Sensitive skin: an overview

Sensitive skin is a condition of subjective cutaneous hyper‐reactivity to environmental factors. Subjects experiencing this condition report exaggerated reactions when their skin is in contact with cosmetics, soaps and sun screens, and they often report worsening after exposure to dry and cold climate. Although no sign of irritation is commonly detected, itching, burning, stinging and a tight sensation are constantly present. Generally substances that are not commonly considered irritants are involved in this abnormal response.Sensitive skin and subjective irritation are widespread but still far from being completely defined and understood. A correlation between sensitive skin and constitutional anomalies and/or other triggering factors such as occupational skin diseases or chronic exposure to irritants has been hypothesized. Recent findings suggest that higher sensitivity can be due to different mechanisms. Hyper‐reactors may have a thinner stratum corneum with a reduced corneocyte area causing a higher transcutaneous penetration of water‐soluble chemicals. Alterations in vanilloid receptors and changes in neuronal transmission have been described. Monitoring skin parameters such as barrier function, proclivity to irritation, corneocyte size and sensorial transmission can also be useful to identify regional differences in skin sensitivity.     

发用类、肤用清洁类化妆品的急性皮肤和眼刺激损害特点

分析发用类、肤用清洁类化妆品的急性皮肤刺激和急性眼刺激损害特点,了解其卫生安全状况。于2012年采用《化妆品卫生规范》(2007年版)中的急性皮肤刺激性实验和急性眼刺激性实验对发用类、肤用清洁类共计158种化妆品样品进行测试。两类受试化妆品显示出不同程度的急性皮肤刺激性和急性眼刺激性损害效应。发用类化妆品在实验中基本无皮肤刺激性损伤;肤用清洁类化妆品在实验中有少量的皮肤刺激性损伤,但大都为轻刺激性(31.0%),只有个别(3.8%)出现了皮肤红斑水肿的中刺激性损伤。发用类、肤用清洁类化妆品在急性眼刺激性实验中检出一定比例具有微刺激性及以上刺激性的样品,但引起的眼损伤都能够在观察期限内恢复。本次调查的所有化妆品中,洁面类、洗发类化妆品普遍具有急性眼刺激性和急性皮肤刺激性损害,需加强对化妆品的监督管理,进一步提升化妆品卫生安全水平,保障化妆品使用安全。     

Effects of topical gluco-oligosaccharide and collagen tripeptide F in the treatment of sensitive atopic skin

Sensitive skin is a dermatological problem of increasing incidence in western countries and is sometimes associated with atopic condition and bacterial sovrainfection. The purpose of this study is to evaluate in a double blind, randomized, placebo controlled trial the efficacy of gluco-oligosaccharide and collagen tripeptide F in controlling the signs and symptoms of sensitive atopic skin. Forty female subjects (age, 30–59 years) affected by non-lesional atopic sensitive skin entered the study. Skin sensitivity was determined by a dermatologist on the basis of medical history, stinging test, dermatological examination and a questionnaire. A treatment with the test products (active and placebo) was carried out for 4 weeks. Measurements and clinical evaluation were carried out at baseline and at the end of the study. The following objective parameters investigated were bacterial count, skin pH and colour, transepidermal water loss (TEWL), stratum corneum hydration, skin roughness and mechanical properties. Clinical assessment included also a scoring system for dryness, desquamation, irritation, erythema and papules. Significant differences were found in the active treated group when compared with the placebo and in particular for instrumental parameters of roughness ( P  < 0.02), volume ( P  < 0.01), TEWL ( P  < 0.02), erythema ( P  < 0.0006) and clinical parameters of dryness, desquamation and irritation ( P  < 0.001). Moisturization levels and skin colour improved significantly in both the active and placebo groups. In conclusion, the study shows that the modulation of bacterial proliferation and normalization of skin barrier properties and stratum corneum moisturization can improve the symptoms of sensitive skin.     

Significance of hair‐dye base‐induced sensory irritation

Oxidation hair ‐ dyes, which are the principal hair ‐ dyes, sometimes induce painful sensory irritation of the scalp caused by the combination of highly reactive substances, such as hydrogen peroxide and alkali agents. Although many cases of severe facial and scalp dermatitis have been reported following the use of hair ‐ dyes, sensory irritation caused by contact of the hair ‐ dye with the skin has not been reported clearly. In this study, we used a self‐assessment questionnaire to measure the sensory irritation in various regions of the body caused by two model hair‐dye bases that contained different amounts of alkali agents without dyes. Moreover, the occipital region was found as an alternative region of the scalp to test for sensory irritation of the hair‐dye bases. We used this region to evaluate the relationship of sensitivity with skin properties, such as trans‐epidermal water loss (TEWL), stratum corneum water content, sebum amount, surface temperature, current perception threshold (CPT), catalase activities in tape‐stripped skin and sensory irritation score with the model hair‐dye bases. The hair‐dye sensitive group showed higher TEWL, a lower sebum amount, a lower surface temperature and higher catalase activity than the insensitive group, and was similar to that of damaged skin. These results suggest that sensory irritation caused by hair ‐ dye could occur easily on the damaged dry scalp, as that caused by skin cosmetics reported previously.     

Cinnamic acid derivatives in cosmetics: current use and future prospects

Cinnamic acid derivatives are widely used in cosmetics and possess various functions. This group of compounds includes both naturally occurring and synthetic substances. On the basis of the Cosmetic Ingredient Database (CosIng) and available literature, this review summarizes their functions in cosmetics, including their physicochemical and biological properties as well as reported adverse effects. A perfuming function is typical of many derivatives of cinnamaldehyde, cinnamyl alcohol, dihydrocinnamyl alcohol and cinnamic acid itself; these substances are commonly used in cosmetics all over the world. Some of them show allergic and photoallergic potential, resulting in restrictions in maximum concentrations and/or a requirement to indicate the presence of some substances in the list of ingredients when their concentrations exceed certain fixed values in a cosmetic product. Another important function of cinnamic acid derivatives in cosmetics is UV protection. Ester derivatives such as ethylhexyl methoxycinnamate (octinoxate), isoamyl p‐methoxycinnamte (amiloxiate), octocrylene and cinoxate are used in cosmetics all over the world as UV filters. However, their maximum concentrations in cosmetic products are restricted due to their adverse effects, which include contact and a photocontact allergies, phototoxic contact dermatitis, contact dermatitis, estrogenic modulation and generation of reactive oxygen species. Other rarely utilized functions of cinnamic acid derivatives are as an antioxidant, in skin conditioning, hair conditioning, as a tonic and in antimicrobial activities. Moreover, some currently investigated natural and synthetic derivatives of cinnamic acid have shown skin lightening and anti‐ageing properties. Some of them may become new cosmetic ingredients in the future. In particular, 4‐hydroxycinnamic acid, which is currently indexed as a skin‐conditioning cosmetics ingredient, has been widely tested in vitro and in vivo as a new drug candidate for the treatment of hyperpigmentation.     

大鼠经皮电阻试验在化妆品安全性评价中的应用

目的 探讨大鼠经皮电阻试验在化妆品皮肤腐蚀性/刺激性评价中的应用。方法 依照我国《化妆品安全技术规范》(2015版)中体外皮肤腐蚀性大鼠经皮电阻试验方法, 分别以Wistar大鼠和SD大鼠对7种化学品和5种化妆品进行皮肤腐蚀性检测, 考察该方法在化妆品成品检验中的可行性。结果 两品系大鼠经皮电阻试验判定7种化学品和5种化妆品结论一致, 方法灵敏性100%, 特异性75%, 两品系大鼠判定结果均将异丙醇和十二烷基磺酸钠(20%)判定为假阳性。结论 大鼠经皮电阻试验方法可用于化妆品及其原料皮肤腐蚀性的初筛。     

Plant-based active photoprotectants for sunscreens

Excessive exposure to the sun's radiation is the major exogenous mediator of skin damage, which accelerates skin ageing and increases the risk of developing skin cancer. Compounds with photoprotectant activity are extremely useful for decreasing the effect of ultraviolet (UV) radiation on the skin; however, numerous sun filters, especially organic sunscreens, are allergenic. Therefore, the development of formulations containing plant extracts, which may be potentially safer, is extensively being explored. Plant-based cosmetics are commonly used to avoid skin ageing because they contain antioxidant agents that minimize free radical activity, and numerous studies have investigated the skin-protectant effects of related plant species. In addition to their antioxidant properties, plant-based cosmetics protect the skin against solar radiation because they contain polyphenols such as flavonoids and carotenoids. Therefore, this study aims to present a review of plant species commonly used in sunscreens to protect the skin against damage due to sunlight exposure.     

Squamometry: a tool to move from exaggerated to more and more realistic application conditions for comparing the skin compatibility of surfactant-based products

Squamometry consists of sampling the most superficial layers of the stratum corneum by means of a sticky tape firmly pressed onto the skin. Harvested cells are stained and the intensity of staining is related to the level of skin surface alterations caused by surfactant-based products. This method is extremely sensitive and the current study demonstrates that, thanks to squamometry, product mildness can now be compared without causing skin irritation due to exaggerated application conditions. In a 15 minute patch test, squamometry assessments ranked a series of surfactants as expected from their known irritation potential, without causing clinical signs of irritation. Similarly, the counter-irritant effect of amphoteric and nonionic surfactants on the irritation potential of anionic surfactants was evidenced. In a 30 minute patch test, shampoos were ranked by squamometry as they were in a classical Soap Chamber Test (48 hours of application). Finally, four hand dishwashing liquids were tested for one week by consumers according to a procedure similar to normal usage of the products, and were classified by squamometry as they were in a previous Soap Chamber Test. In conclusion, this study suggests that squamometry is able to predict the skin compatibility of surfactant-based products even after very short and realistic application times to volunteers' skin. Providing further validation, this technique could allow a move to test conditions much closer to the normal usage procedure of the products, to design test protocols much more respectful of panelists' skin condition, and to get information on product tolerance very quickly.     

The perception threshold measurement can be a useful tool for evaluation of sensitive skin

Sensitive skin is characterized by subjective symptoms that are hard to quantify. However, a neurobiological approach could improve our understanding of the nature of skin sensitivity. In this study, we measured the sensory perception of well-controlled electric currents on the skin that stimulated sensory nerve fibres such as the myelinated A fibre, A delta fibre and unmyelinated c-fibre. The sensory perception thresholds were obtained quantitatively from subjects with sensitive-prone skin and controls. Application of 0.075% capsaicin, known to stimulate the nociceptor c-fibre, was topically applied; then the sensory perception thresholds were measured to determine whether the exposure to nociceptive stimulation could affect the subsequent sensory perception. The results showed that the perception thresholds of skin sensitive-prone subjects were low for the c-fibre measurements at 5 Hz electric current stimulation. Furthermore, a wide variation in sensory perception was noted in the skin sensitive-prone subjects after topical application of capsaicin. In conclusion, the abnormal sensory perception in individuals with sensitive skin appears to be related to neurological instability, where c-fibre nociception plays a role. Thus, quantitative sensory perception threshold measurement was found to be a useful method for the identification of skin sensitive-prone subjects.     

The influence of alkane chain length on the skin irritation potential of 1,2-alkanediols

Several studies have reported that 1,2-alkanediols show increasing anti-microbial activity as their alkane chain length increases. However, there are no reports on the influence of alkane chain length on the skin irritation potential of 1,2-alkanediols. To investigate the influence of alkane chain length on the skin irritation potential of 1,2-alkanediols. The objective and subjective (sensory) skin irritation potentials of five 1,2-alkanediols - 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol and 1,2-decanediol - were evaluated. We also estimated percutaneous absorption by measuring in vitro skin penetration using a Franz diffusion cell system. Like anti-microbial activity, sensory irritation potential increased as alkane chain length increased, most likely due to increasing membrane interference and/or intrinsic toxicity of 1,2-alkanediols. 1,2-Hexanediol showed the lowest objective skin irritation potential, which increased when the alkane chain length decreased or increased. Furthermore, percutaneous absorption negatively correlated with the alkane chain length of 1,2-alkanediols. These results show that a lower skin absorption potential is not indicative of a low skin irritation potential. Our results suggest that the factors and processes involved in skin irritation potential are complex and that skin irritation potential is influenced by intrinsic toxicity and the potential for penetration or integration in the lipid bilayer.     

Odor and color of cosmetic products: correlations between subjective judgement and autonomous nervous system response

The color and odor of cosmetics have been shown to be crucial for affective states and able to influence autonomic responses. We report an original procedure to measure the effect on subjects of the color and odor of cosmetic products, and to quantify the correlation between objective (psychophysiological recording) and subjective (psychophysics) responses. Several cosmetic products (lipsticks and nail varnishes) of different colors (white, brown, red, orange, and pink) and odors (two per product) were presented. In a first step, autonomous parameters (skin conductance (SC) and heart rate (HR)) were recorded, and in the second step, subjects rated their sensations on subjective scales (overall appreciation, pleasantness, and emotional arousal). Results indicated that certain color and odor additives in cosmetics act on relaxation, excitation, perceived pleasantness, and emotional arousal. It was also found that certain colors, perceived as pleasant, decreased HR, and that the perception of an 'arousing' perfume significantly increased SC.     

Facial distribution of subcutaneous fat in women

Transparency of the skin is an important keyword that is frequently used in questionnaires related to the female skin condition and skin consciousness, as well as an index for 'before and after' comparisons of the effect of cosmetics. However, the concept of 'transparency' has not been concretely defined. In the present study, we investigated the importance of 'transparent skin' and the relationship between transparency and other expressions for skin condition comparing the young with middle-aged and elderly women. Furthermore, we also analyzed the correlation between the subjective assessment score of transparency of panels made by evaluators and the skin physiological parameters of those panels, and compared the difference of their relationship when the young and middle-aged and elderly women were employed as evaluators. Regarding the consciousness of the young women, the importance of 'transparent skin' was ranked in the top position while 'skin roughness' was the chief worry of the middle-aged and elderly women. On the other hand, both age groups indicated that transparent skin is a complex concept composed of skin texture, color, and moisture. Analysis of the relationship between the subjective assessment and the skin physiological parameters showed that the uneven dispersion of b in the skin color (standard deviation), the water content of stratum corneum, and the skin surface configuration (depth of furrows, amount of furrows) closely correlated with the judgment of skin transparency in the young group, in contrast to the uneven dispersion of L and a in the skin color (standard deviation) in the middle-aged and elderly women. These results suggest that there may be no differences between the different age groups in the linguistic concept of transparency, while there may be differences in the physiological characteristics of skin that are utilized in making the judgment of transparency.     

聚二甲基硅氧烷应用及安全性评估概况

聚二甲基硅氧烷(PDMS)广泛用于食品添加剂、日用化妆品、医疗器材等.目前的研究认为PDMS基本不被人的皮肤与胃肠所吸收,几乎无急性毒性,对皮肤基本无刺激作用,对眼部有刺激作用,可引起轻度结膜炎或红膜炎.无证据表明PDMS有致畸、致癌性及遗传毒性.有理由认为,PDMS在现有的正常使用情况下,不会引起健康危害.     

Anti-inflammatory activity of Pseudopterosins by laser doppler blood flow evaluation

IFSCC Magazines , 12 (2009) (1) 25–30
Approximately 40% of the population (all skin categories and phototypes) complain of sensitive skin. Sensitive skin is healthy but overresponsive, meaning it reacts faster and more intensely to several parameters including environmental factors such as temperature changes and the sun, use of cosmetic products, and certain medicines. It experiences discomfort, tingling, burning and intolerance to certain types of products, a condition referred to as neurosensitivity characterized by a lower threshold of tolerance. Currently, all of the causes are not known but an increase in the permeability of the stratum corneum and an exaggeration of the nerve response are considered to be involved in the phenomenon of sensitive skin. Lifestyle factors including tobacco, alcohol, stress, fatigue and emotions also have an effect. A new synthetic tetrapeptide, N -acetyl- L -tyrosyl- L -prolyl- L -phenylalanyl- L -phenylalaninamide (Ac-YPFF-NH2), mimicking a natural opioid peptide was developed with the aim to decrease skin nerve ending stimulation. This tetrapeptide was demonstrated in vitro to reduce cutaneous overreactivity by decreasing release of calcitonin gene-related peptide from sensory neurons via an agonist effect on the μ opioid receptors and in vivo to improve the comfort of sensitive skin by decreasing unpleasant sensations and pain induced by heat and capsaicin. This tetrapeptide targeting an exaggerated nerve response helps to relieve sensitive skin by normalizing the tolerance threshold for environmental factors or certain topically applied uncomfortable products or skincare treatments.
Keywords:  Calcitonin gene-related peptide, μ opioid receptor, nerve endings, peptide, sensitive skin     

The influence of a cream containing 20% glycerin and its vehicle on skin barrier properties

Glycerin is widely used in cosmetics and well as in pharmaceutical formulations, mainly as humectant. In vitro studies have shown glycerin to prevent crystallization of stratum corneum model lipid mixture at low room humidity. Whether this may affect the skin barrier function during repeated application of glycerin in a cream base to normal skin is not known. Therefore, the influence of a cream containing 20% glycerin was compared with its placebo cream in a bilateral, double-blind study on 17 healthy volunteers. The effect was evaluated as influence on hydration with a corneometer and on skin barrier function. Skin barrier function was assessed as permeability to water with an evaporimeter (transepidermal water loss; TEWL) and as sensitivity to an irritating surfactant by measuring the biological response (measured as TEWL and skin blood flow). Ten days treatment of normal skin with 20% glycerin significantly increased skin corneometer values, indicating an increased hydration. However, our study failed to show an influence of glycerin on human skin, in terms of TEWL and skin sensitivity to SLS-induced irritation.     

Quantification of glycolic acid in cosmetic products using reversed phase high performance liquid chromatography

Many cosmetics contain keratolytic hydroxy acids to correct the effects of photoageing on human skin. Although methods exist for quantifying the alpha-hydroxy acid, glycolic acid in aqueous media, accurate methods for quantification in mixed hydrophobic and aqueous cosmetic creams and lotions are lacking. Glycolic acid was extracted from cosmetics using aqueous tetrahydrofuran (THF), separated with strong-anion exchange cartridges, and quantified by high performance liquid chromatography (HPLC) with UV-VIS detection without the paired-ion reagents. In a recovery experiment, the mean accuracy of the method was 100.6%. The dynamic range of the method allows for the detection of glycolic acid at concentrations used in over-the-counter cosmetics.     

The use of transepidermal water loss to measure and predict the irritation response to surfactants

The ability of baseline transepidermal water loss (TEWL) measurements to predict the response of healthy subjects to a standard soap chamber irritation insult was evaluated. Chambers containing surfactant solutions were applied to the forearms of normal volunteers for five consecutive days. TEWL was measured using a Servo Med Evaporimeter. TEWL measurements were made prior to the first application of the chambers and following the removal of the second set of chambers (the afternoon of Day 1). The correlation between the TEWL values obtained on Day 1 and the subjective evaluation of irritation resulting from the application of two different toilet soaps was statistically significant. This result indicates that damage to the skin is reflected by an increase in TEWL. Interestingly, there was also a statistically significant correlation between TEWL values obtained on the untreated skin at Time 0 and the five-day average irritation score for these two cleansing products. The results of this study indicate that a high baseline TEWL value may be predictive of a high susceptibility to soap irritation as measured by the chamber test.
Le role des pertes en eau transepidermique pour mesurer et prevoir l'irritation due aux tensio-actifs     

No. 2Vol. 42, No. 4, pp. 289–296, 2008An influence of cosmetic formula on thermal characteristics and its relationship with the sensation of freshness during application

Polyglycerol fatty acid esters (PGFE) , a food grade emulsifier has been used in cosmetic products in recent years due to its safety and low stimulation of skin. Cosmetic formulation containing CoQ1O to provide a stable and clear pre-paration is difficult because it has a high crystalline property. We have tried the development of CoQ10-soluble pre-paration with PGFE applied for cosmetics. The present study is summarized as follows: This CoQ10-soluble pre-paration has a bicontinuous microemulsion structure that provides high solubilization capacity and thermodynamic stability. Cosmetics using this CoQ1O soluble pre-paration tend to improve the skin permeability and also to involve the change in skin conditions (moisturization and elasticity), compared to the non-bicontinuous microemulsion pre-paration.
Keywords:  coenzyme Q10, solubilization, bicontinuous, microemulsion, polyglycerol fatty acid ester, cosmetics, food, emulsifier, safety, low stimulation, skin, moisturization, elasticity     

Relationship between perceived softness of bilayered skin models and their mechanical properties measured with a dual‐sensor probe

The development of a sensor system that can predict the subjective softness of human skin is an important goal for the cosmetics industry. Here, we first carried out a subjective softness evaluation test using 65 skin models consisting of polyurethane bilayers with different thickness of the superficial layer and different degree of cross‐polymerization of the basal layer. The results showed that perceived softness was dependent on the mechanical properties of both the superficial and basal layers. Then, we used a recently developed tactile sensor system composed of a piezoelectric tactile sensor and a load cell to measure mechanical softness parameters of the superficial layer and the whole model, respectively. Statistical analysis showed that the data obtained from these two sensors were well correlated with the perceived softness of the prepared models. These results suggest that it may be feasible to predict the subjective softness of human skin in vivo from non‐invasive mechanical softness measurements of the superficial skin layer and whole skin obtained with our new dual‐probe sensor system.