, LAST scores and CAT scores correlated positively with TEWL (p < 0.0001). TEWL rates were higher in CAT positive than in CAT negative subjects (p < 0.0001). Finally, erythema index correlated positively with CAT scores (p < 0.0001), but not with LAST scores (p = 0.0842).

CONCLUSIONS

Skin responses to LAST and CAT differ between individuals with rosacea and those with seborrheic dermatitis, possibly due to the differences in epidermal permeability barrier and the neurovascular hyperreactivity. The higher LAST and CAT scores, as well as positive rates of both LAST and CAT can be attributable to inferior permeability barrier and the neurovascular hyperreactivity in subjects with rosacea.

Explore highly relevant questions in the Baumann skin type questionnaire through the digital skin analyzer: A retrospective single-center study in South Korea

BACKGROUND

Baumann skin type questionnaire (BSTQ) has been widely used for evaluating skin types in dermatology. However, it requires excessive assessment time and lacks sufficient clinical validation for the Asian population.

AIMS

We aimed to establish optimized BSTQ based on dermatological assessment of the Asian population.

METHODS

This was a single-center retrospective study, where the patient completed a modified BSTQ and a digital photography examination. The answers to four question groups for evaluating skin properties, including oily versus dry (O-D), sensitive versus resistant (S-R), pigmented versus non-pigmented (P-N), and wrinkled versus tight (W-T) were compared with the measurements. Highly relevant questions are selected using two different strategies and used to determine the threshold level, which was compared with skin-type measurement.

RESULTS

In O-D, S-R, P-N, and W-T, 3-5 out of 6, 2-6 out of 9, 3-6 out of 7, and 4-9 out of 11 questions were selected, respectively. As a result, skin type scores from two strategies and measurements showed similar Pearson correlation coefficient values compared to modified BSTQ (for O-D and sebum, 0.236/0.266 vs. 0.232; for O-D and porphyrin, 0.230/0.267 vs. 0.230; for S-R and redness, 0.157/0.175 vs. 0.095; for S-R and porphyrin, 0.061 vs. 0.051; for P-N and melanin pigmentation, 0.156/0.208 vs. 0.150; for W-T and wrinkle, 0.265/0.269 vs. 0.217).

CONCLUSION

Two strategies for optimizing BSTQ are proposed and validated for Asian patients. Compared to the BSTQ, our methods show comparable performance with a significantly reduced number of questions.

Clinical studies in Chinese subjects investigating the tolerance and soothing efficacy of a cream and balm containing 4-t-butylcyclohexanol on the sensitivity of facial skin

INTRODUCTION

Asian subjects are particularly prone to skin sensitivity. We developed a facial cream and balm containing 4-t-butylcyclohexanol to provide skin comfort and a soothing effect for sensitive skin.

OBJECTIVES

Assess the dermatological and ophthalmological tolerance and efficacy in improving skin sensitivity of face cream and balm under normal conditions of use by a population known to be particularly prone to this problem.

METHODS

In a monocentric non-randomized open trial, the cream or balm was applied twice daily to the face, neck, and eye contour of 33 stinger subjects with hypersensitive skin (22-63 years old). Assessments included dermatological and ophthalmological physical and functional signs on Day 1 (D1), D8, and D22, and cosmetic acceptability, cutaneous sensitivity according to a stinging test and the sensitive scale, and the soothing efficacy according to a questionnaire on D22.

RESULTS

The cream and balm were very well tolerated. Immediately after application, subjects reported a reduction in the skin's hypersensitivity (93.9% of subjects for the cream and 81.8% for the balm), skin redness (90.9% of subjects for the cream and 87.9% for the balm), sensations of tightness (93.9% for the cream and 97.0% for the balm), and discomfort sensations (93.9% for the cream and 87.9% for the balm). After 21 days, the application of the cream and balm decreased the stinging scores by 65% and 41%, respectively, with 94% and 77% of subjects showing an improvement, respectively. The sensitivity scale questionnaire indicated that the cream and balm significantly and profoundly decreased all negative signs, for example, irritability, stinging, general discomfort, redness, and dryness on D22 compared to D1. On D22, all 15 parameters recorded were improved by 89%-100% by the cream and by 74%-100% by the balm. The majority (90.9% and 96.8% of subjects using the cream and balm, respectively) of the subjects noticed positive changes in their skin condition after using the product for 21 days.

CONCLUSIONS

The cream and balm were very well-tolerated. This study demonstrated that both products controlled and markedly reduced skin hypersensitivity in Asian subjects, with an immediate and lasting skin soothing and repairing effect over 21 days.

The Challenges in Investigating the Pathogenesis of Sensitive Skin by Noninvasive Measurements: A Systematic Review

Sensitive skin (SS) is a common cutaneous condition that seriously affects people's quality of life, but studies of sensitive skin pathogenesis are unclear, the exploration are ongoing, and the biophysical properties of sensitive skin disagree with the study results. In this paper, we summarize the noninvasive biophysical and imaging instrumental methods used for sensitive skin and provide support for the classification of sensitive skin subtypes to prescribe precise treatment. PubMed and Web of Science databases were searched according to PRISMA guidelines for articles from January 1971 to May 2022 that used noninvasive biophysical or imaging methods to monitor adult subjects with sensitive skin. The quality of the included articles was determined based on 22 items of the STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) statement. A total of 55 studies were included, representing 8 biophysical and 5 imaging methods and their applications in treatment efficacy evaluation studies. The biophysical parameter and cutaneous morphological property changes in sensitive skin subjects were observed. The quality of the studies was relatively low, and there was high variability in results between studies. Several parameters have shown tremendous potential in exploring the pathogenesis with different sensitive skin subtypes: type I may be detected with higher transepidermal water loss and lower stratum corneum hydration values, as well as with thinner epidermis with a shallower and more irregular honeycomb structure; Type II and III are more prone to higher blood flow, lower current perception threshold than normal skin. This systematic review identifies key reasons for the lack of uniform trends in noninvasive measurements and recommends the use of effective selection instruments or relevant parameters to explore the pathogenesis of sensitive skin, and to differentiate the subtypes of sensitive skin for achieving the precise treatment.

Stratum corneum hydration in healthy adult humans according to the skin area, age and sex: a systematic review and meta-analysis

Stratum corneum (SC) hydration is one of the most important skin biophysical parameters, which is affected by age, sex and anatomic site. We conducted a systematic review and meta-analysis to provide detailed information on baseline values of SC hydration in healthy human adults, according to the skin area, age and sex. The databases Medline, Embase, Web of Science and Scopus were searched for primary reports, with in vivo corneometry measurements, which were conducted on disease-free skin of human subjects, aged 18+ years in English. Risk of bias was evaluated using the critical appraisal tools for JBI Systematic Reviews, and only low-risk studies were selected. The comparison was performed in each skin area between males and females and also between young- and middle-age subjects. Among 323 Retrieved titles, full texts of 259 articles were read, and 240 studies were excluded due to unclear or insufficient reporting of SC hydration, as well as high or medium risk of bias. 19 studies (including 113 records) providing data about SC hydration in 12 skin areas were included in the final data synthesis. Pooled sample sizes ranged from n = 32 for lips to a maximum of n = 3202 for cheeks. The lowest hydration of 12.5 [95% CI 11.05-13.94] was reported for the back, and the highest hydration of 64.34) [95 CI% 62.07-64.59] for the periorbital area. Facial skin showed higher water content compared with other areas. There were also site-dependent differences in the hydration level of the facial skin. Comparisons between two age groups, and male and female participants, did not show any statistically significant differences. The main limitation was we included studies using only one measurement device. The quality of reporting SC hydration in humans should be increased in future studies.

Biophysical properties of redness-prone skin in Korean women

BACKGROUND

Facial skin redness can have a negative impact on the quality of life. In this study, we investigated the skin biophysical parameters associated with facial skin redness as a function of aging.

METHODS

Our aims were as follows: (1) to understand the impact of non-pathological facial skin redness on the quality of life of Korean women through a survey; and (2) compare skin biophysical properties between women with and without facial skin redness.

RESULTS

Women aged between 20 and 39 years perceived their own facial skin redness at a higher rate than those aged ≥40 years. In addition, in redness-prone women, the intensity of skin redness and skin surface perfusion were higher, while skin hydration was lower regardless of age. In redness-prone women aged ≥40 years, the values for transepidermal water loss, elasticity, and skin thickness were lower, and the mean pore depth was greater. Facial redness intensity was higher, and the distribution was wider in redness-prone younger women, while only redness intensity increased in the older age group.

CONCLUSIONS

Overall, redness-prone women aged ≥40 years had weaker skin properties. Our study indicated the age-related biophysical characteristics of non-pathological facial skin redness. We believe that our findings will help improve its negative effects.

An objective skin-type classification based on non-invasive biophysical parameters

BACKGROUND

Despite the invention of various non-invasive bioengineering tools, skin-type analysis has largely been based on subjective assessments. However, advancements in the functional cosmetic industry and artificial intelligence-assisted dermatology are creating a greater demand for an objective skin-type classification system.

OBJECTIVES

To propose an objective skin-type classification system solely based on non-invasive, bioengineering devices; provide reference values applicable to the Korean population; and compare our reference values with those of published studies.

METHODS

Biophysical parameter measurements were obtained from the 2018 International Skin Characteristics Data Bank Project conducted by the Foundation of Korea Cosmetic Industry Institute. The participants were 434 healthy South Korean adults. Each participant was assessed using eight bioengineering devices (Tewameter^® , pH-meter^® , Corneometer^® , Sebumeter^® , Cutometer^® , Spectrophotometer^® , PRIMOS^® lite, and Janus^® ). The measurements were divided into tertiles to determine reference points.

RESULTS

Our objective skin-type classification consists of five main categories (sensitivity, hydration, oiliness, elasticity, and skin tone) and five corresponding subcategories (erythema, roughness, pores, wrinkles, and pigmentation, respectively). Each skin type was assigned based on the reference point of the biophysical parameter, which was established as the tertile value associated with 'unfavourable' skin characteristics. Individuals were categorized as having sensitive skin when the TEWL scores were over 18.0 g/m² /h or the pH was over 5.45; dehydrated skin when the corneometric value measured below 47.17 A.U.; oily skin when the sebumetric value exceeded 70 μg/cm² ; and loose skin when the cutometric R² value was below 0.68 E/mm.

CONCLUSIONS

This study is the first to provide a comprehensive skin-type classification system based solely on non-invasive biophysical parameters. As measurement data accumulate, the reference points will progress to become more accurate, and they will be subdivided according to gender, age, and ethnic group. Therefore, our classification system serves as a basis for artificial intelligence-based skin-type analysis.

Seasonal changes in the physiological features of healthy and sensitive skin

BACKGROUND

The effects of seasonal factors on sensitive skin (SS) have been reported intensively, but the mechanisms still remain poorly understood.

OBJECTIVE

To investigate the effects of seasonal factors on SS, by comparing the physiological changes in the healthy skin and different subgroups of SS with seasonal variation.

METHODS

Through a questionnaire survey, lactic acid sting test, and capsaicin test, qualified subjects were classified into four groups: healthy skin, only lactic acid sting test positive (LAST(+)/CAT(-)), only capsaicin test positive (LAST(-)/CAT(+)), and both positive (LAST(+)/CAT(+)). Skin physiological parameters were measured in winter and summer.

RESULTS

A total of 140 subjects completed the study. Significant differences were found in transepidermal water loss (TEWL), skin pH, and cutaneous blood flow (CBF) between winter and summer in the four groups. There were significant differences in stratum corneum hydration (SCH) of the LAST(+)/CAP(-) and LAST(+)/CAP(+) groups, current perception threshold (CPT) at 250 Hz of the LAST(+)/CAT(+) group, and epidermal density of the healthy skin group between the two seasons. Sum of the scores of sting (SSS) showed a close correlation with TEWL, SCH, pH, CPT at 250 Hz, and epidermal density. Sum of the scores of burning (SSB) showed a strong correlation with TEWL, pH, CPT at 250 Hz and 5 Hz, and epidermal density.

CONCLUSIONS

Seasonal variation influences the skin barrier function of different types of sensitive skin at different levels. We therefore strongly suggest that, with seasonal variation, different treatments will be undertaken for different subgroups of sensitive skin.

Proposal of a self-assessment questionnaire for the diagnosis of sensitive skin

Background

Sensitive skin is very common and distressing. Its diagnosis may be difficult with the tools/methods available at the moment.

Aims

To assess the reliability of a self‐assessment questionnaire for the diagnosis of sensitive skin, using the results of lactic acid stinging test (LAST) as a reference for the identification of subjects suffering from this condition. A further objective was to identify the questionnaire cutoff score that better discriminates between subjects with or without sensitive skin.

Patients/methods

Among the adult volunteers included in this observational, cross‐sectional study, both LAST‐positive subjects, who were considered as having sensitive skin (“patients”), and negative ones (“controls”) completed the questionnaire. It consisted of a part for self‐assessing and quantifying (0–10) sensitive skin and another one that included 10 items, each referring to a specific, potentially triggering stimulus. A cumulative score (questionnaire‐based skin sensitivity score, 0–10) was calculated from the sum of all items considered capable of triggering unpleasant skin sensations in real‐life experience.

Results

One hundred and sixty‐two subjects were enrolled, 102 patients and 60 controls; 98 subjects thought they had sensitive skin. The mean questionnaire‐based skin sensitivity score was significantly higher among patients than controls and correlated with skin sensitivity self‐assessments. A cutoff value of 3 was set for the identification of LAST‐positive subjects, with 79% accuracy.

Conclusions

The study self‐assessment questionnaire seems to be a reliable tool for diagnosing sensitive skin in clinical practice. These results led us to identify a numerical cutoff for detecting propensity to experience sensitive skin.

Questionnaire and Lactic Acid Sting Test Play Different Role on the Assessment of Sensitive Skin: A Cross-sectional Study

BACKGROUND

Questionnaires and lactic acid sting test (LAST) are two widely used methods to identify sensitive skin. However, the self-perceived sensitive skin by questionnaires was not consistent with the determination of LAST.

OBJECTIVE

The aim of the study was to measure the biophysical properties noninvasively of sensitive skin evaluated by questionnaire and LAST and to investigate their correlations with the scores of questionnaire and LAST.

METHODS

A total of 209 healthy Chinese females completed the study. Self-assessment questionnaire and LAST were both performed to identify sensitive skin. Epidermal biophysical properties, including skin hydration, transepidermal water loss (TEWL), sebum content, erythema index (EI), a* value, L* value, skin elasticity, and skin pH, were measured with noninvasive instruments.

RESULTS

The frequency of sensitive skin was 50.2% and 66.0% by questionnaire and LAST, respectively. Subjects with self-assessed sensitive skin had a slightly higher LAST positive rate. Skin hydration, sebum content, a* and EI values were significantly higher in the self-assessed sensitive skin group, while TEWL, a* and EI values increased but L* value decreased with significance in the LAST positive group. The LAST stingers among sensitive skin subjects had higher EI but not in the healthy skin subjects. In addition, questionnaire scores positively correlated with skin hydration, sebum content, a* and EI values, while a positive relationship of LAST scores with TEWL, a* and EI values was observed. The scores of questionnaire and LAST both negatively related to L* value.

CONCLUSION

Self-assessed questionnaire is associated with sensitive skin featured by oily and red face without impaired barrier function, whereas LAST is suitable to identify fragile skin barrier and enhanced blood flow on the face. Combination of both methods to diagnose sensitive skin might be more reliable.

Visualizing the in-vivo application of zinc in sensitive skin using reflectance confocal microscopy

Findings obtained on objective assessments to evaluate sensitive skin do not correlate well with the symptomatology. We utilized reflectance confocal microscopy (RCM) to compare transepidermal application of zinc in sensitive and non-sensitive skin. Thirty-six subjects participated in this study. They were divided into groups based on lactic acid sting test (LAST):'stinger' and 'non-stinger'; transepidermal water loss (TEWL) measurements; and sensitivity self-assessments: 'sensitive' and 'non-sensitive'. RCM images were taken to visualize transepidermal application of topically-applied zinc. The intensity of zinc reflectance at different depths was measured by ImageJ software. Based on LAST scores, the 'stinger' group showed significantly higher reflectance of zinc at 8 µm (stratum corneum) [face (P < 0.001), forearm (P = 0.004)], and at 80-104 µm (dermo-epidermal junction layer) on the face. High-TEWL group showed increased zinc reflectance at 8-24 µm (tight junction layer, P < 0.001). There were no significant differences amongst subjects self-reporting 'sensitive' and 'non-sensitive' skin. RCM demonstrates that in sensitive skin, there is deeper and higher reflectance of zinc at multiple depths. Structural differences are also visualized. We suggest that RCM is a useful tool for evaluating skin barrier integrity.

Cutaneous vessel features of sensitive skin and its underlying functions

Background

Following the sufficient studies of the effects of skin barrier impairment and heightened neural reaction on sensitive skin (SS), many scholars have paid great attention to the roles of superficial microvasculature in SS.

Methods

By questionnaire survey, lactic acid sting test, and capsaicin test, eligible subjects were classified as normal skin, only lactic acid sting test positive (LASTP), only capsaicin test positive (CATP), and both positive (both LASTP and CATP). D‐OCT was used to photograph images for evaluating the cutaneous vessels features each group.

Results

Totally 137 subjects completed the study. Compared with LASTN group, the vascular vessels were closer to epidermis in LASTP group. Mesh and branching vessels were more popular in SS than normal skin. High blood vessel density was more prevalent in SS, while low density frequently presented in normal skin. The vascular depth had a closely negative correlation with face flushing and SSS, and vascular shapes had a good positive correlation with face flushing and SSB.

Conclusions

Our study indicates that there is a significant difference in vascular depth, shape, and density between SS and normal skin which is valuable to explore SS pathologic mechanism and to further investigate cutaneous microvasculature functions in SS.

Skin sensitivity evaluation: What could impact the assessment results?

BACKGROUND

For the evaluation results of skin sensitivity, such as clinical parameters, stinging test records and biophysical assessments dates might be impacted by many factors, the influence factors need to be further explored, and the skin sensitivity evaluation process and methodology needed distinction and normalization. In this study, we investigated the changes of sensitive skin indexes and lactic acid stinging test results in different seasons, facial regions, skin photo-type, and living habits.

METHODS

Twenty-four healthy subjects had completed this study. Lactic acid stinging test was performed in different seasons. Transepidermal water loss (TEWL), skin hydration, sebum secretion, and pH were measured in an environment-controlled room. Correlations between stinging responses, skin biophysical parameters, and sensitive skin inducements in different seasons were statistically analyzed.

RESULTS

Skin TEWL, hydration, sebum secretion, and pH values on different facial parts were various. Two-way correlation analysis between the results of lactic acid stinging test in different seasons and the sensitivity factors showed differences between summer, autumn, and winter. The mean scores of lactic acid stinging test increased in autumn. Linear regression analysis of skin sensitivity factors in type III and type IV photobiology skin found that the frequency of sleeping time and eating spicy food in the past of week could infect the sensitive skin evaluation dates statistically (P < .05).

DISCUSSION/CONCLUSIONS

Skin sensitivity assessment results were impacted by seasonal transformation, living habits and customs, and facial regions. These indicted that we should consider above interfering factors when evaluated the skin sensitivity for getting more precise dates.

Association between lactic acid sting test scores, self-assessed sensitive skin scores and biophysical properties in Chinese females

Background

Lactic acid sting test (LAST) is a classical method to identify sensitive skin. However, some subjects with self‐perceived sensitive skin are negative for LAST.

Objective

To determine whether LAST scores are associated with specific phenotype of sensitive skin.

Methods

A total of 292 subjects with self‐perceived sensitive skin were enrolled in this study. The Sensitive Scale was used to evaluate the severity of burning, stinging, itching, tautness, erythema and scaling based on 0–10 scale scores. In addition to the assessment of LAST scores, epidermal biophysical properties were measured using an MPA system.

Results

The Sensitive Scale scores of stinging, itching, tautness and scaling were significantly different between the LAST‐positive and ‐negative groups. However, burning and erythema scores did not differ between the LAST‐positive and ‐negative groups. LAST scores were positively correlated with the Sensitive Scale scores for stinging, itching, tautness and scaling, but not for burning and erythema scores. Moreover, LAST scores negatively correlated with stratum corneum hydration, but positively with transepidermal water loss (TEWL) rates.

Conclusions

Lactic acid sting test scores positively correlated with TEWL rates. LAST scores could be used to identify subjects with sensitive skin characterized mainly by stinging and itching, but not those mainly by burning and erythema.

Sensitive Skin: Lessons From Transcriptomic Studies

In 2016, a special interest group from the International Forum for the Study of Itch defined sensitive skin (SS) as a syndrome that manifests with the occurrence of unpleasant sensations (stinging, burning, pain, pruritus, and tingling sensations) after stimuli that should not cause a reaction, such as water, cold, heat, or other physical and/or chemical factors. The pathophysiology of sensitive skin is still poorly understood, but the symptoms described suggest inflammation and peripheral innervation. Only two publications have focused on sensitive skin transcriptomics. In the first study, the authors performed a microarray comparison of SS and non-sensitive skin (NSS) samples and showed differences in the expression of numerous genes in SS and NSS samples. Moreover, in the SS samples, two clusters of genes were identified, including upregulated and downregulated genes, compared to NSS samples. These results provide some interesting clues for the understanding of the pathophysiology of SS. The second study compared SS and NSS samples using RNA-seq assays. This method allowed the identification of long non-coding RNAs (lncRNAs) and differentially expressed mRNAs and provided a comprehensive profile in subjects with SS. The results showed that a wide range of genes may be involved in the pathogenesis of SS and suggested pathways that could be associated with them. In this paper, we discuss these two studies in detail and show how transcriptomic studies can help understand the pathophysiology of sensitive skin. We call for new transcriptomic studies on larger populations to be conducted before putative pathogenic mechanisms can be detected and analyzed to achieve a better understanding of this complex condition.

Skin Biophysical Parameters and Patch Test Results in People Predisposing to Xiaotong Tiegao Induced Irritant Contact Dermatitis

Background

Xiaotong Tiegao (XTT) is an ancient topical Tibetan medicine plaster which is widely used in China. Irritant contact dermatitis (ICD) caused by XTT is very common. It is still unclear why some people are more prone to develop ICD. The aim of this study is to study the baseline skin biophysical parameters and patch test results in individuals predisposing to XTT induced ICD.

Methods

During a four-month period, 149 healthy volunteers with ICD and 50 volunteers without ICD after applying XTT were recruited. The skin biophysical parameters were measured, and contact allergy to 20 common allergens was patch tested, at two weeks after the ICD was recovered.

Results

There were no significant differences in age and sex between ICD and control groups. It was found that skin median melanin value (176.50 vs 189.50, P < 0.05, Mann-Whitney U-test) and erythema value (319.90 ± 70.49 vs 347.93 ± 84.55, P < 0.05, Independent-Samples T test) were much lower in ICD than control group. Overall patch test results were not different, but the positivity rate of nickel sulfate (15.44% vs 4.00%, P < 0.05, Fisher's exact test) was significantly higher in ICD group.

Conclusions

In conclusion, people with nickel allergy, lower values of skin melanin, and erythema are predisposing to develop ICD.

Development of a Novel Approach to Studying Corneodesmosomes and Stratum Corneum Adhesion: Extending Knowledge on the Pathophysiology of Sensitive Skin

BACKGROUND/AIMS

Aberrant skin barrier and intercorneocyte adhesion are potential contributors to the pathomechanism of sensitive skin (SS). Here we aimed to develop a novel and easy-to-apply method to analyze corneodesmosomes and to interrogate potential differences between corneocytes of subjects with SS and non-SS (NSS).

METHODS

Corneocytes of the volar forearm and upper outer quadrant of the left buttock of SS (n = 10) and NSS (n = 8) subjects were extracted as a function of depth using adhesive tape and stained with anti-desmoglein 1 (DSG1) antibody. The total area of corneocytes and the number and average size of cells per tape was estimated using image processing.

RESULTS

The total area of extracted corneocytes and the quantity of DSG1 decreased with depth. The level of decrease, total area of corneocytes, and average area of individual cells differed between anatomical locations. In SS, a larger total area of extracted corneocytes and a larger average cell size per tape was found at all inspected depths.

CONCLUSION

The developed novel and easy-to-apply approach allows investigation of corneodesmosome components. We confirm a role of altered corneocytes in the pathomechanism of SS. The disclosed protocol can further be optimized in studies of skin conditions with strongly affected corneodesmosomes.

Skin care products can aggravate epidermal function: studies in a murine model suggest a pathogenic role in sensitive skin

BACKGROUND

Sensitive skin is defined as a spectrum of unpleasant sensations in response to a variety of stimuli. However, only some skin care products provoke cutaneous symptoms in individuals with sensitive skin. Hence, it would be useful to identify products that could provoke cutaneous symptoms in individuals with sensitive skin.

OBJECTIVE

To assess whether vehicles, as well as certain branded skin care products, can alter epidermal function following topical applications to normal mouse skin.

METHODS

Following topical applications of individual vehicle or skin care product to C57BL/6J mice twice daily for 4 days, transepidermal water loss (TEWL) rates, stratum corneum (SC) hydration and skin surface pH were measured on treated versus untreated mouse skin with an MPA5 device and pH 900 pH meter.

RESULTS

Our results show that all tested products induced abnormalities in epidermal functions of varying severity, including elevations in TEWL and skin surface pH, and reduced SC hydration.

CONCLUSIONS

Our results suggest that mice can serve as a predictive model that could be used to evaluate the potential safety of skin care products in humans with sensitive skin.

Sensitive skin is highly frequent in extrinsic atopic dermatitis and correlates with disease severity markers but not necessarily with skin barrier impairment

BACKGROUND

Sensitive skin is a condition of cutaneous hypersensitivity to environmental factors. Lactic acid stinging test (LAST) is commonly used to assess sensitive skin and composed of four distinct sensations (pain, burning sensation, itch, and crawly feeling). A link between sensitive skin and barrier dysfunction has been proposed in atopic dermatitis (AD) patients. However, clinical and laboratory factors that are associated with sensitive skin remain unelucidated.

OBJECTIVE

To investigate relationship between sensitive skin and AD-associated markers.

METHODS

Forty-two Japanese AD patients and 10 healthy subjects (HS) were enrolled. AD patients were divided into extrinsic (EAD; high IgE levels) and intrinsic (IAD; normal IgE levels) types. We conducted 1% LAST by assessing the four distinct sensations and calculated the frequencies of sensitive skin in EAD, IAD, and HS. We also performed clinical AD-related tests, including transepidermal water loss (TEWL), visual analogue scale (VAS) of pruritus, and quality of life, and measured laboratory markers, including blood levels of IgE, CCL17/TARC, lactate dehydrogenase (LDH) and eosinophil counts, and concentration levels of serum Th1/Th2 cytokines. Filaggrin (FLG) mutations were examined in 21 patients. These values were subjected to correlation analyses with each of the four sensation elements.

RESULTS

According to the standard criteria for LAST positivity, the frequencies of LAST-positive subjects were 54.8% and 10.0% in AD and HS, respectively (P=0.014). EAD patients showed a significantly (P=0.026) higher frequency of positive LAST (65.6%) than did IAD patients (20.0%). Among the four LAST sensation elements, the crawly feeling and pain scores positively correlated with VAS of pruritus, total serum IgE, mite-specific IgE, CCL17/TARC, and/or LDH. There was no association of the LAST scores with serum Th1/Th2 cytokine levels. Notably, neither TEWL nor FLG mutations correlated with LAST positivity or any sensation scores.

CONCLUSIONS

The frequency of sensitive skin is higher in EAD than in IAD. Sensitive skin is associated with AD severity, but not necessarily with barrier condition.

Sensitive Skin: Assessment of the Skin Barrier Using Confocal Raman Microspectroscopy

BACKGROUND/AIMS

Sensitive skin (SS), a frequently reported condition in the Western world, has been suggested to be underlined by an impaired skin barrier. The aim of this study was to investigate the skin barrier molecular composition in SS subjects using confocal Raman microspectroscopy (CRS), and to compare it with that of non-SS (NSS) individuals as well as atopic dermatitis (AD) and allergic rhinoconjunctivitis (AR) subjects, who frequently report SS.

METHODS

Subjects with SS (n = 29), NSS (n = 30), AD (n = 11), and AR (n = 27) were included. Stratum corneum (SC) thickness, water, ceramides/fatty acids, and natural moisturizing factor (NMF) were measured by CRS along with transepidermal water loss and capacitance on the ventral forearm, thenar, and cheek. Sebum levels were additionally measured on the forearm and cheek.

RESULTS

No differences between SS and NSS subjects were found regarding SC thickness, water, and NMF content, yet a trend towards lower ceramides/fatty acids was observed in the cheek. Compared to AD subjects, the SS group showed higher ceramides/fatty acid content in the forearm, whereas no differences emerged with AR. The correlation of macroscopic biophysical techniques and CRS was weak, yet CRS confirmed the well-known lower content of NMF and water, and thinner SC in subjects with filaggrin mutations.

CONCLUSION

The skin barrier in SS is not impaired in terms of SC thickness, water, NMF, and ceramides/fatty acid content. The failure of biophysical techniques to follow alterations in the molecular composition of the skin barrier revealed by CRS emphasizes a strong need in sensitive and specific tools for in vivo skin barrier analysis.

The evaluation of neural and vascular hyper-reactivity for sensitive skin

BACKGROUND

The impaired barrier function has been studied comprehensively but few about the heighted neural and vascular reaction for the pathogenesis of sensitive skin.

METHODS

Lactic acid stinging test (LAST) was used to identify sensitive subjects in selection phase. In the subsequent test phase, the baseline value of the blood flow (BF) and the current perception threshold (CPT) was measured by non-invasive instruments firstly. Then, the 0.001% capsaicin was applied to the nasolabial fold for 5 min. After the capsaicin test (CAT), the BF (immediately after the CAT) and CPT (1 h later after the CAT) were measured again. Blood sample were collected for genetic analysis of four TRPV1 gene single nucleotide polymorphisms between the positive-group and the negative-group.

RESULT

The positive-group had lower baseline value of CPT at 5 and 250 Hz compared with the negative-group, but no difference in baseline value of BF. After the CAT, significant variation in CPT at 5 and 250 Hz values and the BF were found in positive-group but not in negative-group. The genotype frequencies of AG/GG in RS224534 and AC/CC in RS4790523 in positive-group were higher than that of negative-group.

CONCLUSION

The sensitive subjects were prone to be stimulated by capsaicin to trigger neural and vascular hyper-reactivity. The genetic variation of TRPV1 and the unpleasant sensation demonstrate that TRPV1 play an important role in the pathogenesis of sensitive skin. Our study supports that sensory irritation inhibitors and anti-inflammatory compounds should be considered to be added in cosmetics to reduce the heighted neural and vascular reaction of sensitive skin.

Skin sensitivity and intolerance in Shanghai: cumulative influence of different meteorological parameters

BACKGROUND

Although Sensitive skin (SS) conditions are reported to be affected by climate changes, the correlations with meteorological parameters remain mostly unclear.

OBJECTIVE

To investigate the changes of facial skin conditions in different seasons in Shanghai, including the speed and severity of the influences imposed by different meteorological parameters.

METHODS

Totally eighty-one healthy female volunteers completed the study in both spring (May) and summer (August). Evaluations of facial skin conditions included stimulating sensory test, clinical grading and biophysical measurements. Correlations between the meteorological parameters and ΔTEWL as well as clinical parameters were analyzed.

RESULTS

There was no significant difference between two seasons in lactic acid sting test. The stimulation sensations felt by Vitamin B3 (VB3) containing cream was significantly higher in May than that in August. In accordance, baseline visual scores for erythema and scaliness in May were also significantly higher than those scores in August. The baseline transepidermal water loss (TEWL) value was significantly higher in May than that in August. Positive correlations were detected between ΔTEWL and atmospheric pressure on the test day, adjust 3-day and 7-day mean of daily solar radiation respectively. There were negative correlations between ΔTEWL and temperature outside on the test day, adjust 3-day mean as well as adjust 7-day mean of relative humidity.

CONCLUSIONS

Facial skin conditions in summer are better than that in spring in Shanghai. The influences from atmospheric pressure and temperature are relatively quick in speed, while the influences from relative humidity and solar radiation are slow but cumulative.

Rosacea and rhinophyma in the elderly

Rosacea is a chronic inflammatory disease with a predominance of facial manifestations. The prevalence is increasing with age, peaking in the group aged older than 65 years. In 1997, one in eight Americans was aged 65 years and older. By 2030, more than 70 million individuals will be in this age group. This contribution reviews the current understanding of pathogenesis, aggravating factors, classification, comorbidities, and treatment options. Rosacea is a manageable disease that negatively affects quality of life. Rosacea increases the risk of depression and shows a significant proportion of extracutaneous manifestations, in particular ocular rosacea.

Development of a novel method for quantitative evaluation of sensory skin irritation inhibitors

BACKGROUND/AIMS

Sensory skin irritation is regarded as one of the most serious side effects of cosmetic use. Thus, it is desirable to develop good inhibitors of sensory skin irritation. However, it is difficult to quantify the effect of sensory skin irritation inhibitors.

METHODS

We investigated the possibility of using an electrical current perception threshold (CPT) measurement for the quantitative evaluation of these inhibitors. We divided study populations into stinger and non-stinger groups based on their response to 5% lactic acid and assessed CPT values at 2000, 250, and 5 Hz on the cheek. Stingers showed significantly lower CPT values than non-stingers did at 250 and 5 Hz. We also measured CPT values before and after the application of nine materials with inhibitory effects on sensory skin irritation. To investigate the relationship between the change in CPT values and the effect of each material in the clinical stinging test, we conducted the stinging test with the test materials in a 5% lactic acid solution and with a 5% lactic acid solution (positive control).

RESULTS

There was a positive correlation between the change in CPT values and the inhibitory effect that each material had on the stinging test.

CONCLUSION

The change in CPT values can be used for the quantitative evaluation of sensory skin irritation inhibitors .