Sensitive skin: mechanisms and diagnosis

Sensitive skin is a condition of subjective cutaneous hyperreactivity to environmental factors. Subjects experiencing this condition report exaggerated reactions when their skin is in contact with cosmetics, soaps and sunscreens, 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. They include many ingredients of cosmetics such as: dimethyl sulfoxide, benzoyl peroxide preparations, salicylic acid, propylene glycol, amyldimethylaminobenzoic acid and 2-ethoxyethyl methoxycinnamate. Sensitive skin and subjective irritation are widespread but still far from being completely defined and understood. The aim of this paper is to summarize the relevant literature in order to elucidate the underlying mechanisms of sensitive skin and the best testing methodologies for investigation of sensitive skin.     

植物发酵活性物在美妆中应用研究进展

植物尤其是药用植物蕴涵着极其多样化的活性物质如多糖、多肽、黄酮、多酚、氨基酸等,其储存的含碳物占生物体含碳物的80%,在化妆品中具有广阔应用前景。但天然植物原材料中有效成分相对较低、传统提取不充分,甚至会有一些毒副作用成分,影响了其在化妆品原料中的应用。利用微生物发酵植物原料或提取物可以解决这些问题,可以促进活性物释放、富集或转化生成新的活性物、增强并拓展功效、降低毒副作用。植物发酵活性物具有抗菌、美白、抗氧化、抗炎、促进胶原再生等多重功效,在美妆产品中具有广阔应用前景。     

Anti-irritant potential of cosmetic raw materials and formulations

The investigation studied the anti-irritant potential of several substances commonly employed in cosmetic formulations as basic components of the emulsion or as active ingredients, and evaluated the effect of the emulsifier. Five different emulsions were made irritating by addition of croton oil, in sufficient quantity to provoke a clearly adverse reaction in the rabbit, i.e. primary cutaneous irritation index (PII) close to 2. The PII was determined according to the official French methods by applying to symmetrical areas of the back, the irritant base as control and the same base containing the test substance. Fifty-five ingredients were evaluated: gelling agents, plant extracts, molecules defined as healing, anti-inflammatory substances or anaesthesic compounds, etc. The test substances were added to the emulsion at concentrations close to the ones generally found in cosmetics. The qualitative and the quantitative composition of the oil phase was similar for each emulsion.
Several gelling agents, thickeners and polymers which notably reduce skin contact with an irritant, gave good results. Some of the usual healing, anti-inflammatory, local anaesthesic compounds gave the expected results. Some ingredients, though well known, were ineffective. The type of emulsifier, by modifying cutaneous penetration and bio-availability of the active ingredients, may play an important role.
Le potential anti-irritant de constituants de base et compositions cosmétiques     

The function of polyglyceryl erucate/isostearate/ricinoleate

Today, it is said that the formula design of cosmetics from ingredients of plant origin is an indispensable way and trend. From this consideration, cosmetic materials made from animal and synthetic petroleum ingredients are becoming less usable. Instead, cosmetic materials are designed from ingredients of plant origin and many and various botanical ingredients are being developed. Lanolin, which is one of the animal-based ingredients, is said to have ideal functions as a cosmetic oil, and it has been used in many fields such as make-up cosmetics as well as hair and skin care products for a long time. However, unfortunately, lanolin is an animal-based ingredient; therefore, the development of a botanical ingredient to replace lanolin was desired. Polyglyceryl-8 decaerucate/isostearate/ricinoleate, which we have developed, is an ester oil originating from plants and has an equivalent or higher function than lanolin. We have confirmed that our developed ester oil has various excellent characteristics such as a water-holding capability 2.5 times higher than that of lanolin, high air permeability, moisture keeping in dermal layers, protection of hair from changes in external environmental humidity, and excellent gloss and excellent dispersability of pigments. Thus, this newly developed ester oil is expected to be a promising new botanical cosmetic ingredient which can be applied in various fields.     

Polyphenols as active ingredients for cosmetic products

Polyphenols are secondary plant metabolites with antioxidant, anti‐inflammatory and anti‐microbial activity. They are ubiquitously distributed in the plant kingdom; high amounts contain, for example, green tea and grape seeds. Polyphenolic extracts are attractive ingredients for cosmetics and pharmacy due to their beneficial biological properties. This review summarizes the effects of polyphenols in the context of anti‐ageing activity. We have explored in vitro studies, which investigate antioxidant activity, inhibition of dermal proteases and photoprotective activity, mostly studied using dermal fibroblasts or epidermal keratinocytes cell lines. Possible negative effects of polyphenols were also discussed. Further, some physicochemical aspects, namely the possible interactions with emulsifiers and the influence of the cosmetic formulation on the skin delivery, were reported. Finally, few clinical studies, which cover the anti‐ageing action of polyphenols on the skin after topical application, were reviewed.     

Infant skin physiology and development during the first years of life: a review of recent findings based on in vivo studies

Infant skin is often presented as the cosmetic ideal for adults. However, compared to adult skin it seems to be more prone to develop certain pathological conditions, such as atopic dermatitis and irritant contact dermatitis. Therefore, understanding the physiology of healthy infant skin as a point of reference is of interest both from the cosmetic as well as from the clinical point of view. Clinical research on healthy infants is, however, limited because of ethical considerations of using invasive methods and therefore until recently data has been scarce. Technical innovations and the availability of non‐invasive in vivo techniques, such as evaporimetry, electrical impedance measurement, in vivo video and confocal microscopy, and in vivo fibre‐optic based spectroscopy, opened up the field of in vivo infant skin physiology research. Studies incorporating such methods have demonstrated that compared to adult, infant skin continues to develop during the first years of life. Specifically, infant skin appears to have thinner epidermis and stratum corneum (SC) as well as smaller corneocytes at least until the second year of life. The water‐handling properties are not fully developed before the end of the first year and infant SC contains more water and less amounts of natural moisturizing factors. Such findings re‐evaluate the old notions that skin is fully matured at birth. Armed with this knowledge, we are in a position not only to better understand infant dermatological conditions but also to design better skin care products respecting the distinct qualities of infant skin.     

Shear viscosity of concentrated spherical silica suspension – effect of polymethylsiloxane surface treatment

Common cosmetic dermatitis is composed of mainly chronic irritant contact dermatitis, allergic contact dermatitis and pigmented cosmetic dermatitis. Special types include atopic contact dermatitis due to cosmetics, complication of corticosteroid dermatosis, and eyelid dermatitis. Common cosmetic sensitizers are various fragrances, pigments and base components. The best treatment to stop the recrudescence of cosmetic dermatitis is to perform patch testing to discover causative allergens for the patients, so that allergen control becomes possible later. It has been the only effective method to perfectly cure the disastrous pigmented cosmetic dermatitis with Mongoloids in the past. The avoidance of very allergenic fragrances (class A fragrances in the table) and two pigments, D&C Red No.31 and Yellow No.11 is essential to reduce cosmetic dermatitis of the consumers. The introduction of guidelines to avoid strong sensitizers is recommended. Recently, eyelid dermatitis due to allergy or irritation has been common and rubbing itchy eyelids has led to blindness due to retinal abrasion. Adding various plant components seemed to have increased the irritation, and it is better to be avoided hereafter.     

Antioxidants for improved skin appearance: Intracellular mechanism,challenges and future strategies

Recent advances in molecular and biochemical processes relevant to the skincare field have led to the development of novel ingredients based on antioxidants that can improve skin health and youthfulness. Considering the plethora of such antioxidants and the many implications for the skin's appearance, this review focuses on describing the critical aspects of antioxidants, including cosmetic functions, intracellular mechanisms and challenges. In particular, specialized substances are suggested for the treatment of each skin condition, such as skin ageing, skin dehydration and skin hyperpigmentation, which treatments can maximize effectiveness and avoid side effects during skin care processes. In addition, this review proposes advanced strategies that either already exists in the cosmetic market or should be developed to improve and optimize cosmetic’ beneficial effects.     

Antibacterial activity and mechanism of cinnamic acid and chlorogenic acid against Alicyclobacillus acidoterrestris vegetative cells in apple juice

The aim of this study was to investigate the antibacterial activity and mechanism of cinnamic acid and chlorogenic acid against Alicyclobacillus acidoterrestris. Minimum inhibitory concentrations of cinnamic acid and chlorogenic acid were 0.375 and 2.0 mg mL⁻¹, and the minimum bactericidal concentrations were 0.50 and 4.0 mg mL⁻¹, respectively. The apple juice ingredients had little influence on the inactivation of A. acidoterrestris. After treatment with cinnamic acid and chlorogenic acid, the morphology of A. acidoterrestris cells were severely destroyed; the leakage of nucleic acids and proteins increased significantly. SDS-PAGE investigation of bacterial proteins proved that the loss of soluble proteins was obvious as well. These results demonstrated that cinnamic acid and chlorogenic acid exerted their antibacterial activity mainly by an action mode of membrane disruption. This study provides an alternative method for the control of A. acidoterrestris-related spoilage in the fruit juice/beverage industry.     

A novel volumetric method for quantitation of titanium dioxide in cosmetics

Nowadays there are many sun‐protection cosmetics incorporating organic or inorganic UV filters as active ingredients. Chemically stable inorganic sunscreen agents, usually metal oxides, are widely employed in high‐SPF (sun protection factor) products. Titanium dioxide is one of the most frequently used inorganic UV filters. It has been used as a pigment for a long period of cosmetic history. With the development of micronization techniques, it has become possible to incorporate titanium dioxide in sunscreen formulations without the previous whitening effect, and hence its use in cosmetics has become an important research topic. However, there are very few works related to quantitation of titanium dioxide in sunscreen products. In this research, we analysed the amounts of titanium dioxide in sunscreen cosmetics by adapting redox titration, reduction of Ti(IV) to Ti(III), and reoxidation to Ti(IV). After calcification of other organic ingredients of cosmetics, titanium dioxide is dissolved by hot sulfuric acid. The dissolved Ti(IV) is reduced to Ti(III) by adding metallic aluminum. The reduced Ti(III) is titrated against a standard oxidizing agent, Fe(III) (ammonium iron(III) sulfate), with potassium thiocyanate as an indicator. In order to test the accuracy and applicability of the proposed method, we analysed the amounts of titanium dioxide in four types of sunscreen cosmetics, namely cream, make‐up base, foundation, and powder, after adding known amounts of titanium dioxide (1 ~ 25 w/w%). The percentages of titanium dioxide recovered in the four types of formulations were in the range between 96% and 105%. We also analysed seven commercial cosmetic products labelled with titanium dioxide as an ingredient and compared the results with those obtained from ICP‐AES (inductively coupled plasma‐atomic emission spectrometry), one of the most powerful atomic analysis techniques. The results showed that the titrated amounts were well in accord with the analyzed amounts of titanium dioxide by ICP‐AES. Although instrument‐based analytical methods, namely ICP‐MS (inductively coupled plasma–mass spectrometry) and ICP‐AES, are best for the analysis of titanium, it is difficult for small cosmetic companies to install such instruments because of their high cost. It was found that the volumetric method presented here gives quantitatively accurate and reliable results with routine lab‐ware and chemicals.     

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.     

Skin cell targeting with self‐assembled ligand addressed nanoemulsion droplets

Dermo‐pharmacy and cosmetic industries have utilized nanotechnologies for two decades. Initially proposed as vector systems for encapsulation of actives, they gained interest in increasing cutaneous bioavailability. Here, we assay the benefits of self‐assembled nanoemulsions bearing ligands for targeting specific skin cells. Nanoemulsions, small droplets ranging typically from 20 nm to 150 nm, possess key properties for further use in cosmetics: long‐term stability, optical transparency, extended range of textures and versatility. We investigated this nanoemulsion system and show ability to encapsulate a range of cosmetic actives with various physicochemical properties. Furthermore, this nanoemulsion presents a low cytotoxicity and is capable of directly targeting skin cells through simple addition of specific ligand in a one‐step production protocol. This is of interest for increasing bioavailability of actives encapsulated into nanoemulsion droplets which may have penetrated the skin barrier to specific skin cell. Taken together, these chemical and in vitro observations suggest follow‐up with in vivo models.     

Mascaras may cause irritant contact dermatitis

The majority of adverse effects of cosmetics have been attributed to soaps in Dutch and English studies, but to eye makeup in a recent Swedish study. The reactions may be caused by irritants or by sensitizing substances. The aim of the present study was to evaluate the irritation potential of commercially available mascaras. The mascaras were exposed to the skin in aluminium chambers. The skin reaction was evaluated using both visual assessments of erythema and non-invasive measurements of the skin reaction. Seven mascaras were tested on 15 healthy individuals in a randomized and blinded fashion. Two of the seven tested mascaras induced pronounced skin inflammation, when applied to normal skin under occlusion. These two mascaras were based on volatile petroleum distillate, in contrast to the other five mascaras that were conventional emulsions with stearate as the main emulsifier. The findings suggest that solvent-based mascaras might induce contact dermatitis due to its content of irritating substances.     

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.     

Dermatology and the cosmetic industry

Co-operation between the cosmetic industry and dermatology is essential for identifying potentially hazardous substances and ensuring optimal product safety. With dermatological consultation, epidemiological surveys of patients or employees in the cosmetic, toiletry or chemical industry provide useful information to distinguish product-induced or occupational dermatitis from other types of contact dermatitis or constitutional disease (such as psoriasis, lichen planus, or disorders of collagen or immune response). Some examples of the inherent complexities of this process and the solutions that have been achieved are presented. Care is necessary by dermatologists and cosmetic scientists in carrying out controlled use trials and interpreting patch test results in the search for an offending ingredient. Some medical conditions and treatment regimens of the patient/consumer that may affect the response to a cosmetic ingredient are mentioned.
La dermatologie et l'industrie cosmétique     

Novel cosmetic delivery systems: an application update

World consumers are nowadays more focused on their health and appearance. This trend is creating heightened demand for products formulated with natural and nutraceutical ingredients. Functional ingredients and innovative delivery systems are driving the new product development in the field of cosmetics. A significant number of innovative formulations are now being used in personal care with real consumer-perceivable benefits and optimized sensory attributes, resulting in an economic uplift of cosmetic industry. In fact, the U.S. market alone for novel cosmetic delivery systems has been projected to be more than $41 billion for the year 2007. Novel cosmetic delivery systems reviewed here possess enormous potential as next-generation smarter carrier systems.     

Vehicle effects on skin sensitizing potency of four chemicals: assessment using the local lymph node assay

The murine local lymph node assay (LLNA) can be used to determine the relative skin sensitizing potency of chemicals via interpolation of the quantitative dose response data generated. Using this approach we have demonstrated previously that the vehicle matrix in which a chemical allergen is encountered on the skin can have a significant influence on sensitizing potency. Estimates of relative potency are calculated from LLNA dose responses as a function of the mathematically derived EC3 value, this being the concentration estimated to induce a stimulation index (SI) of 3. To investigate further the influence of application vehicle on sensitizing potency, the LLNA has been used to examine the activity of four recognized human contact allergens: isoeugenol and cinnamic aldehyde, two fragrance chemicals; 3-dimethylaminopropylamine (a sensitizing impurity of cocamidopropyl betaine, a surfactant used in shower gel) and dibromodicyanobutane (the sensitizing component of Euxyl K 400, a preservative used in cosmetics). The four chemicals were applied in each of seven different vehicles (acetone: olive oil [4 : 1]; dimethylsulphoxide; methylethylketone; dimethyl formamide; propylene glycol; and both 50 : 50 and 90 : 10 mixtures of ethanol and water). It was found that the vehicle in which a chemical is presented to the epidermis can have a marked effect on sensitizing activity. EC3 values ranged from 0.9 to 4.9% for isoeugenol, from 0.5 to 1.7% for cinnamic aldehyde, from 1.7 to > 10% for dimethylaminopropylamine and from 0.4 to 6.4% for dibromodicyanobutane. These data confirm that the vehicle in which a chemical is encountered on the skin has an important influence on the relative skin sensitizing potency of chemicals and may have a significant impact on the acquisition of allergic contact dermatitis. The data also demonstrate the utility of the LLNA as a method for the prediction of these effects and thus for the development of more accurate risk assessments.     

Renewable sources: applications in personal care formulations

A global tendency for products considered environmentally sustainable, and ecologically obtained led the industry related to personal care formulations to fund the research and the development of personal care/cosmetics containing ingredients from natural resources. Furthermore, consumers are aware of environmental and sustainability issueans, thus not harming the environment represents a key consideration when developing a new cosmetic ingredient. In this study we review some examples of active ingredients or raw materials used in cosmetics/personal care/biomedical products that are coming from either through biotechnological systems, or as byproducts of several industries. A skin formulation containing biosynthetic actives, prepared by us and the study regarding its dermocosmetic properties are also described. The need for the standardization processes, the safety assessment tools, the improvement of the exploitation methods of these renewable sources in order the production to be ecologically and economically better are also discussed.     

Multiparticulate carriers for sun‐screening agents

Many molecular sunscreens penetrate into the skin causing photo‐allergic and photo‐toxic reactions as well as skin irritations establishing an urgent need for the development of a safer sunscreen formulation. The search for active substances, efficient combinations, and the design of novel vehicles or carriers has led to the implementation of new cosmetic systems in contrast to the classic forms such as creams or gels. Amongst various approaches utilized to improve performance of sunscreening agents, the use of multiparticulate delivery systems is gaining increasing attention amongst researchers. Multiparticulate delivery systems can be incorporated into gels, creams, liquids, powders or other formulations, and can release active agents depending on their temperature, moisture, friction, volatility of the entrapped ingredients or time. These systems also have the ability of scattering or reflecting incoming UV radiations and therefore can act as physical sunscreens on their own.     

In vitro skin permeation and retention of parabens from cosmetic formulations

Parabens are antimicrobial agents widely used in foods, cosmetics and pharmaceutical products. Although non-mutagenic, non-teratogenic and non-carcinogenic, parabens can induce allergic contact dermatitis and posses estrogenic activity. The aim of this work was to assess the skin permeation and retention of methyl- (MP), ethyl- (EP) and propyl- (PP) paraben from three commercial cosmetic creams. The results obtained indicate that parabens are capable of permeating through and accumulating in the skin. The extent of penetration depends more on paraben characteristics (solubility, lipophilicity) than on the composition of the formulation. In particular, the percentage permeated across the skin was independent of the composition of the cream used and decreased in the order MP, EP and PP, in accordance with decreasing solubility. After 8 h of contact with the skin, 60% of MP, 40% of EP and 20% of PP were found across the skin. Concerning skin retention, the percentage remaining in the skin after 8 h depends on both paraben characteristics and on the composition of the formulation used. In conclusion, it appears that only the type of paraben, in particular its water solubility, affects skin penetration whereas the composition of the emulsion, which influences skin retention, plays a secondary role. Finally, excised rabbit ear skin can be considered as a good model for human skin for in vitro experiments.