Moisturizing effects of topical nicotinamide on atopic dry skin

BACKGROUND: Certain moisturizers can improve skin barrier function in atopic dermatitis. The effect of topical nicotinamide on atopic dry skin is unknown. We examined the effect of topical nicotinamide on atopic dry skin and compared the results with the effect of white petrolatum in a left-right comparison study. METHODS: Twenty-eight patients with atopic dermatitis, with symmetrical lesions of dry skin on both forearms, were enrolled, and were instructed to apply nicotinamide cream containing 2% nicotinamide on the left forearm and white petrolatum on the right forearm, twice daily over a 4- or 8-week treatment period. Transepidermal water loss and stratum corneum hydration were measured by instrumental devices. The amount of the stratum corneum exfoliated by tape stripping (desquamation index) was determined by an image analyzer. RESULTS: Nicotinamide significantly decreased transepidermal water loss, but white petrolatum did not show any significant effect. Both nicotinamide and white petrolatum increased stratum corneum hydration, but nicotinamide was significantly more effective than white petrolatum. The desquamation index was positively correlated with stratum corneum hydration at baseline and gradually increased in the nicotinamide group, but not in the white petrolatum group. CONCLUSIONS: Nicotinamide cream is a more effective moisturizer than white petrolatum on atopic dry skin, and may be used as a treatment adjunct in atopic dermatitis.     

Facilitating facial retinization through barrier improvement

The utility of topical tretinoin as a treatment for improving the appearance of photodamaged skin is limited by irritation that occurs during the early phases of facial retinization. The observed side effects are consistent with stratum corneum barrier compromise. This paired double-blinded study was conducted to determine if preconditioning the skin with a barrier-enhancing cosmetic facial moisturizer before beginning tretinoin therapy and continuing moisturizer application during therapy would mitigate these side effects. Women with facial photodamage were recruited and randomly assigned to apply one cosmetic moisturizer to one side of the face and the other cosmetic moisturizer to the other side of the face twice daily for 10 weeks. One moisturizer contained a mixture of vitamins (niacinamide, panthenol, and tocopheryl acetate) to enhance stratum corneum barrier function, and the other moisturizer contained similar moisturizing ingredients but no vitamins. Daily full-face treatment with tretinoin cream 0.025% commenced 2 weeks into the study. Subjects' facial skin condition was monitored via investigator assessments, instrumental measurements, and subject self-assessments. The results show that improving stratum corneum barrier function before beginning topical tretinoin therapy and continuing use of a barrier-enhancing cosmetic moisturizer during therapy facilitates the early phase of facial retinization and augments the treatment response.     

Acute irritant threshold correlates with barrier function,skin hydration and contact hypersensitivity in atopic dermatitis and rosacea

The aim of the study was to disclose interactions between epidermal barrier, skin irritation and sensitization in healthy and diseased skin. Transepidermal water loss (TEWL) and stratum corneum hydration (SCH) were assessed in adult patients with atopic dermatitis (AD), rosacea and healthy controls. A 4‐h patch test with seven concentrations of sodium lauryl sulphate was performed to determine the irritant threshold (IT). Contact sensitization pattern was revealed by patch testing with European baseline series. Subjects with a lower IT had higher TEWL values and lower SCH. Subjects with positive allergic reactions had significantly lower IT. In AD, epidermal barrier deterioration was detected on both volar forearm and nasolabial fold, while in rosacea, impeded skin physiology parameters were observed on the facial skin only, suggesting that barrier impediment is restricted to the face in rosacea, in contrast with AD where the abnormal skin physiology is generalized.     

Measuring the effects of topical moisturizers on changes in stratum corneum thickness, water gradients and hydration in vivo

Background Moisturizers are the most commonly used topically applied product for the treatment of dry skin conditions. They affect many properties and functions of the stratum corneum but some moisturizers have been reported to be detrimental to barrier function. Stratum corneum barrier function is a composite of its total structure and thickness but few studies have taken this into account. As a biosensor, the stratum corneum (SC) will change its structure in response to treatment and a swelling effect has been clearly demonstrated by skin hydration. Recently several moisturizing agents have been shown to have an effect on SC swelling behaviour with conflicting results. However, there is a paucity of data reported for measuring the effects of long‐term usage of moisturizers on SC thickness in vivo as, until recently, traditional techniques did not have the resolution to measure the effects of moisturizers on nonpalmoplantar body sites. The development of confocal Raman spectroscopy for use in human subjects provides noninvasive, real‐time, in vivo measurement of SC water concentration profiles and we have also used this state of the art equipment to measure the effect of the long‐term use of moisturizers on SC thickness for the first time. Objectives To validate the use of confocal Raman spectroscopy (CRS) to measure SC thickness and then use it to investigate the short‐ and long‐term effects of moisturizers (one of which is known to improve SC barrier function) on SC thickness, water gradients and hydration. Methods Two studies were conducted: (i) to validate the use of CRS for measuring SC thickness through comparison with optical coherence tomography (OCT); and (ii) once validated to use CRS to measure the long‐term effects of three commercially available moisturizers (A, B, C) on SC thickness and water gradients, together with total hydration, over a 3‐week period (2 weeks of treatment and 1 week regression) and compare the spectroscopy‐derived hydration value with instrumentally derived capacitance hydration values. Results (i) A strong, positive correlation in SC thickness was obtained between CRS and OCT (OCT‐derived thickness = 0·96 × CRS‐derived thickness, r² = 0·93; P <0·0001). OCT was shown, however, to have a lower resolution than CRS in distinguishing SC thickness on thinner nonpalmoplantar body sites. Using the CRS method, differences in SC thickness were readily apparent on different body sites (cheek 12·8 ± 0·9 μm, volar forearm 18·0 ± 3·9 μm, leg 22·0 ± 6·9 μm). (ii) Examining the effects of moisturizers in a blinded, randomized 3‐week study in human volunteers (n = 14) demonstrated that only one commercially available formulation (A) changed SC water gradients, thickness and hydration as measured by CRS. These hydration data did not directly correlate with capacitance hydration values. Conclusions (i) In vivo CRS was validated as a technique to measure SC thickness on both palmoplantar and, particularly, on nonpalmoplantar skin sites. (ii) Moisturizers improve skin moisturization but in this study only formulation A improved SC thickness, water gradients and hydration as measured by CRS. We hypothesize that this was due to compositional differences between the products. We believe that niacinamide (nicotinamide, vitamin B₃) is probably contributing significantly to this effect, as it has been proven to increase epidermal lipogenesis and SC barrier function in other studies. These results show that by using CRS, we were able for the first time to determine the effect of moisturizer on multiple SC barrier endpoints including SC thickness, and water content as a function of depth and total SC water content.     

Gentle Cleansing and Moisturizing for Patients with Atopic Dermatitis and Sensitive Skin

Atopic dermatitis is a common condition characterized by pruritus, inflammation, and dryness of the skin. Inflammation disrupts the barrier function of the stratum corneum, predisposing the skin to be dry, and increases susceptibility to irritants and secondary bacterial infection. Sensitive skin is common, reported by 40–50% of women and 30% of men in the US, Europe, and Japan. Basic requirements in managing eczema and sensitive skin include effective cleansers that do not compromise skin barrier integrity, alleviation of skin dryness, and restoration of skin barrier function through the use of therapeutic moisturizers. The selection of a skin cleanser is therefore an important part of managing these conditions. Studies have reported clinical improvement with the use of soap-free cleansers in combination with topical treatments. While topical corticosteroids and immunosuppressive agents are mainstays of treatment for atopic dermatitis, therapeutic moisturizers are important adjuncts. Moisturizers improve skin hydration, reduce susceptibility to irritation, restore the integrity of the stratum corneum, and enhance the efficacy of topical corticosteroids.     

Effect of long-term use of moisturizer on skin hydration, barrier function and susceptibility to irritants

Moisturizers are often used in the prevention and treatment of irritant contact dermatitis. The present study was to determine whether long-term daily use of a moisturizer on normal skin would affect skin barrier function, hydration state, or susceptibility to sodium lauryl sulphate. Healthy volunteers used a moisturizer on one forearm 3 times daily for 4 weeks. The other forearm served as a control. Afterwards both forearms were challenged with a patch-test of sodium lauryl sulphate. Skin barrier function was evaluated by measuring trans-epidermal water loss and skin hydration by measuring electrical capacitance. Electrical capacitance was significantly increased on the treated arm during the treatment period. After challenge with sodium lauryl sulphate, transepidermal water loss was significantly higher on the arm treated with moisturizer than on the control arm. The results suggest that long-term treatment with moisturizers on normal skin may increase skin susceptibility to irritants.     

【开放获取】皮肤干燥是通透屏障功能受损的表现吗？

【摘要】 有学者认为,皮肤干燥是表皮通透屏障功能受损的表现,但目前尚没有足够的证据证明这一观点。实际上,皮肤干燥是角质层含水量降低的表现。角质层含水量主要由角质层天然保湿因子的量决定,而表皮通透屏障功能则主要由角质层脂质的质和量以及结构蛋白决定。如果皮肤干燥是由表皮通透屏障功能降低所致,那么,角质层含水量应当与透皮失水率呈负相关性。但是研究表明,无论是正常人皮肤、鱼鳞病皮损或皮脂腺缺乏的小鼠皮肤,角质层含水量与透皮失水率均无负相关性。相反,有研究显示,人角质层含水量与透皮失水率呈正相关性。因此,皮肤干燥似乎不是表皮通透屏障功能受损的表现。     

Do moisturizers work?

Moisturizers are used on large body surfaces to maintain the smoothness of the skin and to break the dry-skin cycle. Many healthcare professionals and patients overlook the importance of moisturizers and do not consider them to be 'active' treatments. However, evidence from clinical and experimental studies shows that moisturizers enhance both the smoothness and hydration of skin. Different moisturizers have different ingredients, and each may have a different mode of action. Some smooth the skin, others affect barrier function. Some enhance barrier function in both diseased and normal skin. Others impair barrier function in both diseased and normal skin. Defective barrier function may trigger the development of eczema. The composition of a particular moisturizer should reflect its desired therapeutic effect, i.e. a moisturizer to diminish dryness may need different ingredients from those required to improve barrier function. The content of excipients, such as emulsifiers, chelating agents and antioxidants, may have greater impact than is commonly believed. Greater tailoring of moisturizers will improve their efficacy. Confidence in the therapeutic effects of moisturizers will be enhanced by well-designed randomized controlled trials.     

Hydrophilic and lipophilic moisturizers have similar penetration profiles but different effects on SC water distribution in vivo

Abstract:  Dry skin is often treated with hydrophilic and/or lipophilic moisturizers. Hydrophilic moisturizers must penetrate the stratum corneum (SC) deeply to function properly, whereas lipophilic moisturizers should remain in the upper SC layers. In this study, both types of moisturizers were applied on volunteers for 3 h, after which the relative amount of moisturizer and the water distribution in the SC were determined using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy in combination with tape-stripping. The results show that while hydrophilic moisturizers penetrate much more readily than lipophilic moisturizers, the latter are abundantly present in the upper regions of the SC. It was also observed that a 3-h treatment with lipophilic moisturizer did not result in increased water levels in the SC, whereas hydrophilic moisturizers retained water where they are located. The results suggest that upon prolonged application, adequate amounts of moisturizer can be obtained in those regions where they may cause moisturization in the central part of the SC. However, a single application of 3 h is probably too short to exert increased hydration as measured with ATR-FTIR.     

Effect of different moisturizers on SLS-irritated human skin

Moisturizers are widely used to treat irritant contact dermatitis (ICD). Their use is, however, not well-documented and standardized models for testing skin care products are needed to acquire documentation of their efficacy. The present study was undertaken to evaluate the effect of 6 commonly-used moisturizers on the recovery of irritated human skin. No commercial interests were involved in the study. 36 healthy volunteers had patch tests with SLS 0.5% applied on their forearms/upper arms for 24 h. After irritation of the skin, all volunteers had a moisturizer applied on one forearm/upper arm, respectively, 3 x daily for the following 5 days. The other forearm/upper arm served as an untreated control. Each moisturizer was tested on 12 volunteers and each volunteer tested 2 moisturizers at the same time. Evaluation was done on days 1, 3 and 8 by transepidermal water loss, electrical capacitance, laser Doppler flowmetry, DermaSpectrometry and clinical scoring. All 6 moisturizers were found to accelerate regeneration of the skin barrier function when compared to irritated non-treated skin. The most lipid-rich moisturizers improved barrier restoration more rapidly than the less lipid-rich moisturizers. We suggest this experimental model for further moisturizer efficacy testing.     

Effect of moisturizers on epidermal barrier function

A daily moisturizing routine is a vital part of the management of patients with atopic dermatitis and other dry skin conditions. The composition of the moisturizer determines whether the treatment strengthens or deteriorates the skin barrier function, which may have consequences for the outcome of the dermatitis. One might expect that a patient's impaired skin barrier function should improve in association with a reduction in the clinical signs of dryness. Despite visible relief of the dryness symptoms, however, the abnormal transepidermal water loss has been reported to remain high, or even to increase under certain regimens, whereas other moisturizers improve skin barrier function. Differing outcomes have also been reported in healthy skin: some moisturizers produce deterioration in skin barrier function and others improve the skin. Possible targets for barrier-influencing moisturizing creams include the intercellular lipid bilayers, where the fraction of lipids forming a fluid phase might be changed due to compositional or organizational changes. Other targets are the projected size of the corneocytes or the thickness of the stratum corneum. Moisturizers with barrier-improving properties may delay relapse of dermatitis in patients with atopic dermatitis. In a worst-case scenario, treatment with moisturizing creams could increase the risks of dermatitis and asthma.     

Noninvasive biophysical assessments of the efficacy of a moisturizing cosmetic cream base for patients with atopic dermatitis during different seasons

BACKGROUND: The use of emollients is recommended for patients with atopic dermatitis (AD) to maintain improved condition. OBJECTIVES: To ascertain objectively the effectiveness of a moisturizing cream for patients with AD during different seasons. METHODS: We conducted clinical evaluations, noninvasive biophysical measurements and biochemical analyses of the stratum corneum (SC) components of the volar forearm skin of 23 patients with AD after a moisturizer was applied twice daily for 4 weeks. The moisturizer was formulated according to the consensus of cosmetic scientists belonging to major Japanese cosmetic companies. The nontreated forearm served as a control. RESULTS: After using the moisturizer treatment, the hydration of the SC significantly increased together with a decrease in the desquamation measurements and an improvement in the regularity of skin surface corneocytes. An improvement was observed in the SC barrier function in winter, but was achieved only after 4 weeks in late spring during which time there even occurred exacerbation of skin conditions in three patients. With use of the moisturizer treatment, we found no change in the SC content of free amino acids or ceramides, the ratio of interleukin (IL)-1 receptor antagonist to IL-1alpha, the ratio of immature to mature cornified envelopes, the size of the corneocytes or the emergence of parakeratotic cells in the skin surface corneocytes. CONCLUSION: Treatment with an adequate moisturizer is beneficial for the dry skin of patients with AD during the dry, cold season but it does not influence the impaired SC barrier function as effectively in the less arid season.     

The 24‐hr, 28‐day,and 7‐day post‐moisturizing efficacy of ceramides 1, 3, 6‐II containing moisturizing cream compared with hydrophilic cream on skin dryness and barrier disruption in senile xerosis treatment

Direct replacement of decreased ceramides in the stratum corneum can be efficacious for skin hydration, skin barrier function, and skin pH. Our study aimed to evaluate the 24‐hr, 28‐day, and 7‐day post‐moisturizing efficacy of ceramide‐containing moisturizer in senile xerosis treatment. A split site, double‐blinded, randomized, controlled study was conducted in 24 senile subjects (91.7% females, mean age 54.83 ± 5.45 years) with mild to moderate xerosis, who were randomized to receive ceramide‐containing moisturizer or hydrophilic cream, daily applied on each side of the shin. A single application of ceramide‐containing moisturizer increased skin hydration, while improving transepidermal water loss (TEWL) and skin pH for up to 24 hr, with statistically significant difference. After 28 days of twice‐daily application, more significant improvement on skin hydration, barrier function, and skin pH was observed in those with ceramide‐containing moisturizer at all‐time points. At day 28, there was a statistically significant decrease of hemoglobin index, wrinkle, and texture on the ceramide treated side. The 7‐day post‐moisturizing efficacy on the ceramide treated side was superior for skin hydration, TEWL, skin pH, and wrinkle. Thus, the ceramide‐containing moisturizer can be a novel promising treatment for senile xerosis.     

Effect of moisturizers on skin susceptibility to irritants

Moisturizers are used for the treatment of dry and irritated skin. The benefit of moisturizers when used on normal skin has recently been challenged, since an earlier study indicated that the increased hydration that follows long-term use of moisturizers on normal skin may facilitate penetration of irritants. The aim of the present study was to evaluate short-term use of 2 different moisturizers used on normal skin: cream A (high lipid content) and B (moderate/low lipid content). Nineteen healthy volunteers applied the moisturizers on the upper arm/forearm 3 times daily for 5 days, while the other upper arm/forearm served as symmetrical control. The day after moisturizer treatment was stopped the skin was challenged with a patch test of sodium lauryl sulphate. Skin reactions were evaluated by bioengineering measuring methods and clinical scoring. Skin response to sodium lauryl sulphate was increased on moisturizer-treated arms compared to controls for one of the moisturizer (cream A), while this was not statistically significant for the other moisturizer (cream B). Data confirm previous indications that some moisturizers when used on normal skin may increase skin susceptibility to irritants.     

Functional analysis of the stratum corneum of scalp skin: studies in patients with alopecia areata and androgenetic alopecia

Abstract Because of the presence of thick long hairs on the scalp, little information is available concerning the functional characteristics of the stratum corneum (SC) of scalp skin. We therefore conducted a functional study of the SC of lesional scalp skin of patients with alopecia areata and of patients with androgenetic alopecia. We compared the scalp with the cheek and the flexor surface of the forearm (volar forearm). The water barrier function of the scalp SC of both patient groups, in terms of transepidermal water loss (TEWL), was almost comparable to that of the volar forearm, and was far better than that of facial skin. However, hydration of the scalp skin surface, as evaluated by measurement of high-frequency conductance, was markedly higher than that of facial skin, and showed significantly higher values than the volar forearm. These characteristics seem to be dependent, at least to some extent, on the amount of sebum-derived skin surface lipids because these were abundant on the scalp skin. Moreover, removal of skin surface lipids led to a significant decrease in skin surface hydration. The superficial corneocytes, the size of which reflects the proliferative activity of the epidermis, were substantially smaller on the scalp than on the volar forearm but significantly larger than on the cheek. These findings suggest that the rate of turnover of the scalp epidermis is intermediate between that of the facial and volar forearm epidermis. We conclude that the SC of the scalp skin in humans is functionally distinct from that of the face and extremities. Received: 6 January 2000 / Revised: 11 August 2000 / Accepted: 25 September 2000     

Biophysical assessment of atopic dermatitis skin and effects of a moisturizer

BACKGROUND: The mechanisms of the skin barrier impairment in patients with atopic dermatitis (AD) are still unknown and need further studying. OBJECTIVE: We evaluated the skin of healthy subjects and of patients having atopic dermatitis with an instrument measuring electrical impedance and other noninvasive methods (transepidermal water loss, capacitance) and studied the effects of a new emollient [Proderm (Pro-Q in the USA)]. METHODS: After a 2-week washout period, we treated clinically noneczematous skin on the forearm of 24 patients with AD and assessed the effects with the noninvasive methods. 22 healthy subjects were used as controls. RESULTS: The findings indicate that barrier function and hydration, and certain patterns of electrical impedance of AD skin are abnormal compared with normal skin. Moreover, there was an increase in hydration in patients' skin after treatment and a reversal of certain impedance indices towards normal. CONCLUSIONS: Our findings demonstrate that the moisturizer we used changes some biophysical parameters when applied to atopic skin. In addition, a technique based on electrical impedance seems to give valuable information in atopic skin studies, especially the effects of moisturizers.     

Electrical measurement of moisturizing effect on skin hydration and barrier function in psoriasis patients

Transepidermal water loss (TEWL) in psoriatic skin lesions seems to be related to the severity of the psoriasis, and the electrical capacitance and conductance of the skin are indicators of the hydration level of the stratum corneum. We compared the characteristics of these electrical measurements, in assessing the persistent effect of a moisturizing cream on skin hydration and barrier function in psoriasis patients. Seventeen Korean psoriasis patients were recruited. Their right leg was treated with the moisturizer twice daily for 6 weeks, while their left leg was used as the control site. For each patient, one psoriatic plaque on each leg was selected as the involved psoriatic lesion. Uninvolved psoriatic skin was regarded as the apparently healthy looking skin 4-5 cm away from the periphery of the psoriatic lesion. The TEWL, electrical capacitance and conductance were measured, in order to evaluate the barrier function and hydration level of the stratum corneum. The clinical and biophysical data for each patient were recorded at the start of the study and after 2, 4 and 6 weeks. The degree of skin dryness at the applied area improved progressively. The electrical capacitance at the treated psoriatic lesion increased significantly after 2 weeks, and this improvement was maintained during the entire study period. However, no noticeable change was observed in the electrical conductance. The TEWL showed an inverse pattern to that of the skin capacitance, decreasing during the study period. The skin capacitance and TEWL exhibited good correlation with the visual assessment of skin dryness, but the skin conductance did not. Our data suggest that electrical capacitance and TEWL may be useful in the evaluation of the effect of a moisturizer on the hydration status and barrier function of psoriatic skin.     

含透明质酸及白藜芦醇成分护肤品对干性皮肤屏障功能的影响

目的研究含有透明质酸和白藜芦醇的安特柔产品对于干性皮肤屏障功能的影响及保湿效果。方法入选皮肤中度干燥的女性受试者32例,采用自身左右对照的方法,比较安特柔沐浴洗发露与普通洁肤香皂清洁后皮肤屏障功能的差别,遂后使用安特柔保湿霜,观察6 h后及连续试用产品1周后皮肤屏障功能指标的变化。结果相比普通洁肤香皂清洁,安特柔产品清洁后皮肤经皮水分丢失(TEWL)不但没有升高反而下降(P0.05),pH值升高程度低于普通洁肤香皂(P0.05),角质层含水量轻微增加但差异无统计学意义(P=0.480);安特柔保湿霜单次使用后6 h,身体左右两侧皮肤角质层含水量均明显提高、TEWL下降,与基线相比P0.05,皮肤p H值均恢复到基线水平(P=0.094)。连续使用安特柔沐浴洗发露和保湿霜1周后,角质层含水量较基线进一步增加,较单次使用后6 h也有轻度的增加(P0.05);TEWL继续下降,p H值继续维持在偏酸范围内。连续使用1周后干性皮肤者皮肤的光滑度、干燥度和脱屑等均有显著改善;受试者自我评价50%的人认为皮肤的光滑度、干燥度、瘙痒和鳞屑有中度以上改善。结论安特柔系列产品具有很好的保湿效果和帮助屏障功能恢复的作用,单次使用后6 h仍有效,长期使用能很好地改善皮肤干燥。     

麻风患者愈后表皮某些生理功能障碍研究

目的：了解麻风愈后者其原受累及部位是否存在角质层生理功能障碍。方法：利用多功能皮肤生理仪对麻风患者痊愈后前臂原皮损处角质层含水量、酸碱度、透过皮肤水分丢失率及屏障功能的恢复速度进行测量。结果：与正常对照组相比，麻风愈后者原皮损处角质层含水量明显降低（P〈0．002），以瘤型麻风患者降低幅度最大；皮肤表面的pH明显增高（P〈0．0001），界线类偏结核型患者pH改变不甚明显；麻风愈后者原皮损处的基础表皮通透屏障功能好于正常人，以界线类偏瘤型患者水分丢失量降低最明显：麻风愈后者原皮损处表皮通透屏障功能的恢复速度无明显改变。结论：麻风患者痊愈后仍然有角质层生理功能障碍。     

Role of Topical Emollients and Moisturizers in the Treatment of Dry Skin Barrier Disorders

Emollients and moisturizing creams are used to break the dry skin cycle and to maintain the smoothness of the skin. The term 'moisturizer' is often used synonymously with emollient, but moisturizers often contain humectants in order to hydrate the stratum corneum. Dryness is frequently linked to an impaired barrier function observed, for example, in atopic skin, psoriasis, ichthyosis, and contact dermatitis. Dryness and skin barrier disorders are not a single entity, but are characterized by differences in chemistry and morphology in the epidermis. Large differences also exist between moisturizing creams. Moisturizers have multiple functions apart from moistening the skin. Similar to other actives, the efficacy is likely to depend on the dosage, where compliance is a great challenge faced in the management of skin diseases. Strong odor from ingredients and greasy compositions may be disagreeable to the patients. Furthermore, low pH and sensory reactions, from lactic acid and urea for example, may reduce patient acceptance. Once applied to the skin, the ingredients can stay on the surface, be absorbed into the skin, be metabolized, or disappear from the surface by evaporation, sloughing off, or by contact with other materials. In addition to substances considered as actives, e.g. fats and humectants, moisturizers contain substances conventionally considered as excipients (e.g. emulsifiers, antioxidants, preservatives). Recent findings indicate that actives and excipients may have more pronounced effects in the skin than previously considered. Some formulations may deteriorate the skin condition, whereas others improve the clinical appearance and skin barrier function. For example, emulsifiers may weaken the barrier. On the other hand, petrolatum has an immediate barrier-repairing effect in delipidized stratum corneum. Moreover, one ceramide-dominant lipid mixture improved atopic dermatitis and decreased transepidermal water loss (TEWL) in an open-label study in children. In double-blind studies moisturizers with urea have been shown to reduce TEWL in atopic and ichthyotic patients. Urea also makes normal and atopic skin less susceptible against irritation to sodium laurilsulfate. Treatments improving the barrier function may reduce the likelihood of further aggravation of the disease. In order to have optimum effect it is conceivable that moisturizers should be tailored with respect to the epidermal abnormality. New biochemical approaches and non-invasive instruments will increase our understanding of skin barrier disorders and facilitate optimum treatments. The chemistry and function of dry skin and moisturizers is a challenging subject for the practicing dermatologist, as well as for the chemist developing these agents in the pharmaceutical/cosmetic industry.