Putative neuronal mechanisms of sensitive skin

Efficacy and safety of a panthenol-enriched mask for individuals with distinct impaired skin barrier subtypes

BACKGROUND

The protection for different skin types with impaired skin barrier in the market is insufficient.

AIM

To evaluate the efficacy and safety of a panthenol-enriched mask (La Roche-Posay Mask Pro) in addressing various skin barrier impairment subgroups, including dry sensitive, oily sensitive, and oily acne skin.

METHODS

A total of 177 participants were enrolled in the study and divided into three subgroups based on their skin type. Participants used the mask following the specified protocol, with measurements taken for skin hydration, transepidermal water loss (TEWL), sebum content, and skin redness-factors that are directly influenced by skin barrier function. Assessments were conducted at baseline and after 1 day (tested 15 min post-application), 7 days, and 14 days of application using Sebumeter, Tewameter, Corneometer, Mexameter, and VISIA.

RESULTS

Results showed significant improvements in skin parameters across all subgroups. In the dry sensitive skin subgroup, the mask increased skin hydration, sebum content, and reduced redness. For the oily sensitive skin subgroup, the mask regulated sebum production and improved skin hydration. In the oily acne skin subgroup, the mask reduced sebum content, redness, TEWL, and post-inflammatory erythema and hyperpigmentation. Tolerance was excellent for all skin types, with no adverse reactions observed.

CONCLUSIONS

This study highlights the efficacy and safety of the panthenol-enriched LRP Mask Pro for individuals with distinct skin barrier impairment subgroups. The mask's versatile formulation and proven efficacy make it a valuable skincare product for addressing various skin concerns and achieving healthier, more balanced skin.

Characteristics of and foundation application among Chinese females with sensitive skin

OBJECTIVE

We conducted a study on women with sensitive skin of various skin tones to analyse their skin characteristics and preferences for foundation shades.

METHODS

Volunteers were categorized based on their individual typological angle, and their preferences were assessed using self-perception and software-based mass aesthetic assessment. The Baumann Questionnaire is a valuable tool for identifying patients with sensitive skin and gaining a comprehensive understanding of their skin sensitivity. The skin characteristics of two groups were compared using a more suitable classification method.

RESULTS

Individuals diagnosed with sensitive skin typically have skin tones classified as Types I, II and III, with Type I being the most common in sensitive skin cases. The sensitive group exhibited higher levels of transepidermal water loss, lighter skin tone, lower yellowness, increased glossiness, higher haemoglobin content, more acne, fewer blackheads, and fewer pores. Among them, Type I skin is characterized by lower elasticity, increased oiliness, higher hydration levels and fewer visible pores. Type II skin is characterized by lower hydration levels, higher oiliness and increased redness. Type III exhibits more pores, decreased oiliness and enhanced elasticity. Foundations No. 2 and No. 3 are fairer than foundations No. 1 and No. 4. In the self-assessment, Type I and Type II subjects preferred No. 3, while Type III subjects preferred No. 1 and No. 4 because they matched their skin tone. The results of the software evaluation showed that popular aesthetics preferred Type I and Type II to use No. 2, and Type III to use No. 2 and No. 3, as they resulted in a fairer complexion.

CONCLUSION

Sensitive skin of different skin tone types confronts different skin problems. The findings also highlight the public's inclination towards lighter foundation shades, despite the common practice of selecting shades that harmonize with one's inherent skin tone.

Ascorbic Acid Treatments as Effective and Safe Anti-Aging Therapies for Sensitive Skin

The most common signs of aging skin include a decrease in firmness and density, uneven skin tone, and a tendency to erythema. There is an ever-increasing interest in aesthetic treatments that maintain the skin's favorable appearance. However, such therapies are difficult in the case of sensitive skin, defined as a set of stimuli-triggered symptoms (stinging, erythema, burning, and itching) that would not appear in healthy skin. Sensitive skin is common and affects, to varying degrees, about half of the European population. This study was aimed at evaluating the effects of ascorbic acid-a known antioxidant-applied with sonophoresis and microneedling on the signs of photoaging in reactive and erythematous skin. A significant improvement in skin elasticity was observed after a series of tests. A significant reduction in erythema was observed after both therapies. The greatest reduction was observed on the cheeks after applying vitamin C combined with microneedling. At the same time, the results showed an excellent tolerance of both treatments, which proved them to be safe and effective.

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.

Systematic Study of Paeonol/Madecassoside Co-Delivery Nanoemulsion Transdermal Delivery System for Enhancing Barrier Repair and Anti-Inflammatory Efficacy

Sensitive skin is defined as skin with low tolerance and high reactivity. Natural products, such as paeoniflorin and madecassoside, have unique skin care functionality. However, because they are hampered by the skin barrier, paeoniflorin and madecassoside have difficulty penetrating the stratum corneum, resulting in weakened skin barrier repair and anti-inflammatory effects. In addition, there is a lack of detailed studies on the efficacy of paeonol and madecassic in human skin, especially in 3D skin models and clinical trials. To overcome the low transdermal delivery issue, we developed nanoemulsions (PM-NEs) loaded with paeonol and madecassoside to improve their delivery efficiency and promote sensitive skin repair and anti-inflammation effects. Furthermore, systematic evaluations of the efficacy in cell line models, 3D skin models, and clinical trials were conducted. The PM-NEs effectively improved the efficacy of paeonol and madecassoside glucoside transdermal penetration and retention and enhanced cellular uptake. Cellular assays and 3D epidermal models showed that the PM-NEs significantly promoted the secretion of filamentous protein, aquaporin 3, Claudin-1, and hyaluronic acid, and considerably inhibited the secretion of interleukin 1α, interleukin 6, tumor necrosis factor-α, and prostaglandin E₂ compared to free components. Notably, clinical trial data showed that the PM-NEs significantly reduced transepidermal water loss, a* values, erythropoietin, the amount of non-inflammatory acne, and the amount of inflammatory acne in the facial skin. Three levels of systematic studies suggest that co-delivery of paeoniflorin and madecassoside via nanoemulsions is a promising strategy to improve topical delivery efficiency and anti-inflammatory repair efficacy in sensitive skin.

Clinical Evaluation of Conditioned Media of Human Umbilical Cord Blood Mesenchymal Stem Cells for Improvement of Symptoms of Sensitive Skin: Prospective, Single Blinded, Split-face Study

BACKGROUND

The exact definition of sensitive skin is not established yet. Since its high prevalence and significant influence on quality of life, it has become an important topic of research. Among various ingredients, conditioned media from umbilical cord blood-derived mesenchymal stem cells (UCB-MSC-CM) can be a promising source for the treatment of sensitive skin.

OBJECTIVE

We evaluated the efficacy and safety of UCB-MSC-CM on patients with sensitive skin.

METHODS

We designed a randomized, single blinded, prospective, split-face comparison study and enrolled thirty patients. All patients underwent nonablative fractional laser over the entire face before UCB-MSC-CM or normal saline was applied. Each facial area was randomly assigned to undergo treatment with either UCB-MSC-CM or normal saline. We performed three sessions at two-week intervals, and final results were assessed on six weeks after the last session. As an outcome measure, we evaluated a five-point global assessment scale, transepidermal water loss (TEWL), erythema index (EI) and Sensitive Scale-10. Twenty seven subjects were included in final analysis.

RESULTS

The treated side exhibited greater improvement compared to the untreated side based on a five-point global assessment scale. TEWL, EI of the treated side were significantly lower than those of the untreated side throughout study period. Sensitive Scale-10 was significantly improved after treatment.

CONCLUSION

The application of UCB-MSC-CM resulted in improved skin barrier function and reduced inflammatory responsiveness, which could provide beneficial effect on sensitive skin.

[Translated article] Sensitive Scalp: Diagnosis and Practical Management

Sensitive scalp is sensitive skin located on the scalp. Sensitivity is considered primary in the absence of an associated scalp disorder and secondary when caused by conditions such as psoriasis, seborrheic dermatitis, and atopic dermatitis. The clinical manifestations of primary sensitive scalp are subjective. Common presenting symptoms are burning, itching, trichodynia, and dysesthesia, often coinciding with hair loss. Clinically, the skin appears normal or red. An objective diagnosis based on laboratory or histologic findings is not possible. Triggers may be endogenous (e.g., stress and emotional or psychopathological disturbances) or exogeneous (e.g., topical products and cosmetics). Treatment must be individualized. Options include pimecrolimus, hydration with hyaluronic acid, and mesotherapy with plasma rich in growth factors.

Sensitive Scalp: Diagnosis and Practical Management

Sensitive scalp is sensitive skin located on the scalp. Sensitivity is considered primary in the absence of an associated scalp disorder and secondary when caused by conditions such as psoriasis, seborrheic dermatitis, and atopic dermatitis. The clinical manifestations of primary sensitive scalp are subjective. Common presenting symptoms are burning, itching, trichodynia, and dysesthesia, often coinciding with hair loss. Clinically, the skin appears normal or red. An objective diagnosis based on laboratory or histologic findings is not possible. Triggers may be endogenous (e.g., stress and emotional or psychopathological disturbances) or exogeneous (e.g., topical products and cosmetics). Treatment must be individualized. Options include pimecrolimus, hydration with hyaluronic acid, and mesotherapy with plasma rich in growth factors.

Mussel adhesive protein treatment delivered by microneedling for sensitive skin: A clinical study

BACKGROUND

Mussel adhesive protein (MAP) is extracted from the mycelial glands of marine mussels. It has anti-inflammatory properties and may relieve skin itching and other symptoms.

AIMS

Based on the anti-inflammatory effect of MAP, this study was designed to treat sensitive skin (SS) using MAP delivered by skin microneedling.

PATIENTS/METHODS

Twenty-three Chinese female patients with SS were enrolled. Treatments were delivered three times at one-month intervals. Symptom improvement and recurrence rates, treatment safety, and patient satisfaction levels were evaluated.

RESULTS

After one course of treatment, 20 patients had a Symptom Score Reducing Index (SSRI) of >20%, with an effectiveness rate of 87%. At the end of treatment, all patients had an SSRI of >20%, and the effectiveness rate was 100%. Dryness, tightness, desquamation, flushing, burning, itching, and tingling improved. After treatment, the Clinical Erythema Assessment and Lesion Severity Index of Facial Telangiectasia scores were significantly decreased. Clinical photographs following treatment revealed improved erythema reaction and decreased capillary density. During treatment, the patients experienced mild pain and erythema and swelling reaction without exudation. Complications, such as pigmentation changes or scarring, were absent. Additionally, there were no cases of recurrence, and patient satisfaction levels were high.

CONCLUSION

MAP combined with microneedling can help treat SS, showing satisfactory safety outcomes and high patient satisfaction.

MRI-Induced Neurosensory Events in Decorative Black Tattoos: Study by Advanced Experimental Methods

Adverse reactions in tattooed skin during magnetic resonance imaging (MRI) are rare but well known. Previous reports describe sudden burning pain in tattooed skin, sometimes accompanied by mild erythema and oedema when entering MRI scanners. The pathophysiology remains unclear, but simple direct thermal heating can be excluded. It has been hypothesized that MRI-triggered torque and traction create neural sensations from magnetic pigment particles. However, this case enlightens yet another possible mechanism. We present a 35-year-old woman experiencing reoccurring stinging sensations in three decorative black tattoos just seconds after the initiation of the MRI. Single-blind tests with handheld power magnets or a dummy could reproduce painful subjective feelings in her tattooed skin. Similar events were provoked during re-evaluation with MRI. Surprisingly, chemical analyses and electron microscopy of skin samples revealed carbon black as the colouring agent - no iron-based solids were detected. Our case demonstrates that MRI tattoo reactions are not limited to magnetic contaminants alone. More distinct subgroups of MRI-induced reactions may occur. We hypothesize that radiofrequency induction of surface currents in black carbon particles adjacent to sensory axons in the dermis may lead to neurosensations.

Occurrence of Allergens in Cosmetics for Sensitive Skin

Sensitive skin is characterized by symptoms such as stinging and tingling in response to stimuli that usually do not cause unpleasant sensations. Epidemiological studies show that individuals with sensitive skin are more prone to developing skin allergies, although the link between both conditions is unknown. Aiming to evaluate the presence of allergens in facial-skin products for sensitive skin, a pool of 88 cosmetic products from international brands marketed in pharmacies and parapharmacies was analyzed. A list of allergens identified in product labels was compiled and grouped according to their function. Fragrances were the most common allergens, followed by skin-conditioning agents, surfactants, and preservatives. Fragrances presenting the highest use percentages were linalool, benzyl alcohol, geraniol, and citronellol. Overall, the majority of cosmetic formulations were absent of fragrance allergens, being present only in 7% of products. Other allergens were found in most products (95%). This finding should be interpreted with caution, since many of these compounds are rare sensitizers and studies demonstrating their risk for individuals with sensitive skin are lacking. With this study, useful information for health professionals is provided to support their advice and to help consumers choosing cosmetic products.

Determination of Chemical Irritation Potential Using a Defined Gene Signature Set on Tissue-Engineered Human Skin Equivalents

There are no physical or visual manifestations that define skin sensitivity or irritation; a subjective diagnosis is made on the basis of the evaluation of clinical presentations, including burning, prickling, erythema, and itching. Adverse skin reaction in response to topically applied products is common and can limit the use of dermatological or cosmetic products. The purpose of this study was to evaluate the use of human skin equivalents based on immortalized skin keratinocytes and evaluate the potential of a 22-gene panel in combination with multivariate analysis to discriminate between chemicals known to act as irritants and those that do not. Test compounds were applied topically to full-thickness human skin equivalent or human ex vivo skin and gene signatures determined for known irritants and nonirritants. Principle component analysis showed the discriminatory potential of the 22-gene panel. Linear discrimination analysis, performed to further refine the gene set for a more high-throughput analysis, identified a putative seven-gene panel (IL-6, PTGS2, ATF3, TRPV3, MAP3K8, HMGB2, and matrix metalloproteinase gene MMP-3) that could distinguish potential irritants from nonirritants. These data offer promise as an in vitro prediction tool, although analysis of a large chemical test set is required to further evaluate the system.

Understanding the Sensitive Skin Subject to Achieve a More Holistic Diagnosis

Sensitive skin Syndrome (SSS) is a complex global clinical phenomenon that is defined by the self-reported presence of different sensory perceptions, including tightness, stinging, burning, tingling, pain and pruritus and often without objective signs. Due to the subjective nature of this clinical condition, the diagnosis is complex and there is often a disconnect between what subjects feel and what medical professionals can observe. This chapter reviews the known underlying physiology, some of the triggering factors associated with SSS, co-morbidities as well as the psychological impact on individuals suffering from this condition. The goal is to bridge the gap between the physicians’ understanding and the subjects’ perceptions of this real-life condition that affects so many.

Association between chronic idiopathic cough and sensitive skin syndromes is a new argument in favor of common neuropathic pathways: results from a survey on 4050 subjects

Sensitive skin syndrome has a neuropathic origin, which is why it is frequently associated with irritable bowel syndrome. We have looked for a possible association with chronic cough, which is commonly maintained by neurogenic mechanisms, whatever the initial cause(s). A survey was carried out on a representative sample of the population over 15 years of age using the quota method. The questionnaire included sociodemographic data and questions about sensitive skin, the presence of chronic cough, smoking and possible causes of chronic cough. Chronic cough was assessed by the Leicester Cough Questionnaire, and 4050 subjects responded (mean age: 45 years). Overall, 12.2% of subjects with a chronic cough were compared to the 87.8% without any cough. Among them, 72.5% had sensitive skin (vs. 47.8%, p < 0.001); additionally, 17.4% of the subjects with sensitive skin had a chronic cough (vs. 6.9% if no sensitive skin). These proportions were higher if very sensitive skin was reported. The risk of having chronic cough was twice as high if sensitive skin was reported [OR = 1.9 (1.5-2.4), p < 0.001]. The risk of having sensitive skin was also twice as high for chronic cough. Thus, chronic cough and sensitive skin are frequently associated. This association represents a new argument in favor of a neuropathic nature of sensitive skin. Sensitive skin and chronic cough are both modes of overreaction to environmental factors, which tend to be autonomized by neurogenic mechanisms. Dermatologists should ask their patients if they have a chronic cough, and pneumologists should ask about the presence of sensitive skin.

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.

Sensitive Skins May Be Neuropathic Disorders: Lessons from Studies on Skin and Other Organs

Sensitive skin can be considered a neuropathic disorder. Sensory disorders and the decrease in intra-epidermal nerve ending density are strong arguments for small-fiber neuropathies. Sensitive skin is frequently associated with irritable bowel syndrome or sensitive eyes, which are also considered neuropathic disorders. Consequently, in vitro co-cultures of skin and neurons are adequate models for sensitive skin.

An herbal cream reduces erythema of sensitive skin

BACKGROUND

Sensitive skin manifests itself as a syndrome defined by the occurrence of unpleasant sensations such as stinging, burning, and pruritus. Though not life-threatening, it can negatively impact the quality of people's lives because of symptoms and clinical signs. Although some skin care products can alleviate symptoms of sensitive skin, a product that can improve multiple abnormalities of sensitive skin are largely unavailable.

AIMS

To assess the efficacy of a newly developed herbal cream in reducing erythema.

METHODS

A randomized double-blind and self-controlled trial was carried out on a total of 35 volunteers. The test cream (A) was applied topically to one side of the face twice-daily, while the control cream (B) was applied to the other side of the face. Parameters were evaluated prior to, 14, and 28 days after topical applications. Primary endpoints included changes in erythema area, erythema index (EI), and a* value. Transepidermal water loss rates (TEWL), stratum corneum (SC) hydration, and lactic acid sting test (LAST) score, as well as the L* value, served as secondary endpoints.

RESULT

Treatments with either cream A or B markedly reduced erythema area, EI, and a* value. Significant reductions in both TEWL and L* value were also observed following topical applications of either cream A or B. Moreover, cream A decreased LAST score. Finally, the satisfaction rate of cream A was higher than that of cream B.

CONCLUSION

The new herbal cream improves cutaneous biophysical properties in subjects with sensitive skin, especially in reducing erythema.

Sensitive Skin Syndrome: An Update

Sensitive skin syndrome is a widely reported complaint but a diagnostic challenge because of its subjective symptoms and lack of clearly visible manifestations. Epidemiological studies have shown the prevalence of sensitive skin to be as high as 60-70% among women and 50-60% among men. Patients with this syndrome usually have unpleasant sensations when exposed to physical, thermal, or chemical stimuli that normally cause no provocation on healthy skin. Recent studies and newly accepted position papers have provided a more in-depth understanding and consensus of its underlying pathophysiology, associations, diagnosis, and treatment. Since no clinical studies have been conducted about specific treatment protocols, patients with this condition should be provided with personalized skin management. Given this updated knowledge, our review offers an approach to sensitive skin syndrome, with differential diagnoses, and interventions targeting its pathophysiology.

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.

The importance of the neuro-immuno-cutaneous system on human skin equivalent design

The skin is a highly complex organ, responsible for sensation, protection against the environment (pollutants, foreign proteins, infection) and thereby linked to the immune and sensory systems in the neuro-immuno-cutaneous (NIC) system. Cutaneous innervation is a key part of the peripheral nervous system; therefore, the skin should be considered a sensory organ and an important part of the central nervous system, an 'active interface' and the first connection of the body to the outside world. Peripheral nerves are a complex class of neurons within these systems, subsets of functions are conducted, including mechanoreception, nociception and thermoception. Epidermal and dermal cells produce signalling factors (such as cytokines or growth factors), neurites influence skin cells (such as via neuropeptides), and peripheral nerves have a role in both early and late stages of the inflammatory response. One way this is achieved, specifically in the cutaneous system, is through neuropeptide release and signalling, especially via substance P (SP), neuropeptide Y (NPY) and nerve growth factor (NGF). Cutaneous, neuronal and immune cells play a central role in many conditions, including psoriasis, atopic dermatitis, vitiligo, UV-induced immunosuppression, herpes and lymphomas. Therefore, it is critical to understand the connections and interplay between the peripheral nervous system and the skin and immune systems, the NIC system. Relevant in vitro tissue models based on human skin equivalents can be used to gain insight and to address impact across research and clinical needs.

Low maternal care enhances the skin barrier resistance of offspring in mice

Deprivation of maternal care via lack of somatosensory input causes offspring to experience adverse consequences, especially in the central nervous system. However, little is known about the developmental effect of maternal care on peripheral tissues such as the skin, which includes cutaneous sensory neurons. In the present study, we examined the involvement of maternal care in the development of the skin. We investigated offspring reared by early-weaned mother mice who spontaneously showed lower frequency of licking/grooming on nursing. Offspring of early-weaned mothers showed higher resistance against skin barrier disruption than did offspring of normally-weaned mothers, and had normal skin barrier function in the intact trunk skin. In the dorsal root ganglion of early-weaned mother offspring, we also found up-regulation of mRNA levels of the Mas-related G-protein coupled receptor B4 (MrgprB4), which is a marker of sensory neurons that detect gentle stroking. We further found that levels of MrgprB4 mRNA were correlated with the enhancement of skin resistance. The present findings suggest that maternal somatosensory inputs have a developmental impact on the cutaneous sensory neurons of the skin in offspring. Interestingly, the present results suggest that lower maternal care has a benefit on the skin resistance. This provides important information for understanding the development of peripheral tissues in offspring reared under severe conditions such as lower maternal care in the wild.

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.

Diagnosis and Treatment of Sensitive Skin Syndrome: An Algorithm for Clinical Practice

Sensitive skin has traditionally been viewed as a cosmetic problem or as a purely psychosomatic alteration with a major subjective component. Different studies of its pathophysiologic etiology, however, have shown it to be a complex entity that several authors now consider to be a neurodermatological syndrome. Because of this complexity, skin sensitivity can be difficult to diagnose and treat, particularly considering that it may present with another disease. Simple tools applicable to clinical practice are thus necessary to identify and manage this disease as an independent entity. In this study, we perform a practical review of the most recent scientific advances in the area of sensitive skin that justify it being considered an individual entity, and provide tools for its identification and treatment. We propose diagnostic and treatment algorithms based on evidence from the literature and our experience and expertise.

Role of Keratinocytes in Sensitive Skin

Sensitive skin is a clinical syndrome defined by the occurrence of unpleasant sensations such as burning, stinging, tingling, pricking, or itching in response to various normally innocuous physical, chemical, and thermal stimuli. These particular symptoms have led the consideration of a potential dysfunction of the intra-epidermal nerve fibers (IENF) that are responsible for pain, temperature, and itch perception. This neuronal hypothesis has just been reinforced by recent studies suggesting that sensitive skin could become assimilated to small fiber neuropathy. Meanwhile, the involvement of keratinocytes, the pre-dominant epidermal cell type, has so far mainly been considered because of their role in the epidermal barrier. However, keratinocytes also express diverse sensory receptors present on sensory neurons, such as receptors of the transient receptor potential (TRP) family, including Transient Receptor Potential Vallinoid 1 (TRPV1), one of the main transducers of painful heat which is also involved in itch transduction, and Transient Receptor Potential Vallinoid 4 (TRPV4) which is depicted as a heat sensor. While TRPV1 and TRPV4 are expressed both by sensory neurons and keratinocytes, it has recently been demonstrated that the specific and selective activation of TRPV1 on keratinocytes is sufficient to induce pain. Similarly, the targeted activation of keratinocyte-expressed TRPV4 elicits itch and the resulting scratching behavior. So, contrary to classical conception, the IENF are not the exclusive transducers of pain and itch. In light of these recent advances, this review proposes to consider the putative role of epidermal keratinocytes in the generation of the unpleasant sensations characteristic of sensitive skin syndrome.

The Prevalence of Sensitive Skin

Sensitive skin has been described as unpleasant sensory responses to stimuli that should not provoke such sensations. Objectively measurable signs of irritation are not always present in individuals with sensitive skin, however, subjective sensory effects such as, itching, burning, stinging, tightness, and dryness, are consistently present. Given the subjective nature of the phenomenon known as sensitive skin, surveys have been a popular approach to evaluating the prevalence of this condition among the general population, and a number of them have been conducted worldwide. Overall, ~60–70% of women and 50–60% of men report having some degree of sensitive skin. However, there are differences between populations in various geographies, and perceptions of sensitive skin at specific anatomic sites. This article is a review of survey data on the prevalence of self-declared sensitive skin in various geographies, among different gender and age groups, and at various anatomic sites. In addition, we review the factors that may contribute to sensitive skin, and the physiological characteristics associated with this condition, including impaired barrier function and heightened neural reactions.

Will Repeated Ablative Er:YAG Laser Treatment Sessions Cause Facial Skin Sensitivity? Results of a 12-Month, Prospective, Randomized Split-Face Study

Whether multiple laser irradiations affect skin sensitivity is still elusive. We aimed to investigate if repeated ablative erbium:yttrium-aluminum-garnet (Er:YAG) laser therapy could cause or increase skin sensitivity in the treatment areas. Nineteen healthy females received three sessions of a randomized, split-face, Er:YAG laser treatment in a scanning ablative mode (MicroLaserPeel™), with a 6-mm spot size, 8-μm ablative depths, and 30% of pulse overlap first. The next round was conducted in the fractional mode (ProFractional™) at depths ranging from 100 to 150 μm, with one pass by at coverage of 11% in the coagulation mode. Objective biophysical parameters, including transepidermal water loss (TEWL), skin glossiness, epidermal and dermal thickness and density, sensory nerve current perception threshold (CPT), and local blood flow, were measured before and after treatment. Quantitative evaluation of the Er:YAG laser treatment's effect on skin sensitivity is presented. Seventeen volunteers completed a follow-up of 12 months. On days 1 and 3, skin TEWL and epidermal thickness increased, while glossiness decreased. On day 7, there was no significant difference in the skin barrier function between the treated and the control side. Similarly, there was no significant difference in CPT values or local microvascular blood flow between sides at any time point before or after treatment, except that the local microvascular blood flow on the treated side was higher on the first day post-treatment. Er:YAG laser treatment does not influence skin sensitivity in healthy subjects in a long-term follow-up.

A new tool to test active ingredient using lactic acid in vitro, a help to understand cellular mechanism involved in stinging test: An example using a bacterial polysaccharide (Fucogel® )

The stinging test is an in vivo protocol that evaluates sensitive skin using lactic acid (LA). A soothing sensation of cosmetics or ingredients can be also appreciated through a decrease in stinging score. To predict the soothing sensation of a product before in vivo testing, we developed a model based on an LA test and substance P (SP) release using a co-culture of human keratinocytes and NGF-differentiated PC12 cells. A bacterial fucose-rich polysaccharide present in Fucogel^® was evaluated as the soothing molecule in the in vivo stinging test and our in vitro model. Excluding toxic concentrations, the release of SP was significant from 0.2% of lactic acid for the PC12 cells and from 0.1% of lactic acid for the keratinocytes. When the pH was adjusted to approximately 7.4, LA did not provoke SP release. At these concentrations of LA, 0.1% of polysaccharide showed a significant decrease in SP release from the two cellular types and in co-cultures without modifying the pH of the medium. In vivo, a stinging test using the polysaccharide showed a 30% decrease in prickling intensity vs the placebo in 19 women between the ages of 21 and 69. Our in vitro model is ethically interesting and is adapted for cosmetic ingredients screening because it does not use animal experimentation and limits human volunteers. Moreover, Fucogel^® reduced prickling sensation as revealed by the in vivo stinging test and inhibits the neurogenic inflammation as showed by our new in vitro stinging test based on SP release.

Assessment of the efficacy of a new complex antisensitive skin cream

BACKGROUND

Sensitive skin is frequently complaint in dermatology consultation with cutaneous manifestations such as stinging, redness, dryness, and burning sensation that affect the quality of life. Its pathogenesis is mainly related to dysfunction of neurosensory, skin barrier, and also immune activity. The treatment is generally based on continuous and topical therapy by nonirritating complex.

OBJECTIVE

To evaluate the antisensitive function of a new complex cream composed by Yunnan Portulaca oleracea extract, Prinsepia utilis oil, beta-glucan, and sodium hyaluronate extracted from mushroom.

METHODS

A randomized double-blind and self-control study was conducted on 20 selected volunteers with sensitive skin. Subjects applied the test cream to 1 side of the face, and the control cream (tolerance-extreme cream) to the other side of the face, twice daily over 28 days. Evaluations were performed at baseline and at 28 days. Expert clinical grading of facial skin including dryness, roughness, desquamation, and erythema was assessed. Subject self-assessment questionnaires, digital photography and noninvasive bioinstrumentation of hydration, transepidermal water loss, lipid index, skin texture, and wettability were also included in the study.

RESULTS

Products were well tolerated. For all parameters studied, no significant difference was observed between test and control creams. Results showed that test cream provided a statistically significant improvement in clinical grading scores for dryness, roughness, and erythema at 28 days compared to baseline. In addition, statistically significant improvement of skin hydration and texture parameters (eg, smoothness and roughness) was demonstrated. Volunteers' questionnaire revealed self-perceived benefits consistent with expert visual grading.

CONCLUSION

This study confirmed the effectiveness and tolerance of the new complex cream in subjects with sensitive skin. The test cream could serve as a daily care moisturizer for face.

Analysis of sensitive skin barrier function: basic indicators and sebum composition

OBJECTIVES

Sensitive skin (SS) is a condition characterised by high reactivity, low tolerance, and susceptibility to allergies of the skin. Owing to changes in the environment and marketing strategies, as well as the increasing public awareness about skin care, attention to skin condition is gradually increasing. The aim of this study is to explore the differences in the skin barrier of SS and normal skin (NS).

METHODS

A questionnaire survey was conducted and basic indicators of the skin barrier were analysed. It was found that sebum secretion in the SS group was lower than that in the NS group, suggesting that the development of SS might be associated with sebum secretion and its specific components. Next, an ultra performance liquid chromatography-quadruple time-of-flight mass spectrometer was used to identify facial sebum components in female volunteers.

RESULTS

The results showed that the sebum of female volunteers with SS had high levels of ceramides, glycerophosphoethanolamines, and diacylglycerols, and low levels of glucosylceramides, glycerophosphoserines, glycerophosphocholines, and triacylglycerols.

CONCLUSION

Analysis of lipid functions suggested that the main reason for SS development in women might be a barrier dysfunction caused by excessive apoptosis and lack of water. Therefore, anti-allergy additives in cosmetic products that could inhibit apoptosis of keratinocytes and methods to maintain the stability of water molecules in the skin should be further studied.

Skin matters! The role of keratinocytes in nociception: a rational argument for the development of topical analgesics

Treatment of neuropathic pain using topical formulations is still in its infancy. Only few topical analgesic formulations have become available for clinical use, and among these, analgesic creams are still rare. This is unfortunate because analgesic creams offer a number of advantages over patches, such as convenience, ease of adapting the frequency of application, and dose, and “rubbing cream where it hurts” involves the patient much more in the therapeutic process compared to patches and other localized treatment modalities. Although the literature supporting the efficacy and safety of analgesic creams (mostly compounded) is growing since the last decade, most pain physicians have not yet noticed and appreciated the therapeutic potential and clinical value of these creams. This is most probably due to a prejudice that topical application should need to act transdermally, more or less as a slow-release formulation, such as in patches delivering opioids. We will discuss this prejudice and show that there are multiple important targets in the skin to be reached by topical analgesic or anti-inflammatory compounds, and that the keratinocyte is one of those targets. By specifically targeting the keratinocyte, analgesia seems possible, effective, and safe, and thus topical analgesic creams may hold promise as a novel treatment modality for neuropathic pain.

Sensitive skin

Sensitive skin is a clinical condition defined by the self-reported facial presence of different sensory perceptions, including tightness, stinging, burning, tingling, pain and pruritus. Sensitive skin may occur in individuals with normal skin, with skin barrier disturbance, or as a part of the symptoms associated with facial dermatoses such as rosacea, atopic dermatitis and psoriasis. Although experimental studies are still pending, the symptoms of sensitive skin suggest the involvement of cutaneous nerve fibres and neuronal, as well as epidermal, thermochannels. Many individuals with sensitive skin report worsening symptoms due to environmental factors. It is thought that this might be attributed to the thermochannel TRPV1, as it typically responds to exogenous, endogenous, physical and chemical stimuli. Barrier disruptions and immune mechanisms may also be involved. This review summarizes current knowledge on the epidemiology, potential mechanisms, clinics and therapy of sensitive skin.

Skin compatibility and efficacy of a cosmetic skin care regimen with licochalcone A and 4-t-butylcyclohexanol in patients with rosacea subtype I

BACKGROUND

Patients with rosacea often show facial sensitivity to cosmetics or skin care products that can influence the severity of symptoms and exacerbate erythema and inflammation. Nevertheless, special skin care is necessary to address cosmetic concerns and reduce the potential side-effects of topical or oral treatment of the disease. Appropriate skin care should comprise gentle cleansing, effective moisturization, soothing actives, UV protection and concealing pigments to help neutralize the appearance of redness.

OBJECTIVE

To determine the compatibility and efficacy of a skin care regimen (consisting of a cleanser, a day care with SPF25 and a night care) containing licochalcone A (Lic A), an anti-irritant from the licorice plant Glycyrrhiza inflata, and 4-t-butylcyclohexanol (SymSitive(®) ), a substance which acts as a sensitivity regulator, in female subjects with clinically determined subtype I rosacea.

METHODS

Thirty-two test subjects with mild to moderate rosacea used the skin care regimen daily for 8 weeks. Clinical assessment of erythema, subjective irritation and clinical photography were performed at baseline and after 4 and 8 weeks. Additionally, a quality-of-life questionnaire was filled out by the test subjects at baseline and week 8. The subjects completed a self-assessment questionnaire on product properties after 4 and 8 weeks of product use.

RESULTS

Clinical assessments and subject response confirmed very good tolerability of the regimen, a statistically significant improvement in clinical grading for erythema and tactile roughness at weeks 4 and 8 and on telangiectasia at week 8 when compared to baseline scores. A statistically significant improvement in facial redness (a*) values, based on the L*a*b* colorimetric system, was determined at week 4 and 8 in comparison to baseline. No difference in corneometric measurement was detected at week 4 and 8 compared to baseline.

CONCLUSION

The skin care regimen was found to be highly compatible with the sensitive facial skin of patients with rosacea subtype I and effective in improving signs of rosacea. Therefore, the daily use of skin care products containing LicA and SymSitive(®) in patients with rosacea improves the overall skin appearance and the quality of life of these patients.

A fundamental investigation into aspects of the physiology and biochemistry of the stratum corneum in subjects with sensitive skin

BACKGROUND

Sensitive skin is a poorly understood skin condition. Defects in stratum corneum (SC) barrier function and/or extrasensory neuronal networks in the epidermis are believed to be involved in the problem.

OBJECTIVES

This study aimed to unravel the relationships between bleomycin hydrolase (BH) and calpain-1 (C-1), pyrrolidone carboxylic acid (PCA) levels, corneocyte maturation, transglutaminase (TG) and plasmin activities on the cheeks of subjects with sensitive skin.

METHODS

Forty-eight female Caucasian subjects, Fitzpatrick skin phototypes II-III, with self-perceived sensitive facial skin, were assessed and underwent a capsaicin reactivity test. Expert grading of skin condition was conducted as well as the measurement of transepidermal water loss (TEWL), skin capacitance, SC cohesion and SC integrity. BH, C-1 and plasmin activities were measured as well as PCA levels, plasmin and TG activity. Differential Nile red and involucrin immunostaining was performed to assess corneocyte maturation and size.

RESULTS

About 52% of the subjects reacted to capsaicin. There were no significant differences between the capsaicin-sensitive and non-capsaicin-sensitive subjects with reference to skin grading, TEWL, skin capacitance and SC cohesion. PCA levels and BH activity were lowest in the capsaicin-sensitive panel (P < 0.05) and were correlated in non-capsaicin-sensitive subjects (r = 0.72). The activity of TG was significantly lower (48%) in the capsaicin-sensitive subjects (P < 0.001) and their corneocytes were less mature and smaller (P ≤ 0.05). SC was estimated to be thinner (6.87 ± 0.28 vs. 8.68 ± 0.26 μm; P = 0.001) in the capsaicin-sensitive subjects with a corresponding shorter SC path length (83.2 ± 4.4 μm and 113.1 ± 4.5 μm; P = 0.001).

CONCLUSIONS

Despite the physiological similarities between the two groups of sensitive skin subjects, differences in their biochemistry were clearly evident. Lower levels of PCA, BH and TG activities together with a greater number of smaller and immature corneocytes indicate inferior SC maturation in the capsaicin-sensitive subjects. The reduced maturation of corneocytes and thinner SC likely contributes to a greater penetration of capsaicin and the associated increased skin sensitivity.