The "Haptic Finger"– a new device for monitoring skin condition

Background/aims: Touching the skin is of great importance for the Clinician for assessing roughness, softness, firmness, etc. This type of clinical assessment is very subjective and therefore non-reproducible from one Clinician to another one or even from time to time for the same Clinician. In order to objectively monitor skin texture, we developed a new sensor, placed directly on the Clinician's finger, which generate some electric signal when slid over the skin surface.
Material and methods: The base of this Haptic Finger sensor is a thin stainless steel plate on which sponge rubber, PVDF foil, acetate film and gauze are layered. The signal generated by the sensor was filtered and digitally stored before processing. In a first in vitro experiment, the sensor was moved over different skin models (sponge rubber covered by silicon rubber) of varying hardness and roughness. These experiments allowed the definition of two parameters characterizing textures. The first parameter is variance of the signal processed using wavelet analysis, representing an index of roughness. The second parameter is dispersion of the power spectrum density in the frequency domain, corresponding to hardness. To validate these parameters, the Haptic Finger was used to scan skin surfaces of 30 people, 14 of whom displayed a skin disorder: xerosis ( n  = 5), atopic dermatitis ( n  = 7), and psoriasis ( n  = 2).
Results and conclusion: The results obtained by means of the sensor were compared with subjective, clinical evaluations by a Clinician who scored both roughness and hardness of the skin. Good agreement was observed between clinical assessment of the skin and the two parameters generated using the Haptic Finger. Use of this sensor could prove extremely valuable in cosmetic research where skin surface texture (in terms of tactile properties) is difficult to measure.     

Characterization of the physical properties of the stratum corneum by a new tactile sensor

Background/aims: The physical properties of the stratum corneum (SC) change with its water content, which is regulated by the presence of water solutes (natural moisturizing factors) and lipids in the SC, and are considered to be responsible for the induction of desquamation, skin surface roughness, and fine wrinkles. Recently a new type of tactile sensor developed for evaluating the physical properties of objects has been introduced as a simple, non‐invasive method to evaluate them; because the data obtained with this sensor have not yet been characterized in detail, we compared them with other physical parameters of the skin. Methods: A change in resonant frequency (Δf ) was measured under various levels of pressure applied by a tactile sensor placed on the cheeks of 29 women. We also measured high‐frequency conductance that reflects the hydration state of the skin surface, water holding capacity of the SC, transepidermal water loss (TEWL), skin flexibility, skin elasticity, amino acid composition of the SC, and desquamation index of the SC at the same time, and evaluated the correlation between Δf and other physical parameters. Results: The correlation between Δf and high‐frequency conductance of the SC, and that between Δf and the water holding capacity of the SC were substantially high. Δf under high pressure was more closely correlated with the acidic amino acid ratio of the SC. Δf also showed a correlation with desquamation index for thickness of the SC as well as with skin elasticity, independent of the applied pressure. Conclusions: Because Δf determined with the tactile sensor correlated with other physical parameters specific to the properties of the SC, such as high frequency conductance of the SC, its water holding capacity, ratio of acidic amino acids, and the desquamation index for thickness, the physical properties of the SC may be adequately evaluated with the measurements of Δf.     

In vivo skin relief measurement using a new optical profilometer

Background/aims: Usually, skin topography is quantified by means of 2D profilometry using negative- or positive-replicas. To allow a direct in vivo measurement, a new profilometer is built, based on an optical triangulation principle.
Conclusion: High speed of measurement can be reached using a non contact profilometer. The ability of a position sensing detector to read the center of gravity of the spot reflected by the skin surface, allows one to reduce the effects of the enlargement due to the skin absorption of the laser beam.     

High-frequency conductance measurement of the skin surface hydration state of dry skin using a new probe studded with needle-form electrodes (MT-8C)

Background/aims: When high-frequency conductance measurements are performed on dry scaly skin such as atopic xerosis, senile xerosis or psoriasis, the values recorded with a flat surfaced ordinary probe tend to be lower, indicating a reduced hydration state, than the actual one, because the rough and firm skin surface prevents close contact with the hard and flat surface of the applied probe.
Methods: We evaluated the usefulness of an MT-8C probe (Measurement Technologies Cincinnati, USA), whose skin-attaching portion is studded with 8 needle-like electrodes instead of a flat surfaced type, for measurments on dry skin.
Results/conclusions: The MT-8C probe yielded conductance values slightly higher than those recorded with the flat surfaced probe attached to Skicon in measuring the hydration state of moderately dry skin surface such as atopic xerosis and senile xerosis. It seems to be comparable or more sensitive than the capacitance recording with the Corneometer. The recorded values obtained with the MT-8C probe showed more variations than the latter because of its higher sensitivity and much smaller contact area, that makes it difficult to touch to the same spots repeatedly. No such a difference was observed on severely dry skin and thickly scaly psoriatic lesions.     

An in vivo study of the mechanical properties of facial skin and influence of aging using digital image speckle correlation

Background/purpose: The skin on the face is directly attached to the muscle through the superficial musculoaponeurotic system. We show that this can be used to probe skin mechanical properties, in vivo , using, digital image speckle correlation (DISC), a technique that measures the intrinsic cutaneous pore structure displacement following a natural facial deformation.
Methods: We take a series of images, which are then analyzed with DISC to create a displacement vector diagram, from which we can obtain spatially resolved information regarding facial deformation. We then studied the functional form of the displacement as a function of age, location on the face, and skin treatment. Finally, through DISC vector field analysis we investigate the mechanism of wrinkle formation.
Results: We first show that facial skin displacement follows the direction of muscular movement and reflects the magnitude of the applied forces. Using DISC vector field analysis, we find that as the skin ages the distribution of forces becomes more condensed, with a marked spatial asymmetry. Analysis of the data, in the perioral region, we find that the skin elasticity decreases exponentially with age, with a decay constant of approximately 32 years. Similar results, but with a larger amplitude, were also found for the periorbital region. Finally, DISC vector field analysis also shows that the location of maximal stress correlated with the location of existing facial wrinkles.
Conclusion: The DISC method, as a non-contact technique, is a potential clinical research tool for the diagnosis of facial skin condition and underlying muscular activity. We demonstrate how these factors can be used to monitor the effects of aging, formation of wrinkles, and the efficacy of topical applications of skin creams.     

Modern tattoos cause high concentrations of hazardous pigments in skin

Background:  Modern tattoo colourants frequently consist of azo pigments that not only contain multiple impurities but also are originally produced for car paint and the dyeing of consumer goods.
Objective:  In order to be able to assess the health risk of tattoos, it is important to determine the pigment concentration in human skin.
Methods:  We tattooed excised pigskin and human skin with a common tattoo pigment (Pigment Red 22) under various conditions. After tattooing, we quantitatively extracted the pigment in order to determine the pigment concentration in skin.
Results:  The concentration of pigments ranged from about 0.60 to 9.42 mg/cm² of tattooed skin (mean value 2.53 mg/cm²) depending upon the size of the pigment crystals, the pigment concentration applied to the skin surface, and the respective procedure of tattooing.
Conclusion:  In conclusion, high concentrations of colourants are injected into the skin during tattooing and based upon this quantification, a risk assessment of tattooing ought to be carried out.     

Mechanism of action of a lipophilic derivative of salicylic acid on normal skin

Background/aims: Keratolytics are agents used for a very long period of time to improve various skin disorders such as acne, hyperkeratoses, ichtyose etc. Very little is known about their mechanism of action on healthy skin. On man, the chronic application of a cosmetic cream containing a lipophilic derivative of Salicyclic acid (LSA) markedly improves the aspect and texture of the skin. Different methods were used to investigate the mechanisms of action of this new compound, compared to salicyclic acid.
Methods: Both non-invasive and histologic methods were used on the dorsal forearm of human volunteers treated with the products. Concerning the non-invasive methods, TEWL, silflo replica and confocal microscopy were used. On shave biopsies, various histometric parameters were measured by image analysis after different staining. The use of antibody MIB-1 reacting with the proliferating nuclear antigen Ki 67 allows one to measure the epidermis proliferation index.
Results: Compared to the excipient alone, presence of LSA 1% improves smoothness and firmness of the skin. The appearance in terms of clearness and healthy complexion is also improved. The thickening of all the living epidermis layers is obtained by both histometric measurement and confocal microscopy. This acanthosis is only recorded on the LSA-treated zones. The Ki 67 labelling study shows that LSA significantly increases the skin proliferation index.
Conclusions: Salicylic acid, and more markedly its lipophilic derivative (LSA), appear to have a significative effect on the renewal of the living epidermis. This probably explains the cosmetic improvement of the skin obtained after a 1-month treatment with a cream containing this new molecule.     

SkinChip®, a new tool for investigating the skin surface in vivo

Background/aims: Non-invasive methods used for characterizing skin micro-relief and skin surface hydration were developed in the 1980s. Although they allowed some progress in the knowledge of skin properties, they are not completely satisfactory in many aspects. Today, new technologies are emerging that may address such issues.
Methods: We adapted the technology produced by the ST Microelectronics Company for sensing fingerprint for the measurement of skin surface properties. Accordingly, we developed acquisition software for obtaining routinely the distribution of skin surface capacitance along different body sites. Image analysis softwares were also processed for collecting both the main orientations of the micro-relief lines and their density. The average value of skin capacitance is also obtained.
Results: The images allow a highly precise observation of the skin topography that can be easily quantified in terms of line density and line orientation. The mean gray levels of the images appear much closely correlated to the Corneometer values.
Conclusion: This new device appears to be a very convenient way for characterizing the properties of the skin surface. With regard to hydration, it usefully provides both the average value and the hydration chart of the investigated skin zones.     

Development of a novel method for quantitative evaluation of sensory skin irritation inhibitors

Background/aims: Sensory skin irritation is regarded as one of the most serious side effects of cosmetic use. Thus, it is desirable to develop good inhibitors of sensory skin irritation. However, it is difficult to quantify the effect of sensory skin irritation inhibitors.
Methods: We investigated the possibility of using an electrical current perception threshold (CPT) measurement for the quantitative evaluation of these inhibitors. We divided study populations into stinger and non-stinger groups based on their response to 5% lactic acid and assessed CPT values at 2000, 250, and 5 Hz on the cheek. Stingers showed significantly lower CPT values than non-stingers did at 250 and 5 Hz. We also measured CPT values before and after the application of nine materials with inhibitory effects on sensory skin irritation. To investigate the relationship between the change in CPT values and the effect of each material in the clinical stinging test, we conducted the stinging test with the test materials in a 5% lactic acid solution and with a 5% lactic acid solution (positive control).
Results: There was a positive correlation between the change in CPT values and the inhibitory effect that each material had on the stinging test.
Conclusion: The change in CPT values can be used for the quantitative evaluation of sensory skin irritation inhibitors .     

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.     

Relative contribution of intrinsic vs extrinsic factors to skin aging as determined by a validated skin age score

OBJECTIVE: To assess the relative contribution of intrinsic aging vs lifestyle factors to facial skin age. DESIGN: Prospective analysis of a cohort. SETTING: Skin research institute. STUDY SUBJECTS: A cohort of 361 white women (age range, 18-80 years) with apparently healthy skin. MEASUREMENTS: Visual and tactile assessment of facial skin features. RESULTS: Twenty-four skin characteristics were used to build a skin age score (SAS). The relationship between the SAS and chronological age followed a linear model with 2 plateaus--1 before age 30 years and 1 after age 71 years. An analysis was performed to determine whether certain lifestyle habits known to have effects on skin aging were related to the discrepancies between chronological age and the SAS. Significant effects were identified for phototype, body mass index, menopausal status, degree of lifetime sun exposure, and number of years of cigarette smoking. However, these factors accounted for only 10% of the discrepancies. Moreover, most skin characteristics used reflected changes understood to represent intrinsic aging rather than photodamage or other extrinsic factors. CONCLUSIONS: An SAS can be generated from multiple discrete signs evaluated on facial skin and is an informative tool for quantifying skin aging. The SAS is influenced by factors already recognized to affect the aging phenotypes; however, factors related to the rate of intrinsic aging, presumably genetic in character, seem to play a larger role than previously suspected.     

An evaluation of the effect of a topical product containing salicin on the visible signs of human skin aging

Background There are many different visible signs of skin aging. These include wrinkles, hyperpigmentation, lack of firmness, poor texture, enlarged pores, and dryness. While there are many topical agents that claim to deliver wide‐spectrum anti‐aging benefits, few target all of the signs of skin aging to the same extent. Salicin, an extract from white willow bark, has been researched as a potent anti‐inflammatory agent when taken orally. Based on unpublished in‐house comprehensive consumer clinical studies, it is believed salicin may have anti‐aging capabilities when applied topically to human skin. Aim This research evaluated the effect of a topical serum formulation containing salicin at 0.5% on the visible signs of skin aging. Materials and Methods This single‐center study enrolled 30 female subjects, showing mild to moderate signs of aging, between the ages of 35 and 70 having Fitzpatrick skin types ranging between I and IV. Subjects used the study serum product containing 0.5% salicin on their face twice daily for 12 weeks. Ordinal grading on a nine‐point scale (0 = none, 1–3 = mild, 4–6 = moderate, 7–9 = severe) of facial fine lines, molted pigmentation, uneven skin tone, tactile roughness, global firmness appearance, jaw‐line contour, radiance, and overall appearance was performed by investigator at baseline, week 1, week 4, week 8, and week 12. Digital photography, ultrasound, cutometry, and corneometry measurements were also performed at each time point. Results Twenty‐nine of 30 subjects successfully completed the study. No tolerability issues were reported. The clinical investigator found statistically significant improvements in wrinkles, tactile roughness, pore size, radiance, and overall appearance at week 1 time point (P ≤ 0.05) against baseline and statistically significant improvements in mottled pigmentation, global firmness, and jaw‐line contour at week 4 time point (P ≤ 0.05) against baseline. Cutometry, corneometry, and ultrasound measurements showed significant improvements at week 12 time point (P ≤ 0.05) against baseline. Conclusion Based on the findings from this study, it can be concluded that salicin has the ability to reduce the visible signs of skin aging when applied topically.     

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.     

Local tissue water assessed by measuring forearm skin dielectric constant: dependence on measurement depth, age and body mass index

Background: Tissue dielectric constant (TDC) measured at 300 MHz via the coaxial line reflection method is useful to evaluate local tissue water (LTW) and its change. Because excitation field penetration depth depends on size and geometry of the coaxial probe in contact with the skin, TDC values reflect skin and subcutaneous fat to varying depths depending on the probe used. Because tissue changes that occur with age or body mass index (BMI) may affect tissue water content and its depth distribution, our goal was to use TDC measurements to characterize depth patterns of LTW in normal tissue and to investigate the possible impact of age and BMI.
Methods: TDC was measured to depths of 0.5, 1.5, 2.5 and 5.0 mm on both forearms of 69 healthy women (age: 22–82 years, BMI: 18.7–46.1 kg/m²).
Results: Independent of age or BMI, TDC values decreased significantly with increasing measurement depth (33.7±5.8 at 0.5 mm to 21.8±3.7 at 5.0 mm) but at all depths dominant and non-dominant TDC values were similar to each other with ratios ranging from 1.025±0.081 at 0.5 mm to 1.017±0.097 at 5.0 mm. TDC values only at 2.5 and 5.0 mm decreased significantly with increasing BMI whereas TDC values only at 0.5 and 1.5 mm increased significantly with age.
Conclusion: The findings indicate that normal TDC values are affected differentially by BMI and age in a depth-dependent manner. Possible explanations are discussed.     

EEMCO guidance for the assessment of dry skin (xerosis) and ichthyosis: clinical scoring systems

Background/aims: Visual and tactile assessment of dry skin and ichthyosis is difficult and may vary. There is a need for standardized assessment according to universal scoring schemes.
Material and methods: A guidance to subjects (consumers) and experts evaluation with control of individual and other factors is presented. Scoring schemes include analogue scales, the overall dry skin score (ODS) and the specified symptom sum score (SRRC) system with grading of scaling, roughness, redness and cracks. The dry skin/ichthyosis area and severity index (DASI) is defined for dermatological evaluation of the entire skin surface. Conclusion: The EEMCO guidance is a practical research tool both for characterization of xerotic skin conditions and for efficacy substantiation of products. The guidance is developed to harmonize research in this field and improve interlaboratory comparison.     

Electrical impedance scanning: a new approach to skin cancer diagnosis

Background/aims: Skin cancer diagnosis depends, to a great extent, on visual inspection and histopathological examination of excised tissues. The aim of this study is to evaluate the ability of electrical impedance scanning to differentiate between benign and malignant skin lesions.
Methods: A preclinical study was conducted on 40 nude mice injected subcutaneously with a human melanoma strain. Impedance measurements were recorded every week to correlate electrical changes with tumor growth and histological findings. A clinical study was also performed on 178 human suspicious skin lesions before excision. The impedance measurements were correlated to the histopathological results.
Results: Normalized conductivity and capacitance, recorded on growing skin tumors in nude mice, were shown to change relative to lesion size. Necrosis, present in most of the larger lesions, was associated with a decrease in the electrical conductivity. Similar electrical parameters were used to classify human melanoma lesions with 92% sensitivity and 67% specificity. In addition, four out of five BCC lesions were correctly diagnosed. Moreover, dysplastic lesions were diagnosed with 91% sensitivity and 59% specificity. For comparison, physicians diagnosed melanoma lesions with 75% sensitivity and 87% specificity and dysplastic lesions with 46% sensitivity and 80% specificity.
Conclusions: The animal study showed that electrical impedance measurements reflect morphological changes related to the growth of a cancerous skin lesion. These findings are in agreement with a preliminary clinical study. Electrical Impedance Scanning can therefore be considered as an objective and non-invasive tool for differentiation between benign and malignant skin lesions.     

Irregularity skin index (ISI): a tool to evaluate skin surface texture

Background/aims: Irregularity of skin surface microtopography is difficult to evaluate in Euclidean geometry. Using a fast Fourier transform (FFT), it is possible to convert a space field into a frequency field and to obtain quantitative evaluation of this important feature of the skin. The aim of the present study was to test the applicability of a new parameter, derived from computer assisted FFT, to skin texture, in order to quantify its irregularity. This parameter has the additional advantage of being anisotropic.
Method: The study was conducted on 50 female volunteers. Skin replicas were performed on a healthy area that was not chronically photo-exposed. A new parameter, called "irregularity skin index" (ISI), was identified from FFT. The correlation with volunteers' age was calculated.
Results: ISI was calculated by FFT in two different directions (referred to the x and y axis of the diagram of the FFT and named, respectively, ISIωx and ISIωy). The irregularity skin indexes increased with age of the subjects, showing a correlation with age of r =0.47 (ISIωx) and r =0.51 (ISIωy).
Conclusion: By showing a relatively good correlation with age, ISI seems to be a promising parameter for the study of ageing skin.     

Split face study on the cutaneous tensile effect of 2-dimethylaminoethanol (deanol) gel

Background/aims: Beyond subjective assessments, the effect of skin tensors is difficult to assess. The present 2-phase randomized double-blind split face study was designed to compare the effect of a gel containing 3% 2-dimethylaminoethanol (deanol, DMAE) with the same formulation without DMAE.
Methods: In a first pilot study, sensorial assessments and measures of the skin distension under suction were performed in eight volunteers. In a second study conducted in 30 volunteers, shear wave propagation was measured.
Results: Large interindividual variations precluded any significant finding in the first study. The DMAE formulation showed, however, a significant effect characterized by increased shear wave velocity in the direction where the mechanical anisotropy of skin showed looseness.
Conclusion: The DMAE formulation under investigation increased skin firmness.