Characterization of the mechanical properties of a dermal equivalent compared with human skin in vivo by indentation and static friction tests

Background/aims: The study of changes in skin structure with age is becoming all the more important with the increase in life. The atrophy that occurs during aging is accompanied by more profound changes, with a loss of organization within the elastic collagen network and alterations in the basal elements. The aim of this study is to present a method to determine the mechanical properties of total human skin in vivo compared with dermal equivalents (DEs) using indentation and static friction tests.
Methods: A new bio-tribometer working at a low contact pressure for the characterization the mechanical properties of the skin has been developed. This device, based on indentation and static friction tests, also allows to characterize the skin in vivo and reconstructed DEs in a wide range of light contact forces, stress and strain.
Results: This original bio-tribometer shows the ability to assess the skin elasticity and friction force in a wide range of light normal load (0.5–2 g) and low contact pressure (0.5–2 kPa). The results obtained by this approach show identical values of the Young's modulus E ^* and the shear modulus G ^* of six DEs obtained from a 62-year-old subject ( E ^*=8.5±1.74 kPa and G ^*=3.3±0.46 kPa) and in vivo total skin of 20 subjects aged 55 to 70 years ( E ^*=8.3±2.1 kPa, G ^*=2.8±0.8 kpa).     

Colorimetry provides a rapid objective measurement of de novo hair growth rate in mice

Background: Depilated mice have been used as a test platform for hair growth-regulating agents. However, currently available assessment tools for hair growth in mice are less than ideal.
Methods: Tristimulus colorimetry of the fur color of depilated agouti, albino, and black mice with L ^*, a ^*, and b ^* values were performed daily until the full growth of pelage. Using light-emitting diode (LED) irradiation (650 and 890 nm) with a daily dose of 3.5 J/cm² as hair growth regulators, the hair growth rates observed by the global assessment were compared with those derived from colorimetry.
Results: In contrast to a ^* and b ^* values, L ^* values changed more drastically over time in the anagen phase regardless of fur color. Unlike the inhibitory effect of 650 nm irradiation, LED of 890 nm promoted de novo hair regrowth in mice. The difference in hair growth rates detected by colorimetry paralleled the observation made by the global assessment.
Conclusion: The L ^* value of fur color obtained by tristimulus colorimetry was a sensitive yet quantitative indicator of de novo hair growth, and could be used to project the hair growth rate in mice.     

A study of a single variant allele (rs1426654) of the pigmentation-related gene SLC24A5 in Greek subjects

Abstract:  The SLC24A5 gene, the human orthologue of the zebrafish golden gene, has been shown to play a key role in human pigmentation. In this study, we investigate the prevalence of the variant allele rs1426654 in a selected sample of Greek subjects. Allele-specific polymerase chain reaction was performed in peripheral blood samples from 158 attendants of a dermatology outpatient service. The results were correlated with pigmentary traits and MC1R genotype. The vast majority of subjects (99%) were homozygous for the Thr ¹¹¹ allele. Only two subjects from the control group (1.26%) were heterozygous for the alanine and threonine allele. Both of these Thr ¹¹¹ /Ala ¹¹¹ heterozygotes carried a single polymorphism of MC1R (one with the V92M variant and another with the V60L variant). Following reports of the rs1426654 polymorphism reaching fixation in the European population, our study of Greek subjects showed a prevalence of the Thr ¹¹¹ allele, even among subjects with darker skin pigmentation or phototype.     

Comparison of tissue viability imaging and colorimetry: skin blanching

Background: Operator-independent assessment of skin blanching is important in the development and evaluation of topically applied steroids. Spectroscopic instruments based on hand-held probes, however, include elements of operator dependence such as difference in applied pressure and probe misalignment, while laser Doppler-based methods are better suited for demonstration of skin vasodilatation than for vasoconstriction.
Objective: To demonstrate the potential of the emerging technology of Tissue Viability Imaging (TiVi) in the objective and operator-independent assessment of skin blanching.
Methods: The WheelsBridge TiVi600 Tissue Viability Imager was used for quantification of human skin blanching with the Minolta chromameter CR 200 as an independent colorimeter reference method. Desoximetasone gel 0.05% was applied topically on the volar side of the forearm under occlusion for 6 h in four healthy adults. In a separate study, the induction of blanching in the occlusion phase was mapped using a transparent occlusion cover.
Results: The relative uncertainty in the blanching estimate produced by the Tissue Viability Imager was about 5% and similar to that of the chromameter operated by a single user and taking the a ^* parameter as a measure of blanching. Estimation of skin blanching could also be performed in the presence of a transient paradoxical erythema, using the integrated TiVi software. The successive induction of skin blanching during the occlusion phase could readily be mapped by the Tissue Viability Imager.
Conclusion: TiVi seems to be suitable for operator-independent and remote mapping of human skin blanching, eliminating the main disadvantages of methods based on hand-held probes.     

Application of a pigment measuring device – Mexameter®– for the differential diagnosis of vitiligo and nevus depigmentosus

Background/purpose: Vitiligo and nevus depigmentosus (ND) present similar hypopigmented macules with significantly different prognoses. Although the distinction between the two diseases is important, differential diagnosis relies on medical history and physical examination, which is far from decisive in some cases. The Mexameter^® is an objective skin color-measuring device, and has been reported to provide a reproducible and sensitive means of quantifying small skin color differences. In this study, we investigated the usefulness of a Mexameter^® for discriminating these diseases.
Methods: A selection of 202 hypopigmented skin lesions (182 from vitiligo and 20 from ND) were the objects of this study. Using a Mexameter, MIs were obtained from lesions and symmetrically located control skin. RMIs, ratios of the MIs of lesional skins to control skins, were calculated.
Results: The mean MIs and RMIs were significantly different for vitiligo and ND. The mean RMI of ND lesions was 74±13, which was significantly higher than that of vitiligo lesions (50±24). No ND lesion had an RMI of <50%.
Conclusion: This study shows that the Mexameter^®, an objective pigment-measuring device, can be used to achieve a more accurate diagnosis of hypopigmentary disorders, and that the relative melanin index (RMI), which represents the relative pigment levels, might be a more effective parameter than the melanin index (MI) itself for comparing pigmentation differences.     

Mid-infrared spectroscopy on skin using a silver halide fibre probe in vivo

Background/aim: Mid-infrared spectroscopy is a versatile method for in vivo investigation of skin after topical treatment with skin care products.
Methods: FTIR-spectrometer (Bruker Optics) with a flexible silver halide fibre probe (Infrared Fiber Sensors).
Results: Absorbance spectra from 700 to 3000 cm⁻¹ have been recorded to gain information about proteins (amide-I and amide-II vibrations at 1650 and 1550 cm⁻¹), esters (1740 cm⁻¹), carboxylic acid (1710 cm⁻¹), polyalcohols (1050 cm⁻¹) and hydrocarbons (CH _n vibrations at 2800–3000 cm⁻¹).
Conclusions: Using the particular light guide, we were able to measure for the first time the effects of lip care products on lips directly. Furthermore, water binding and glycerol content of the skin could be determined simultaneously, as well as the replenishment of lipids by lipid-enriched bath oil.     

Skin irritation typing and grading based on laser Doppler perfusion imaging

Background/aims: Vasodilation with increased cutaneous perfusion is an essential part of an irritant inflammatory response. The aim of the present study was to investigate the usefulness of the high-resolution laser Doppler perfusion imaging (HR-LDPI) technique for investigating irritant skin reactions. Irritants may elicit clinically different reactions due to different skin penetration profiles and different modes of irritant action on the exposed tissue.
Methods: Twelve subjects were tested on the forearms using 24 h occlusive application of three concentrations of the irritants sodium lauryl sulphate (SLS) and nonanoic acid (NON) and with the topical acne drug all-trans retinoic acid (RA). Cutaneous blood flow at baseline, the increase in cutaneous blood flow and the skin area having increased perfusion were measured on day 2, day 3 and day 5.
Results: Based both on measurement of mean perfusion and area with increased perfusion, it was possible to differentiate between different clinical irritation grades on any study day. The area with increased perfusion exceeded the area with clinically visible skin reactions for irritant reactions of grade ¹/₂ and above. Irritant reactions for individual irritants could furthermore be typed using HR-LDPI. It was possible to differentiate between vehicle treatment and the different dose levels of the irritant compounds. A correlation was found between clinical scores for the individual irritants and the mean flow and the area with increased flow. The individual irritants could be differentiated due to different time courses of their skin irritation.
Conclusion: Laser Doppler imaging was found to be an important new method for characterization and grading of the inflammatory response of single exposure irritant reactions. However, standardised study procedures cannot be emphasised enough in order to obtain reliable and useful data.     

Temperature dependence of photochemical fluorescence fading in Skh-1 hairless mouse collagen

Background: Type I mammalian collagens have several photolabile fluorescent moieties that absorb UV rays capable of reaching the dermis. We studied the temperature dependence of fluorescence fading as a marker of photochemical damage.
Methods: Collagen solutions were exposed to radiation from 0 to 240 min from either a UVG-11 hand lamp, total dose=1.173 × 10³ J/m²; a UVL-21 hand lamp total dose=2.030 × 10³ J/m²; or the fluorometer, at 325±5 nm, total dose=0.156 × 10³ J/m². We recorded intensities at excitation/emission wavelengths 270/300, 270/330, 270/360, 270/400, 325/400, and 370/450 nm at T =9.0–59.3 °C.
Results: Results indicated simultaneous forward and reverse reactions. However, the 270/360 nm fluorophore could be analyzed as a second-order reaction. The Arrhenius curve showed two straight lines intersecting near the denaturation temperature, with helix activation energy E _a∼0 and coil E _a=7.6±0.6 kcal/mol (31.7±2.5 kJ/mol).
Discussion: Collagen-bound fluorophores are not just passive markers of oxidative stress and age-related damage. Their photolability to wavelengths reaching the dermis may result in pathological conditions, particularly at elevated body temperatures.     

Fucosyltransferase VII-positive, skin-homing T cells in the blood and skin lesions of atopic dermatitis patients

Abstract: Patients with atopic dermatitis (AD) have an abnormally increased frequency of cutaneous lymphocyte antigen (CLA)⁺ Th2 cells responsible for local inflammation; however, this is paradoxical, given the well-recognized defective capacity of Th2 cells to migrate to the skin sites of inflammation. These discrepant observations would stem from the ambiguity of CLA⁺ T cells, because CLA does not represent the epitope required for binding to E-selectin but the epitope generated by fucosyltransferase VII (Fuc-TVII) and because skin-homing T cells are composed of three distinct subpopulations; Fuc-TVII⁺ E-selectin ligand (ESL)⁺ CLA⁻, Fuc-TVII⁺ ESL⁺ CLA⁺ and Fuc-TVII⁻ ESL⁻ CLA⁺ cells. We therefore asked which subpopulations of skin-homing Th2 cells could be increased in the blood and skin lesions of AD. We analysed the frequencies of the three subpopulations in purified CD4⁺ peripheral blood T cells from AD patients and healthy controls by immunohistochemistry and flow cytometry. The Fuc-TVII⁺ CLA⁺ or CLA⁺ ESL⁺ CCR4⁺ cells were dramatically increased in frequency not only in the blood but also in the skin lesions of AD patients and this increase was related to the severity of the clinical symptoms. Our data indicate the clinical importance of identifying skin-homing T cells with the potent capacity to migrate into the skin by analysing their Fuc-TVII expression and E-selectin binding ability in patients with AD.     

Development of occupational skin diseases during vocational training in baker and confectioner apprentices: a follow-up study

Baker and confectioner apprentices have been included in a prospective follow-up study in the region of East Thuringia, to evaluate risk factors for the development of hand dermatitis. Starting in August 1996, the apprentices have been interviewed and examined in a standardized way right at the beginning ( n =91) of their vocational training, 6 ( n =79) and 12 months ( n =63) later. To gain objective data, TEWL score was also assessed at 3 standardized sites on the hands. In their case histories, 3.3% ( n =3) of the apprentices reported hand dermatitis. The 1st assessment after 2 to 4 weeks vocational training revealed hand eczema in 17.5% ( n =16) of the individuals. At the follow-up after 6 months of training 29.1% ( n =23), and after 12 month of training 27.0% ( n =17), of the apprentices had hand dermatitis of mild to moderate severity. Within 6 months, the TEWL score rose significantly ( p <0.001) from 11.9 g m⁻² h⁻¹ (± 5.4) to 16.8 g m⁻² h⁻¹ (± 9.5). After 12 months, the TEWL score was 14.9 g m⁻² h⁻¹ (± 4.6). For the atopic skin diathesis (> 10 points of Diepgen's atopy score), there was a significant tendency to be a predictive factor for the development of occupational hand dermatitis. TEWL score failed to correlate with the development of skin damage in our study. The same was true for respiratory atopy and metal sensitization.     

Characterization of [3H]substance P binding sites in human skin

Radioligand binding experiments were performed with crude homogenates from normal human skin in order to investigate substance P receptor density. Binding of [³H]substance P ([³H]SP) reached equilibrium after 20 min and was saturable; analysis of saturation curves gave a significantly better fit using two-site binding compared to the single-site model. Competition studies employing some selective agonists for NK1, NK2 and NK3 receptors have demonstrated that only the NK1 selective agonist, [Sar⁹, Met(O₂)¹¹]-SP, was a competitor for [³H]SP binding. In addition, the non-hydrolyzable guanosine 5'-0-(3-thiotriphosphate) altered the dissociation of SP from NK1 receptors by increasing the number of low-affinity sites. These data show that in the skin [³H]SP binds to a single population of substance P high-affinity sites, which represent NK1-type receptors.     

Prevention of psoriasis-like lesions development in fsn/fsn mice by helminth glycans

Abstract:  The helminth glycan LNFPIII is an immunomodulatory molecule, driving CD4⁺ Th2-type biasing as well as immune suppression. Psoriasis is an autoimmune disease where the immune mechanisms as well as the antigens responsible for development of immune autoreactivity are still not known. In the absence of defined immunological mechanisms, we asked whether LNFPIII would function as novel therapy for psoriasis. We tested the therapeutic efficacy of LNFPIII using the flaky skin (fsn)/fsn mutant mouse model of psoriasis-like lesion development. We found that treatment of mice with LNFPIII prevented the appearance of psoriatic skin lesions on fsn/fsn mice. Examination of the skin 2 weeks after treatment demonstrated that prevention of skin lesions was associated with maintenance of normal epidermis thickness in LNFPIII-treated mice as compared with a significantly thickened epidermis in control treated and diseased mice. In addition, cells from skin of LNFPIII-treated mice produced lower amounts of interferon-γ as compared with cells from skin of control treated diseased mice. Examination of macrophages and T cells from peripheral lymph nodes of control and LNFPIII-treated fsn/fsn mice showed that glycan treatment reduced the numbers of Gr1⁺F4/80⁺ macrophages and the numbers of CD8⁺ T cells, restoring the numbers of these two cell populations as well as the CD4 : CD8 ratio to near normal levels. Overall, the results from this study suggest that the helminth immunomodulatory glycan LNFPIII functions to prevent development of psoriatic-like skin lesions in fsn/fsn mice.     

CD28 T-cell costimulatory molecule expression in pemphigus vulgaris

Background  CD28 superfamily of immune costimulatory molecules could play an important role in autotolerance control. CD28 costimulation seems to be necessary for regulatory T cell (Treg) activation and successive suppressive activities involved in autoimmunity protection. This study investigates CD28 expression, especially inducible costimulator fraction, on T lymphocytes in pemphigus vulgaris (PV) patients.
Methods  CD28 expression on T lymphocytes was assessed in 16 PV patients during acute attack. All patients and 10 healthy control subjects were tested for lymphocyte populations, T-cell subpopulations (T-CD4⁺, T-CD8⁺), Treg and CD28 expression on T-cell subpopulations.
Results  T, B and natural killer cells average values in PV patients were close to the control group values. Compared with control group, PV values showed lower Treg (2.2% compared with 4.7%), slightly decreased CD4⁺ CD28⁺ T cells (91% compared with 95%), higher CD4⁺ CD28⁻ T cells (9% compared with 5%), decreased CD8⁺ CD28⁺ T cells (57% and 73%, respectively) and significantly enhanced CD8⁺ CD28⁻ T cells (43% compared with 27%).
Conclusions  These data suggest that Treg-mediated suppressor T-cell effects could be diminished in PV, together with an abnormal or ineffective subsequent helper T-cell suppression. CD28 high expression on helper T cells and low expression on suppressor T cells are arguments for a potential CD28 role in PV autoimmune response mechanism.

Conflicts of interest

None declared     

Graphic analysis of the relationship between skin colour change and variations in the amounts of melanin and haemoglobin

Background/aims The L*a*b* coordinate is the most commonly used colour system to measure skin colour in dermatology and cosmetology. In this system, a* and L* are often used for quantification of the degrees of erythema and pigmentation. The aim of this study was to examine whether a* and L* can be used as specific scales to indicate the amount of haemoglobin and melanin, respectively, in the skin.
Methods The a* and L* values were examined with a reflectance spectrometer in various skin conditions or lesions caused by a change in the amount of either melanin or haemoglobin, i.e. vitiligo, ultraviolet-induced pigmentation (PG), erythema resulting from slapping (ER), corticosteroid-induced blanching, erythema due to stasis by arm lowering, and a combination of PG and ER. The differences in values between the test sites and the adjacent normal skin, Δa* and ΔL*, were plotted on the Δa*–ΔL* plane and analysed statistically and geometrically.
Results L* depended substantially not only on melanin but also on haemoglobin, especially if the oxygen saturation level was expected to be low. a* was also influenced by melanin. The results of graphic analysis indicated that a linear transformation of (Δa*, ΔL*) into (ΔHb = 1.68 Δa* + 0.60 ΔL*, ΔMel =−1.06 Δa*–1.44 ΔL*) was suitable for separately estimating the change in the amount of haemoglobin (ΔHb) and in that of melanin (ΔMel).
Conclusion The results of this study may be of value for understanding the relationship between colour coordinates of the skin and the quantities of haemoglobin and melanin, and may be of use when pigmented lesions of the face are monitored by tristimulus colourimetry, as facial skin colour is affected considerably by the rich and easily variable cutaneous blood flow.     

Systematic administration of chloroquine in discoid lupus erythematosus reduces skin lesions via inhibition of angiogenesis

Background.  Discoid lupus erythematosus (DLE) is a chronic cutaneous form of lupus erythematosus, characterized by inflammation and scarring skin lesions, with lymphocyte infiltration and vasodilation. Antimalarial drugs have beneficial therapeutic effects in DLE, partially resulting from their immunomodulating and photoprotective properties. The possible influence of these drugs on angiogenesis has not been previously evaluated.
Aims.  To investigate the impact of chloroquine (CQ) treatment on the expression of vascular endothelial growth factor (VEGF, a major regulator of angiogenesis) and CD34 (a transmembrane glycoprotein expressed on endothelial cells and involved in tethering lymphocytes) in patients with DLE.
Methods.  A 3-mm skin biopsy was taken from typical skin lesions in 10 people with DLE. Another biopsy was taken from the same area after 3 months of treatment with CQ (250 mg/day). Skin sections were stained with monoclonal antibodies directed against VEGF and CD34. The intensity of epidermal VEGF expression, and the number and area of CD34-positive dermal blood vessels were assessed.
Results.  CQ treatment induced a reduction in epidermal VEGF expression. It also resulted in a significant decrease in the median number of CD34+ dermal blood vessels (from 219 to 125 vessels per mm²). Furthermore the median vessel area was significantly lowered from 9.76 × 10⁶ to 6.92 × 10⁶ mm² per mm² of the dermis.
Conclusions.  These results indicate that one beneficial effect of CQ treatment in DLE may be due to its antiangiogenic properties.     

Contribution of skin biometrology to the diagnosis of the Ehlers–Danlos syndrome in a prospective series of 41 patients

Background/purpose: The diagnosis of the Ehlers–Danlos syndrome (EDS) is primarily clinical. Clinical signs result from modifications of the rheological properties of the skin: thickness, extensibility and hydration. Our main objective was to demonstrate what skin biometry can contribute to the diagnosis and evaluation of the different types of EDS.
Methods: Forty-one patients clinically diagnosed with EDS were paired by age and sex to 41 healthy subjects with no known dermatologic disease, in particular connective tissue diseases. We measured skin thickness, extensibility, hydration and sebum secretion by skin ultrasonography, use of a Cutometer^®, a Corneometer^® and a Sebumeter^®.
Results: The skin is thinner in all three disease types (classical, hypermobility and vascular). It is more extensible only in the classical type, and more hydrated and fatty in the hypermobility type.
Conclusion: Non-invasive measurement of skin thickness and elasticity are quantitative parameters that can be used to better diagnose EDS. Moreover, the sebaceous rate can help to diagnose the hypermobility type whereas the immediate retraction distinguishes the classical form from vascular and hypermobile types.     

Mycosis fungoides skin lesions contain CD8+ tumor-infiltrating lymphocytes expressing an activated, MHC-restricted cytotoxic T-lymphocyte phenotype

In prior studies, we showed that most CD8⁺ cells infiltrating skin lesions of CD3⁺CD4⁺ mycosis fungoides were CD3⁺ T-line-age tumor-infiltrating lymphocytes (TIL) whose overall phenotype was suggestive of MHC-restricted cytotoxic T lymphocytes (CTL). However, their lack of cytotoxic-associated granzyme A mRNA suggested that they might be inactivated CTL precursors. In this study, we used single- and double-label immunohistologic techniques to assess the expression of TlA-1-reactive protein and HLA-DR by these CD8⁺TIL. Monoclonal antibody TIA-1 recognises a novel family of proteins expressed preferentially by cytotoxic cells, including some that lack grauzyme A. HLA-DR is a marker of T-cell activation. Single-label studies of 32 cases showed that CD8⁺TIL and TIA-1⁺ cells constituted a variable minority of the total cellular infiltrate and had a similar distribution. Double-label studies of 14 cases showed that in most instances the aggregate phenotype of the majority of CD8⁺TIL was CD3⁺TIA-1⁺HLA-DR⁺CD56⁻CD57⁻. These findings suggest that many of the CD8⁺TIL within skin lesions of CD3⁺CD4⁺ mycosis fungoides are activated, MHC-restricted CTL.     

Migration and penetration of a fluorescent textile dye into the skin –in vivo versus in vitro methods

Abstract:  The amount of textile dye migration from the textile and penetration into the skin is relevant when assessing the risk of textile dyes. In this paper, in vivo methods were developed using a harmless textile dye with a strong fluorescence and were then compared with in vitro methods. For the in vivo method, the textile was applied to the lower back of six volunteers wearing the textile 12 h and to the lower back of 12 volunteers during 30 min active sport. The maximum skin absorption of 55 ± 17 ng/cm² was obtained in the group engaged in sports. The in vitro methods, which involved the application of the textile to the pig ear skin, was shown to yield similar results to the 12 h in vivo group (31.2 ± 9.6 ng/cm² vs 27 ± 14 ng/cm²). The migration of the textiles into artificial sweat resulted in approximately 20  μ g/cm². The disadvantage of such textile extract applications on pig ear skin is discussed. It could be demonstrated that the absorption of the dye is strongly correlated to the amount of sweat, whereas the contact time was less important.     

Influence of age and regional differences on skin elasticity as measured by the Cutometer®

Background/aim: Aging of skin is accompanied by decrease of skin elasticity. Using the noninvasive suction device Cutometer^®, we evaluated the age and regional body differences of the viscoelastic properties of human skin. The objectives of this study were to evaluate the correlation between age and the biomechanical parameters and the regional skin variations.
Methods: A total of 96 healthy women aged 20–75 years were included in this study. The biomechanical properties of the skin were measured by using the Cutometer^®. Measurements were made on the face, upper arm and back.
Results: The age of subjects showed significant positive correlation with R4 and R6, and negative correlation with R2, R5 and R7. The face showed bigger changes of elastic properties than the arm and the back. Especially, the R7 of face was most significantly decreased with aging. We could estimate the so-called 'skin age' by using a correlation equation for this parameter.
Conclusion: The viscoelastic properties were significantly influenced by aging. Also, significant regional variations in the viscoelastic properties were observed. Skin elasticity measurement is useful for the quantitative evaluation of age-related changes.     

Skin and systemic pharmacokinetics of tacrolimus following topical application of tacrolimus ointment in adults with moderate to severe atopic dermatitis

Background  Systemic exposure to tacrolimus following topical application of tacrolimus ointment is minimal. There are, however, no data on the distribution of tacrolimus in the skin.
Objectives  To assess the distribution of tacrolimus in the skin and the systemic pharmacokinetics of tacrolimus in adults with moderate to severe atopic dermatitis after first and repeated application of tacrolimus ointment.
Methods  We investigated skin distribution of topically applied tacrolimus and systemic pharmacokinetics of percutaneously absorbed tacrolimus in adults with atopic dermatitis after topical application of tacrolimus 0·1% ointment twice daily for 2 weeks. Tacrolimus concentrations were assessed in full-thickness skin biopsies and blood samples.
Results  Of 14 patients, 11 completed treatment and were analysed. Mean ± SD tacrolimus concentrations in the skin at 24 h after first and last ointment applications were 94 ± 20 and 595 ± 98 ng cm⁻³, respectively. At 168 h after stopping treatment, values were 97% lower than at 24 h after last application. Tacrolimus concentration decreased with increasing skin depth. Systemic tacrolimus exposure after ointment application was low and highly variable, with 31% of samples below the limit of quantification (0·025 ng mL⁻¹) and 94% below 1 ng mL⁻¹. Blood concentrations at 24 h after the first and last ointment applications were 750 and 1800 times lower, respectively, than those in skin. Physicians' assessments showed that tacrolimus ointment was effective and well tolerated.
Conclusions  Tacrolimus was primarily partitioned in the skin, with minimal systemic absorption after topical application, in patients with atopic dermatitis.