Triggering factors in sensitive skin from the worldwide patients’ point of view: a systematic literature review and meta‐analysis

Road-traffic-related air pollution contributes to skin barrier alteration and growth defect of sensory neurons

The effects of air pollution on health are gaining increasing research interest with limited data on skin alterations available. It was suggested that air pollution is a trigger factor for sensitive skin (SS). However, this data was based on surveys with a lack of experimental data. SS is related to altered skin nerve endings and cutaneous neurogenic inflammation. TTe present study was to assess the in vitro effect of particulate matter (PM) on epidermis and nerve ending homeostasis. PM samples were collected according to a validated protocol. Reconstructed human epidermis (RHE, Episkin®) was exposed to PM and subsequently the supernatants were transferred to a culture of PC12 cells differentiated into sensory neurons (SN). Cell viability, axonal growth and neuropeptide-release were measured. The modulation of the expression of different inflammatory, keratinocytes differentiation and neurites growth markers was assessed. PM samples contained a high proportion of particles with a size below 1 μm and a complex chemical composition. Transcriptomic and immunohistochemical analyses revealed that PM altered keratinocytes terminal differentiation and induced an inflammatory response. While viability and functionality of the SN were not modified, their outgrowth was significantly decreased after incubation with PM-exposed Episkin® supernatants. This was closely related to the modification of nerve growth factor/semaphorin 3A balance. This study showed that air pollutants have negative effects on keratinocytes and sensory nerve endings including inflammatory responses. These effects are probably involved in the SS pathophysiology and might be involved in inflammatory skin disorders.

A review of factors influencing sensitive skin: an emphasis on built environment characteristics

Background

Sensitive skin (SS) is a condition characterized by hyperreactivity. Impacting around 37 percent of the worldwide population and exerting an influence on the quality of life for affected individuals. Its prevalence rate has increased due to factors such as elevating stress levels and deteriorating environmental conditions. The exposome factors influencing SS have extended from demographic, biological attributes, and lifestyle to external environments. Built environments (BEs) have demonstrated as root drivers for changes in behaviors and environmental exposure which have the potential to trigger SS, but the review of the associations between BEs and SS is currently lacking.

Objective

This review aims to achieve two primary objectives: (1) Examine exposome factors that exert influence on SS at the individual and environmental levels. (2) Develop a theoretical framework that establishes a connection between BEs and SS, thereby offering valuable insights into the impact of the built environment on this condition.

Methods

An extensive literature search was carried out across multiple fields, including sociology, epidemiology, basic medicine, clinical medicine, and environmental research, with a focus on SS. To identify pertinent references, renowned databases such as PubMed, Web of Science, and CNKI were utilized.

Results

SS is the outcome of interactions between individual attributes and environmental factors. These influencing factors can be categorized into five distinct classes: (1) demographic and socioeconomic characteristics including age, gender, and race; (2) physiological and biological attributes such as emotional changes, skin types, sleep disorders, and menstrual cycles in women; (3) behavioral factors, such as spicy diet, cosmetic use, alcohol consumption, and physical exercise; (4) natural environmental features, including climate conditions and air pollution; (5) built environmental features such as population density, green space availability, road network density, and access to public transportation, also have the potential to affect the condition.

Conclusion

The importance of interdisciplinary integration lies in its ability to ascertain whether and how BEs are impacting SS. By elucidating the role of BEs in conjunction with other factors in the onset of SS, we can provide guidance for future research endeavors and the formulation of interventions aimed at mitigating the prevalence of SS.

Sensitive Scalp and Trichodynia: Epidemiology, Etiopathogenesis, Diagnosis, and Management

Sensitive scalp (SSc) is considered a sensitive skin on the scalp, with its particularities. Although it is not rare in the dermatological practice and the term is commonly present in personal care products, this entity is poorly investigated in the medical literature. The etiopathogenesis is still uncertain, and the sensitivity may be associated with hair loss. Clinical manifestations are subjective symptoms of pruritus, burning, pain, pricking, and/or trichodynia, often with scalp erythema. SSc can be triggered by several factors (endogenous or exogenous). The diagnosis is guided by the anamnesis, and there are still no specific trichoscopic features. Trigeminal trophic syndrome and postherpetic neuralgia are the main differential diagnosis to be considered. We organized the therapeutical approach in three steps: scalp care, topical and systemic treatment.

Clinical study of a spray containing birch juice for repairing sensitive skin

Sensitive skin is described as an unpleasant sensory response to a stimulus that should not cause a sensation. Sensitive skin affects an increasing proportion of the population. Sixty-seven participants who tested positive to lactic acid sting test were recruited and randomized into two groups to observe the clinical efficacy and safety of a new birch juice spray for repairing sensitive skin. One group used test spray A, while the other group used spray B as a control. Both groups were sprayed six times daily for 28 days. Noninvasive testing instruments were used to measure stratum corneum hydration, sebum content, transepidermal water loss rates, skin blood perfusion and current perception threshold before and after using spray. Facial images were captured by VISIA-CR, and the image analysis program (Image-Pro Plus) was used to analyze these to obtain the redness value of the facial skin. Moreover, lactic acid sting test scores and participants' self-assessments were also performed at baseline, week 2 and week 4. Both sprays A and B significantly decreased the lactic acid sting test score, transepidermal water loss rates, skin blood perfusion, and redness, while increasing the stratum corneum hydration. Compared to spray B, spray A increased sensory nerve thresholds at 5 Hz and decreased the transepidermal water loss rates, skin blood perfusion, and lactic acid sting test score. Sprays containing birch juice improved cutaneous biophysical properties in participants with sensitive skin.

Effects of a Postbiotic Saccharomyces and Lactobacillus Ferment Complex on the Scalp Microbiome of Chinese Women with Sensitive Scalp Syndrome

Introduction

Sensitive scalp is one of the most frequent complaints related to sensitive skin syndrome, characterized by unpleasant sensory reactions in the absence of visible signs of inflammation. In this study, the effects of topical application of postbiotic Himalaya-derived Saccharomyces and Lactobacillus ferment complex (SLFC) on the bacterial and fungal scalp microbiome at the taxonomic level and alleviation of sensitive skin syndrome were investigated.

Methods

Firstly, healthy female participants (aged 30-45) were classified into a healthy scalp group and a sensitive scalp group based on the questionnaire. Thereafter, topical application of SLFC on sensitive scalp as well as scalp microbiome was evaluated, with the difference in the distribution of microbial taxa between healthy and sensitive scalp communities was assessed using 16S rRNA and ITS1 sequencing analysis. In addition, the effect of SLFC on scalp microbiome at the species level for Cutibacterium acnes, Staphylococcus epidermidis, and Malassezia restricta was evaluated by the qPCR assessment.

Results

After treatment with SLFC for 28 days, the abundance of Staphylococcus, Lawsonella, and Fusarium in the sensitive scalp group was highly significantly increased (p < 0.001), while the abundance of Cutibacterium and Malassezia was highly significantly decreased (p < 0.001). Furthermore, the self-assessment questionnaire indicated a syndrome alleviation effect of 100% after 28 days with a twice-daily application of the SLFC.

Discussion

The obtained results would help to better understand the microbial community of the sensitive scalp and provide useful information on utilization of SLFC for maintaining a healthy scalp and modulating the scalp microbiome.

Ambient temperature exposure and risk of outpatient visits for dermatologic diseases in Xinxiang, China: a time-series analysis

The effect of ambient temperature on dermatologic diseases has received widespread attention. Previous studies have shown that ambient temperature might affect specific dermatologic diseases, but results were inconsistent. This study aims to assess the short-term effect of ambient temperature on outpatient visits due to dermatologic diseases (DMs) in Xinxiang, China. Daily DMs outpatient visits, mean temperature, mean relative humidity, and air pollution data of Xinxiang were retrieved from January 1, 2015, to December 31, 2018. A distributed lag nonlinear model (DLNM) was applied to analyze the effect of ambient temperature on DMs outpatients. We controlled several potential confounding factors such as the long-term trend, public holiday, day of the week, humidity, and air pollutants (NO₂, PM_2.5). Finally, two more stratification analysis was conducted by age and gender. A total of 164,270 outpatients of DMs were enrolled during our study, and the daily mean visits were 113. The estimated effect of temperature on DMs was nonlinear. Heat temperature would exacerbate outpatients of dermatologic diseases. With a reference median temperature (17 °C), the effect of temperature on DMs was most pronounced at lag0-14; exposure to heat (32 °C, 99th) was associated with 1.565 (95% CI: 1.266-1.934) increased risk of outpatients for DMs. Stratification analysis showed that citizens of young ages were susceptive to heat; both genders had a similar relationship between temperature and DMs risk. This study highlights that ambient temperature was associated with DMs outpatients; heat temperature might aggravate DMs risk. The health hazards of heat temperature required more attention, and more effective prevention measurements should be designed and implemented to curb global warming.

Sensitive Skin Syndrome: A Low-Noise Small-Fiber Neuropathy Related to Environmental Factors?

Background and Objectives

Patients frequently complain of mild, transient, unpleasant skin sensations that cannot be diagnosed as common neuropathies. Dermatologists have termed these symptoms “sensitive skin syndrome.” This narrative review was performed for a better knowledge by other specialists.

Databases and Data Treatment

Publications on pain in sensitive skin syndrome were obtained from PubMed.

Results

There is a growing body of data supporting the concept that sensitive skin is a type of small-fiber neuropathy. The arguments are based on clinical data, a decrease in intra-epidermal nerve fiber density, quantitative sensory testing abnormalities and an association with irritable bowel syndrome and sensitive eyes. Sensitive skin is triggered by environmental factors. Sensitive skin is a frequent condition, with a lifetime prevalence of ~50% according to self-reports.

Conclusions

Mild levels of skin pain or itch are frequently experienced by patients, who rarely report them. There is a need for a better knowledge of sensitive skin because it can be the first level of small-fiber neuropathies.

Interest in Micellar Solution to Reduce Unpleasant Skin Sensations

Introduction

The results from the “Objectifs Peau” project showed that approximately 30% of the French population complains of an unpleasant skin sensation at least once a day. Itching was the most frequent complaint (32%), followed by tingling (18.9%) and burning sensation (5.6%), which impact an individual’s daily life. These sensations could be identified, as they were either isolated or associated with each other. The aim of this study was to evaluate the use of micellar solution to reduce these sensations, especially on sensitive skin.

Methodology

A questionnaire was administered at Day 0 (D0), D2, D14, and D28 using a mobile phone application to individuals applying micellar solution (Sensibio H2O, Laboratoire Bioderma, NAOS) who spontaneously used micellar solution for sensitive skin and/or spontaneously consulted a health professional. Itching, tightness, tingling and burning sensations were evaluated by means of frequencies (never, rarely, sometimes, often or constantly) at D0, D2, D14 and D28. Responses from the questionnaire were rated (never=0, rarely=1, sometimes=2, often=3 or constantly=4) and allowed us to obtain an overall “unpleasant sensations” score, where a higher score corresponded to a higher degree of unpleasant sensations.

Results

In total, 400 evaluable individuals participated in the study (97% female, average age 38.5±13 years, 82% reported sensitive skin). The “unpleasant sensations” score improved from D2 and continued significantly on D14 and D28. The improvement rates were 47.7%, 57.9% and 62.7% at D2, D14 and D28, respectively, compared to D0. The percentages of improvement at D2, D14 and D28 were 83.2% (95% CI: 79.26; 87.21), 87.54% (95% CI: 84.01; 91.06) and 90% (95% CI: 87.06; 92.94), respectively, compared to D0.

Conclusion

The improvement in the reduction of unpleasant sensations was observed as early as 2 days after using micellar solution and increased over time. The use of this type of micellar solution, especially on sensitive skin, and the guidance of health professionals (dermatologists and pharmacists) may help to reduce the impact of unpleasant skin sensations.

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.

Clinical and Instrumental Exploration of Sensitive Skin in a Pediatric Population

Studies on sensitive skin pathophysiology in infants are challenging because most assessment methods require self-reporting of signs. In this study, we aimed to identify and characterize sensitive skin in children for the first time. A newly developed parent-reported questionnaire was used to recruit children with sensitive skin. This questionnaire was also tested on an adult group. Hydration, transepidermal water loss (TEWL), and inflammatory markers (cytokines, and polyunsaturated fatty acids (PUFAs)) were quantified. A total of 77 children and 20 adults (33 and 10 with sensitive skin, respectively) were recruited. The groups with sensitive skin had more clinical signs of skin dryness. Skin hydration was lower in children in the sensitive compared with the nonsensitive skin group. TEWL levels were similar between sensitive and nonsensitive subjects in both infant and adult groups. Sensitive skin exhibited higher levels of cytokines and proinflammatory PUFAs as well as lower levels of anti-inflammatory PUFAs. Sensitive skin syndrome was associated with normal skin barrier function but lower hydration in infants and children. The higher levels of proinflammatory markers suggest that sensitive skin is associated with low-level inflammation. It is hypothesized, for the first time, that PUFAs are involved in sensitive skin syndrome in infants.

Demodex infestation as a cause of sensitive skin in a dermatology outpatient clinic

BACKGROUND

Sensitive skin is subjective cutaneous hyperreactivity to environmental factors. Demodicosis is a skin disorder caused by Demodex mites. There may be a link between demodicosis and sensitive skin.

AIM

This study aimed to examine facial Demodex mites density and other factors associated with sensitive skin in patients.

METHODS AND METHODS

A total of 349 randomly selected patients presented to the dermatology department. The research data were collected using a questionnaire form that included the participants' sociodemographic and lifestyle characteristics, a sensitive skin questionnaire, the Dermatology Life Quality Index (DLQI), and European Health Interview Survey (EHIS). Patients underwent standardized superficial skin surface biopsy of 4 areas of the face. D. folliculorum count greater than 5 mites/cm² was considered positive.

RESULTS

In relation to Demodex, there was an increase in skin sensitivity with higher Demodex density (p = 0.04). There was a statistically significant, weak positive correlation between skin sensitivity and DLQI score (r = 0.33, p = 0.00), and there was also a significant but very weak negative correlation between skin sensitivity and EUROHIS (r = -0.164, p = 0.002). Skin sensitivity was more common in patients with a concomitant dermatological disease (p = 0.01) and increased with more frequent cosmetic use (p = 0.00).

CONCLUSION

Alongside other risk factors, for the patients presenting with complaints of sensitive skin, investigating Demodex population density may help alleviate sensitive skin symptoms with appropriate therapies and preventive measures.

Sensitive Scalp: A Possible Association With the Use of Hair Conditioners

A sensitive scalp is defined by the occurrence of unpleasant sensations (tingling, burning, pain, pruritus) triggered by stimuli that should not cause such sensations. Environmental factors, particularly cosmetics, can be triggering factors. The aims of this study were to assess hair cosmetic product consumption in subjects with sensitive scalp and to perform a clinical evaluation of sensitive scalp. After a dermatological examination, women between the ages of 18 and 65 years with or without a sensitive scalp completed different questionnaires. Their use of hair cosmetics (frequency, amount per application) was recorded. A total of 160 women with a mean age of 41 years were included. Twenty-seven subjects presented with seborrheic dermatitis or psoriasis, so only 133 were included in the analysis. Five percent of the subjects declared they had a very sensitive scalp, 25% had a sensitive scalp, 38% had a slightly sensitive scalp, and 32% had a scalp that was not sensitive. The mean sensitive scalp score (3S) score was 3.7 ± 1.6 in the very sensitive scalp group, 3.6 ± 2.1 in the sensitive group, 1.2 ± 1.2 in the slightly sensitive group and 0.1 ± 0.4 in the non-sensitive group. Two groups were analyzed: the 56 subjects with a sensitive scalp (3S ≥ 2 score) and the 56 subjects with a null 3S score. In the sensitive scalp group, 89% suffered from itch, and 45% suffered from tingling. No parameter (hormonal status, smoking, age, phototype, BMI) was associated with the 3S score. No differences in the exposure to shampoos and masks between the two groups were noted. The exposure to hair conditioners was significantly higher in the sensitive scalp group than in the group without sensitive scalp. Itch is the main symptom of a sensitive scalp. The frequency of a sensitive scalp was lower than that previously described when the subjects with scalp dermatosis were excluded. The amount of hair conditioners used was significantly higher in subjects with sensitive scalp than in those without sensitive scalp, suggesting a possible link.

Relationship between sensitive skin and sleep disorders, fatigue, dust, sweating, food, tobacco consumption or female hormonal changes: Results from a worldwide survey of 10 743 individuals

BACKGROUND

Sensitive skin is related to environmental factors.

OBJECTIVES

We aimed to investigate the roles of poorly known associated and triggering factors on sensitive skin in a large global population.

METHODS

A survey was administrated to a representative sample of the adult population aged 18-75 years in five different countries (Brazil, China, France Russia, and the United States). All participants answered a web-based questionnaire on sociodemographic characteristics, sensitive skin and environmental factors.

RESULTS

Among the 10 743 included individuals (5285 men and 5458 women), 48.2% declared that they had sensitive skin. The group with sensitive skin reported significant increases in fatigue, dust or sweating and to a lesser extent food or tobacco consumption. The members of this group also declared that they experienced more sleep disorders than individuals without sensitive skin. Sensitive skin was very frequent in pregnant women, women with painful menstruations or women using contraceptive pills.

CONCLUSIONS

This large cohort study identified new factors, including female hormonal status, fatigue, sleep disorders and food, associated with sensitive skin. These associations suggest that sensitive skin is not restricted to an epidermal disorder but may be included in a larger context. The identified factors are potential upstream drivers of neurogenic inflammation in sensitive skin.

The 21-day cumulative irritation assay in man: a half-century summary and re-evaluation

The 21-day cumulative irritation test (21-day CIT) has been widely used in dermatopharmacology and dermatotoxicology to assess the irritation potential of topical products. Since described by Lanman in 1968, it has been modified, shortened, re-evaluated, and statistically analysed by multiple groups of authors. As the assay has been recommended in FDA draft guidance, we bring subsequent experience to date. The shorter 14-day version is commonly used and may be as adequate as the 21-day application when used to discriminate between moderate to strong irritants. While previous authors stopped the test when subjects experienced an irritation score of 3 or more, the FDA suggested moving the test to another anatomical site to complete in 21 days. This approach avoids assumptions, thus may be more accurate to quantify skin irritation. As the scoring is based on visual grading, the 21-day CIT also does not account for sensory irritation. Therefore, future studies need to propose a way to evaluate the sensation objectively in dermatological product development.

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.

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.