Decreased level of ceramides in stratum corneum of atopic dermatitis: an etiologic factor in atopic dry skin?

Stratum corneum lipids are an important determinant for both water-retention function and permeability-barrier function in the stratum corneum. However, their major constituent, ceramides, have not been analyzed in detail in skin diseases such as atopic dermatitis that show defective water-retention and permeability-barrier function. In an attempt to assess the quantity of ceramides per unit mass of the stratum corneum in atopic dermatitis, stratum corneum sheet was removed from the forearm skin by stripping with cyanoacrylate resin and placed in hexane/ethanol extraction to yield stratum corneum lipids. The stratum corneum was dispersed by solubilization of cyanoacrylate resin with dimethylformamide, and after membrane filtration, the weight of the stratum corneum mass was measured. The ceramides were quantified by thin-layer chromatography and evaluated as microgram/mg stratum corneum. In the forearm skin of healthy individuals (n = 65), the total ceramide content significantly declined with increasing age. In atopic dermatitis (n = 32-35), there was a marked reduction in the amount of ceramides in the lesional forearm skin compared with those of healthy individuals of the same age. Interestingly, the non-lesional skin also exhibited a similar and significant decrease of ceramides. Among six ceramide fractions, ceramide 1 was most significantly reduced in both lesional and non-lesional skin. These findings suggest that an insufficiency of ceramides in the stratum corneum is an etiologic factor in atopic dry skin.     

Normal recovery of the stratum corneum barrier function following damage induced by tape stripping in patients with atopic dermatitis

Patients with atopic dermatitis (AD) constantly inflict mechanical damage to their skin by scratching induced by pruritus. On excoriated lesions of the cheek we found exceedingly high levels of transepidermal water loss (TEWL) as compared to those in the normal skin of healthy subjects. However, it is not clear whether the skin of patients with AD also shows an abnormally slow recovery after mechanical damage. We compared the recovery of the barrier function of the stratum corneum (SC). after its complete removal by tape stripping, in patients with AD and age-matched healthy control subjects. On the normal-looking skin of the flexor forearm, we found no difference in the recovery process of the water barrier function of the SC between the two groups. This suggests that ability to reconstruct SC barrier function after mechanical damage is not impaired in AD patients.     

Altered penetration of polyethylene glycols into uninvolved skin of atopic dermatitis patients

Involved regions of the skin in atopic dermatitis (AD) patients have an altered barrier function. Whether uninvolved skin also has a diminished barrier is controversial. To assess the barrier function of uninvolved skin in AD patients, the percutaneous penetration of polyethylene glycols (PEGs) of various molecular sizes was determined in vivo in AD patients and control subjects using tape stripping of the stratum corneum (SC). The diffusion and partition coefficients were determined using Fick's second law of diffusion. The SC thickness was similar in both groups; however, the trans-epidermal water loss was higher in atopic skin. The apparent diffusion coefficient of PEGs through atopic skin was twice as high as through normal skin, and decreased with increasing molecular weight (MW) in both groups. The partition coefficient in the skin of AD patients was half of that for normal skin but as for normal skin, there was no MW dependency. Although atopic skin exhibited altered barrier with respect to diffusion and partitioning, the permeability coefficients were nearly the same for atopic and normal skin. The results support the assumption of altered skin barrier of AD patients even in the skin that is visibly unaffected by disease.     

Olopatadine hydrochloride accelerates the recovery of skin barrier function in mice

BACKGROUND: The skin barrier function in patients with atopic dermatitis is disrupted and prolonged topical steroid therapy produces epidermal barrier disturbance. Olopatadine hydrochloride (olopatadine; Allelock; Kyowa Hakko Kogyo Co., Ltd, Shizuoka, Japan) is an antiallergic drug with histamine H(1) receptor antagonistic action. This drug alleviates skin inflammation and decreases the number of scratching episodes in a murine model of chronic contact dermatitis. OBJECTIVES: To investigate the effects of olopatadine and a steroid on the recovery of skin barrier function after barrier disruption in mice. METHODS: The skin barrier of the ears of mice was disrupted by tape stripping. The recovery of skin barrier function was monitored by measurement of transepidermal water loss (TEWL) after barrier disruption. Epidermal hyperplasia was induced by repeated tape stripping for 7 days. Olopatadine was administered orally once daily from 3 days before the first barrier disruption. Betamethasone 17-valerate (betamethasone) was applied topically once daily from 3 days before barrier disruption. RESULTS: Tape stripping led to a significant increase in TEWL. TEWL decreased with time after tape stripping and the skin barrier function recovered by over 60% within 9 h after tape stripping. The recovery of skin barrier in olopatadine-treated mice was significantly accelerated, compared with that in vehicle-treated mice. In contrast, the skin barrier recovery in mice treated with topical betamethasone was significantly delayed, compared with that in vehicle-treated mice. Combined treatment with olopatadine and betamethasone ameliorated the delay in barrier recovery induced by topical treatment with betamethasone. In addition, olopatadine significantly prevented the increase in epidermal thickness induced by prolonged barrier disruption. CONCLUSIONS: These results suggest that systemic administration of olopatadine accelerates the recovery of skin barrier function and ameliorates the adverse effects of topical steroids on skin barrier recovery.     

Impaired sphingomyelinase activity and epidermal differentiation in atopic dermatitis

A defective permeability barrier leads to the penetration of environmental allergens into the skin and initiates immunological reactions and inflammation crucially involved in the pathogenesis of atopic dermatitis (AD). Decreased stratum corneum ceramide content may cause the defect in permeability barrier function consistently found in AD. Acid and neutral sphingomyelinase (A- and N-SMase) generate ceramides with structural and signal transduction functions in epidermal proliferation and differentiation. We determined epidermal SMase activities, DNA synthesis, involucrin, loricrin, filaggrin, and keratin expression in lesional and non-lesional skin of AD patients. We found decreased epidermal A-SMase activity in lesional and non-lesional skin, correlating with reduced stratum corneum ceramide content and disturbed barrier function. N-SMase activity was reduced in non-lesional skin and more significantly reduced in lesional skin, correlating with impaired expression of cornified envelope proteins and keratins, important for skin barrier function. Changes in involucrin, loricrin, filaggrin, keratin K 5 (basal) and K 16 (proliferation associated) were noticed in non-lesional and lesional skin, whereas changes in K 10 (suprabasal), K 6 (proliferation associated), and K 17 (inflammation associated) were found only in lesional skin. In summary, reduction in SMase-generating ceramides and impaired differentiation are involved in the defective barrier function found in AD.     

Skin barrier response to occlusion of healthy and irritated skin: Differences in trans‐epidermal water loss,erythema and stratum corneum lipids

Background. Occlusion of the skin is a risk factor for development of irritant contact dermatitis. Occlusion may, however, have a positive effect on skin healing. No consensus on the effect of occlusion has been reached. Objectives. To investigate skin barrier response to occlusion on intact and damaged skin. Methods. In study A, the response to occlusion (nitrile glove material) for either 8 hr daily for 7 days or for 72 consecutive hours, respectively, was determined and compared with that of non‐occluded skin. In study B, the response to occlusion of for 72 consecutive hours of skin that had been damaged by either sodium lauryl sulfate (SLS) or tape stripping, respectively, was determined and compared with that of to non‐occluded pre‐damaged skin. Skin barrier function was assessed by measurements of trans‐epidermal water loss (TEWL) and erythema. In study A, stratum corneum lipids were analysed. Results. Occlusion of healthy skin did not significantly influence skin barrier function, ceramide profile or the ceramide/cholesterol ratio. Occlusion of the skin after SLS irritation resulted in higher TEWL than in the control (P = 0.049). Occlusion of the skin after tape stripping resulted in lower TEWL than in control skin (P = 0.007). Conclusions. A week of occlusion did not significantly affect healthy skin, but was found to decrease healing of SLS‐damaged skin, and to improve healing of tape‐stripped skin.     

Permeability barrier disruption increases the level of serine palmitoyltransferase in human epidermis

Sphingolipids play an important role in the homeostasis and barrier function of human stratum corneum. A disturbance of sphingolipid formation is supposed to be a crucial factor for the increased transepidermal water loss in common skin diseases like atopic eczema or psoriasis. The key enzyme for de novo sphingolipid synthesis is serine palmitoyltransferase, which consists of two different subunits, named LCB1 and LCB2 proteins. In order to investigate the induction of LCB2 synthesis in human epidermis, skin barrier disruption was performed by tape stripping on the forearm of healthy volunteers enough to obtain a 3-4-fold increase in transepidermal water loss. Skin punch biopsies were taken before and 0.5, 2, 4, and 8 h after tape stripping by each volunteer to measure LCB2 at the mRNA level. Additional biopsies taken before and 12 h after tape stripping were used to evaluate LCB2 at the protein level. Our results show that 0.5 and 2 h after tape stripping the LCB2 mRNA expression was decreased compared to control in all cases. A significant increase in LCB2 mRNA expression was detectable 4 h after barrier disruption, with individual variations; no further increase was detectable 8 h after tape stripping. Immunohistochemical analysis 12 h after barrier disruption showed increased LCB2 immunolocalization in the inner epidermis, whereas in the outer epidermis it was similar to control. LCB2 mRNA expression preceded the expression of the corresponding protein by 4-8 h. Our findings support the concept that an increase in transepidermal water loss is an obligatory trigger for the upregulation of serine palmitoyltransferase mRNA expression in humans.     

Role of Ceramides in Barrier Function of Healthy and Diseased Skin

Stratum corneum intercellular lipids play an important role in the regulation of skin water barrier homeostasis and water-holding capacity. Modification of intercellular lipid organization and composition may impair these properties. Patients with skin diseases such as atopic dermatitis, psoriasis, contact dermatitis, and some genetic disorders have diminished skin barrier function. Lipid composition in diseased skin is characterized by decreased levels of ceramide and altered ceramide profiles. To clarify mechanisms underlying ceramides as a causative factor of skin disease, investigators have examined the activity of enzymes in the stratum corneum on ceramide production and degradation. The activities of ceramidase, sphingomyelin deacylase, and glucosylceramide deacylase are increased in epidermal atopic dermatitis. Investigators have also compared the expression levels of sphingolipid activator protein in the epidermis of normal and diseased skin. A decreased level of prosaposin has been identified in both atopic dermatitis and psoriasis. These results indicate that decreased ceramide level is a major etiologic factor in skin diseases. Hence, topical skin lipid supplementation may provide opportunities for controlling ceramide deficiency and improving skin condition.     

Skin barrier function in patients with completely healed atopic dermatitis

Although it has been well established that the dry skin often seen in patients with atopic dermatitis shows a deranged barrier function, there is no unanimity of opinion as to whether the barrier in normal-appearing skin of patients with the disease is deranged or not. Hence, it remains unclear whether individuals with atopic dermatitis constitution have an intrinsic derangement of skin barrier function or not. To settle this problem, in the present study we examined transepidermal water loss and stratum corneum water content in normal appearing skin of the upper back of 16 patients with completely healed atopic dermatitis who had been free from skin symptoms for 5 years or more, 30 patients with active atopic dermatitis, and 39 healthy subjects. The transepidermal water loss values and the stratum corneum water content values in normal-appearing skin of the completely healed patients were not different from the values in normal controls. These findings indicate that skin barrier function is not disturbed in patients with completely healed atopic dermatitis.     

Stratum corneum and nail lipids in patients with atopic dermatitis. Decrease in ceramides--a pathogenetic factor in atopic xerosis?

Dry skin is seen in many patients with atopic dermatitis and correlates with a disturbed epidermal barrier function demonstrated by such features as increased transepidermal water loss and diminished stratum corneum hydration. With regard to the importance of stratum corneum lipids for the permeability barrier, we have analysed plantar (n = 8) and lumbar (n = 20) stratum corneum and nail lipids (n = 15) of atopic subjects by high-performance thin-layer chromatography (HPTLC). Compared with controls our investigations show a decrease in the ceramide fraction as a percentage of total lipid and a diminished ratio of ceramides and free sterols in atopic subjects. This implies that impaired ceramide synthesis may be a factor in the pathogenesis of atopic xerosis.     

High-expression of sphingomyelin deacylase is an important determinant of ceramide deficiency leading to barrier disruption in atopic dermatitis

We have previously demonstrated that there is abnormal expression of sphingomyelin (SM) deacylase-like enzyme in the epidermis of patients with atopic dermatitis (AD), which results in decreased levels of ceramides in their involved and uninvolved stratum corneum. For quantitation of the expression of SM deacylase in AD, we synthesized 16-(9-anthroyloxy) hexadecanoylsphingosylphosphorylcholine or [palmitic acid-14C] SM and used them as substrates to directly measure the activity of SM deacylase by detecting the release of labeled free fatty acid. Direct enzymatic measurements demonstrated that stratum corneum from lesional forearm skin (volar side) of AD patients has an extremely high SM deacylase activity that is at least five times higher than in the stratum corneum from healthy controls. In stratum corneum from nonlesional skin of AD patients, SM deacylase activity is still at least three times higher than in healthy controls. In contrast, stratum corneum from contact dermatitis patients shows levels of SM deacylase similar to healthy controls. In extracts of whole epidermis biopsies from AD patients, SM deacylase activities are significantly (3-fold) increased over healthy controls in the particulate fraction, whereas there is no significant difference in the activity of sphingomyelinase between AD and healthy control. In peripheral blood lymphocytes of AD patients, there is no increase in activity compared with healthy controls, indicating a possibility that the high expression of SM deacylase is highly associated with the skin of AD patients. These findings suggest that, in contrast to changes in sphingolipid metabolism due to aging, the hitherto undiscovered enzyme SM deacylase, is highly expressed in the epidermis of AD patients, and competes with sphingomyelinase or beta-glucocerebrosidase for the common substrate SM or glucosylceramide, which leads to the ceramide deficiency of the stratum corneum in AD.     

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.     

Impact of anatomical location on barrier recovery,surface pH and stratum corneum hydration after acute barrier disruption

BACKGROUND: It is not known whether distinct anatomical locations will respond with different recovery rates following acute barrier challenges. OBJECTIVES: To investigate whether barrier parameters differ at five body sites during recovery from acute disruption. METHODS: Acute barrier disruption was achieved by tape stripping and by acetone extraction of stratum corneum lipids. Transepidermal water loss (to assess barrier function), capacitance (for stratum corneum hydration) and skin surface pH were measured at each of five different body sites in 14 human volunteers. Individual measurements were obtained every 24 h for 96 h. RESULTS: Lipid-rich skin areas (e.g. the forehead) were the most vulnerable to barrier disruption by either method. While acetone treatment affected barrier function and decreased stratum corneum hydration, tape stripping similarly altered barrier function but increased capacitance values. Although the effect of barrier disruption on surface pH appeared to vary with location, no significant pattern of variation emerged. Independent of the method used for barrier disruption, the pH normalized within 96 h. CONCLUSIONS: Skin at different body sites shows distinct patterns of barrier recovery that are likely to be related to structural and physiological differences. Therefore, 'anatomically specific' regimens appear possible and relevant for the treatment of cutaneous disorders. In addition, adequate statistical analyses are essential to detect real differences in barrier recovery parameters.     

Aberrant lipid organization in stratum corneum of patients with atopic dermatitis and lamellar ichthyosis

There are several skin diseases in which the lipid composition in the intercellular matrix of the stratum corneum is different from that of healthy human skin. It has been shown that patients suffering from atopic dermatitis have a reduced ceramide content in the stratum corneum, whereas in the stratum corneum of lamellar ichthyosis patients, the amount of free fatty acids is decreased and the ceramide profile is altered. Both patient groups also show elevated levels of transepidermal water loss indicative of an impaired barrier function. As ceramides and free fatty acids are essential for a proper barrier function, we hypothesized that changes in the composition of these lipids would be reflected in the lipid organization in stratum corneum of atopic dermatitis and lamellar ichthyosis patients. We investigated the lateral lipid packing using electron diffraction and the lamellar organization using freeze fracture electron microscopy. In atopic dermatitis stratum corneum, we found that, in comparison with healthy stratum corneum, the presence of the hexagonal lattice (gel phase) is increased with respect to the orthorhombic packing (crystalline phase). In lamellar ichthyosis stratum corneum, the hexagonal packing was predominantly present, whereas the orthorhombic packing was observed only occasionally. This is in good agreement with studies on stratum corneum lipid models that show that the presence of long-chain free fatty acids is involved in the formation of the orthorhombic packing. The results of this study also suggest that the ceramide composition is important for the lateral lipid packing. Finally, using freeze fracture electron microscopy, changes in the lamellar organization in stratum corneum of both patient groups could be observed.     

Decreased levels of sphingosine,a natural antimicrobial agent,may be associated with vulnerability of the stratum corneum from patients with atopic dermatitis to colonization by Staphylococcus aureus

The stratum corneum of the skin of patients with atopic dermatitis is highly susceptible to colonization by various bacteria, including Staphylococcus aureus. The defense system of the skin against bacterial invasion appears to be significantly disrupted in atopic dermatitis skin, but little is known about the defense mechanism(s) involved. As one sphingolipid metabolite, sphingosine is known to exert a potent antimicrobial effect on S. aureus at physiologic levels, and it may play a significant role in bacterial defense mechanisms of healthy normal skin. Because of the altered ceramide metabolism in atopic dermatitis, the possible alteration of sphingosine metabolism might be associated with the acquired vulnerability to colonization by S. aureus in patients with atopic dermatitis. In this study, we measured the levels of sphingosine in the upper stratum corneum from patients with atopic dermatitis, and then compared that with the colonization levels of bacteria in the same subjects. Levels of sphingosine were significantly downregulated in uninvolved and in involved stratum corneum of patients with atopic dermatitis compared with healthy controls. This decreased level of sphingosine was relevant to the increased numbers of bacteria including S. aureus present in the upper stratum corneum from the same subjects. This suggests the possibility that the increased colonization of bacteria found in patients with atopic dermatitis may result from a deficiency of sphingosine as a natural antimicrobial agent. As for the mechanism involved in the decreased production of sphingosine in atopic dermatitis, analysis of the activities of ceramidases, major sphingosine-producing enzymes, revealed that, whereas the activity of alkaline ceramidase did not differ between patients with atopic dermatitis and healthy controls, the activity of acid ceramidase was significantly reduced in patients with atopic dermatitis and this had obvious relevance to the increased colonization of bacteria in those subjects. Further, there was a close correlation between the level of sphingosines and acid ceramidase (r = 0.65, p < 0.01) or ceramides (r = 0.70, p < 0.01) in the upper stratum corneum from the same patients with atopic dermatitis. Collectively, our results suggest the possibility that vulnerability to bacterial colonization in the skin of patients with atopic dermatitis is associated with reduced levels of a natural antimicrobial agent, sphingosine, which results from decreased levels of ceramides as a substrate and from diminished activities of its metabolic enzyme, acid ceramidase.     

上海两社区特应性皮炎患儿的皮肤屏障功能研究

【摘要】 目的 探讨上海两个社区特应性皮炎（AD）患儿及健康对照儿童皮肤屏障功能及AD皮损严重程度与皮肤屏障功能的相关性。方法 3 ~ 12岁AD患儿169例和健康对照儿童142例来自上海长宁新泾社区和嘉定菊园社区,检测前臂伸侧、屈侧及脸颊、胫前4个部位非皮损区的角质层含水量和经皮失水量（TEWL）。并用欧洲AD评分标准（SCORAD）对AD患儿临床严重程度进行评分。结果 AD患儿前臂伸侧、屈侧及脸颊、胫前四个部位的TEWL值均高于健康对照儿童（P ＜ 0.05）,角质层含水量在前臂伸侧和胫前均显著低于健康对照儿童（P ＜ 0.05）。AD患儿SCORAD与TEWL均值呈正相关,与角质层含水量均值呈负相关。结论 皮肤屏障功能可以作为评价AD临床严重程度的指标之一。     

Functional and structural changes of the epidermal barrier induced by various types of insults in hairless mice

Abstract Acute barrier disruption, regardless of the method of induction, depletes the stratum corneum intercellular lipids and this stimulates a series of lipid/ DNA synthesis activities which lead to barrier recovery. After barrier disruption by tape stripping, occlusion with a water vapor-impermeable membrane inhibits barrier repair. In this study, we investigated the changes in the murine epidermis after barrier perturbation by tape stripping and three different types of surfactants (Emalex NP-12, ENP-12; sodium dodecyl sulfate, SDS; benzalkonium chloride, BKC). To examine the effect of an artificial barrier, we covered the animals with a water vapor-impermeable membrane for 3 days following barrier disruption and then exposed them to the air for 2 days. The histological findings after occlusion or air exposure were similar. However, after air exposure for 2 days, the thickness of the epidermis including the stratum corneum and the stratum granulosum layers decreased to about half that of the epidermis after occlusion. Ultrastructural examination revealed obvious distortion of the lamellar bilayers within the stratum corneum interstices immediately after barrier disruption. After 3 days of occlusion, extensive disorganization was evident in the intercellular domain of the stratum corneum, whereas 2 days after removal of the occlusion, the normal basic unit structure of the lamellar bilayers had partially reappeared. Our findings provide evidence that the kinetic pattern of barrier repair and the morphological changes are similar after occlusion following barrier disruption regardless of the mechanism of disruption. Received: 14 August 2000 / Revised: 20 December 2000 / Accepted: 24 February 2001     

Distinct barrier integrity phenotypes in filaggrin-related atopic eczema following sequential tape stripping and lipid profiling

Background Filaggrin gene (FLG) loss‐of‐function mutations have been shown to represent the strongest so far known genetic risk factor for atopic dermatitis (AD). Whereas the barrier characteristics in FLG mutation carriers under baseline conditions have been investigated, there are only limited data on the permeability barrier function in filaggrin‐AD under compromised conditions. Aim We investigated: (i) stratum corneum (SC) integrity/cohesion; (ii) barrier recovery after controlled mechanical and irritant‐induced barrier abrogation; and (iii) the lipid composition of the non‐lesional and lesional skin of AD patients harbouring the European R501X, 2282del4, 3702delG, R2447X or S3247X FLG variants. Methods Thirty‐seven AD patients (14 FLG mutation carriers and 23 non‐carriers) and 20 healthy controls participated in the study. Stratum corneum integrity/cohesion was assessed by measurement of transepidermal water loss (TEWL) and amount of removed protein following sequential tape stripping. Barrier recovery was monitored by repeated measurements of TEWL and erythema up to 96 h after barrier abrogation. Samples for lipid analysis were obtained from non‐lesional and lesional skin using the cyanoacrylate method. Results Tape stripping revealed distinct genotype‐related impairment of the SC integrity/cohesion. No differences in the rate of barrier recovery among the groups were found. The SC lipid analysis revealed significant differences regarding the percentage amount of cholesterol, ceramide/cholesterol ratio and triglycerides in the uninvolved skin as well as the amounts of free fatty acids, CER[EOH] and triglycerides in the skin lesions of the AD FLG mutation carriers. Conclusions Our results provide evidence for discernible FLG‐related barrier integrity phenotypes in atopic eczema.     

Ceramide profiles of the uninvolved skin in atopic dermatitis and psoriasis are comparable to those of healthy skin

Ceramides are sphingolipids consisting of sphingoidbases, which are amide-linked to fatty acids. In the stratum corneum, they represent the major constituent of the free extractable intercellular lipids and play a significant role in maintaining and structuring the water permeability barrier of the skin. Using thin layer chromatography, which represents the method of the first choice in analyzing the stratum corneum ceramides, at least seven classes can be distinguished. Each ceramide class contains various species, which have the same head group and different chain lengths. As in many other skin disorders, atopic dermatitis and psoriasis show derangements in content and profile of the ceramides. Such derangements were reported for both the lesional involved as well as for the normal-appearing uninvolved skin. In this study, we focused on investigating the stratum corneum ceramides of the uninvolved skin in atopic dermatitis and psoriasis patients compared to healthy skin. The aim of the investigations was to explore possible significant and specific differences which can be accomplished for purposes of early diagnostics. The skin lipids were collected by means of an in vivo topical extraction procedure using an extraction mixture consisting of n-hexane and ethanol, (2:1). An automated multiple development-high performance thin layer chromatography (AMD-HPTLC) method with photodensitometric detection were applied to separate the ceramides and to estimate their contents. For studying their molecular profile within each ceramide class, a new method of normal phase HPLC with atmospheric pressure chemical ionization mass spectrometry were used. The results obtained by AMD-HPTLC exposed no significant alterations regarding the relative composition of the major stratum corneum lipids and primarily the ceramides. In addition, the mass spectrometric profiles within each ceramide class were similar in the patients and the healthy control subjects. In conclusion, this study revealed that the normal-appearing uninvolved skin of atopic dermatitis and psoriasis patients does not prove significant or specific deficiencies with respect to the free extractable major stratum corneum lipids and mainly the ceramides, when compared to healthy skin. Thus, they cannot be used for diagnostic purposes. Furthermore, our data are not consistent with the concept that impairments in the ceramide composition represent an obligate etiologic factor for both diseases.