Skin color analysis using a spectrophotometer in Asians

Background/purpose: To objectively describe skin color, the Commission International d'Eclairage (CIE) L^*a^*b^* color coordinates and melanin and erythema indexes are used. However, it was difficult to understand the relationship among these parameters and to convert them into each other. We introduced a new technique to measure L^*a^*b^* color coordinates and the melanin and erythema indexes at the same time. We analyzed the skin color of normal Asians using this method. Methods: The skin color of the forehead, cheek, upper inner arm, dorsum of hand, and anterior chest of 148 volunteers was measured using a spectrophotometer. Using a computer analysis program, L^*a^*b^* values and the melanin and erythema indexes were presented at the same time. The averages of these data were shown according to gender, age, body parts, and correlations among the melanin and erythema indexes and L^*a^*b^* color coordinates, and then they were analyzed. Results: The averages of the melanin and erythema indexes of 148 participants were 1.10 ± 0.29 and 1.29 ± 0.38, respectively. The averages of the L^*, a^*, and b^* values were 64.15 ± 4.86, 8.96 ± 2.65, and 18.34 ± 2.39, respectively. The melanin and erythema indexes were higher in males than in females. While the correlation of the melanin index with the L^* value was negative, it was positively correlated with the a^* and b^* values. While the erythema index showed a weak correlation with the b^* value, its correlation was negative with the L^* value and positive with the a^* value. Conclusion: Our method of skin color measurement is useful. We consider the data of this study valuable basic data for the evaluation of colors of pigmental skin diseases and scars in the future.     

Skin color measurements: comparison between three instruments: the Chromameter®, the DermaSpectrometer® and the Mexameter®

Background/aims: Two types of skin reflectance instruments are available nowadays for the determination of skin color: a tristumulus colorimeter (Chromameter from Minolta) using the CIE L*a*b* color system and the narrow‐band simple reflectance meters (DermaSpectrometer from Cortex and Mexameter from Courage‐Khazaka) using the erythema/melanin indices. The purpose of this study was to compare the capabilities of the three instruments (sensitivity, repeatability and correlation) in vitro and in vivo. Methods: Comparative color measurements were carried out first in vitro on standardized color charts and subsequently in vivo on different skin areas in human volunteers. Skin color changes induced by various physico‐chemical treatments were also quantitatively evaluated with the three instruments. Results: The in vitro and in vivo repeatabilty as well as the sensitivity of the three instruments are rather good. Erythema and skin blanching could be readily quantified by the increase of the a* parameter and of the erythema indices of the simple reflectance meters. Natural UV tanning and artificial chemical tanning could be measured by the decrease of L* and increase of b* and of the melanin indices. Conclusion: The Chromameter and the two narrow‐band reflectance instruments were able to characterize skin color and to quantify small skin color changes. Moderate to high significant linear correlations could be established between the CIE L*a*b* color parameters and the erythema/melanin indices.     

The Visi-Chroma VC-100®: a new imaging colorimeter for dermatocosmetic research

Background/aims: It was the aim of this study to carry out a comparative evaluation in vitro on standardized color charts and in vivo on healthy subjects using the Visi‐Chroma VC‐100^®, a new imaging tristimulus colorimeter and the Minolta Chromameter CR‐200^® as a reference instrument. The Visi‐Chroma combines tristimulus color analysis with full color visualization of the skin area measured. The technical performances of both instruments were compared with the purpose of validating the use of this new imaging colorimeter in dermatocosmetic research. Methods: In vitro L*a*b* color parameters were taken with both instruments on standardized color charts (Macbeth and RAL charts) in order to evaluate accuracy, sensitivity range and repeatability. These measurements were completed by in vivo studies on different sites of human skin and studies of color changes induced by topical chemical agents on forearm skin. The accuracy, sensitivity range and repeatability of measurements of selected distances and surfaces in the measuring zone considered and specific color determinations of specific skin zones were also determined. Results: The technical performance of this imaging colorimeter was rather good, with low coefficients of variation for repeatability of in vitro and vivo color measurements. High positive correlations were established in vitro and in vivo over a wide range of color measurements. The imaging colorimeter was able to measure the L*a*b* color parameters of specific chosen parts of the skin area considered and to measure accurately selected distances and surfaces in the same skin site considered. Conclusion: These comparative measurements show that both instruments have very similar technical performances and that high levels of correlation were obtained in vitro and in vivo using the L*a*b* color parameters. In addition, the Visi‐Chroma presents the following improvements: 1) direct visualization and recording of the skin area considered with concomitant color measurements; 2) determination of the specific color parameters of skin areas chosen in the total measuring area; and 3) accurate determination of selected distances and surfaces in the same skin areas chosen.     

Development of a digital imaging system for objective measurement of hyperpigmented spots on the face

Background/aims: There are few available methods that can be used to quantify hyperpigmented spots on a wide area of the face. The objective of this study was to develop such a method through the use of specialized image analysis technologies. Methods: This imaging system was composed of a source of illumination whose light intensity was controlled with a dimmer, a 3-CCD video camera connected to a computer, and a positioning device used to correctly align the subject's face. This system was calibrated by adjusting the light intensity, the camera position, and white balance of the camera in order to acquire reproducible images. Using a specific algorithm for the image analysis, this system enabled us to measure both the total area of hyperpigmented spots (mm²) and the averaged skin colour tone (quasi L*a*b*) excluding the area of those hyperpigmented spots in a wide area of the face. The accuracy and reproducibility of the system was validated using a mannequin head with six standard colour chips obtained from the GretagMacbeth ColorChecker^®, and brown-coloured patches that simulated hyperpigmented spots whose colour and area were both known. The correlation between CIE L*a*b* and quasi L*a*b* values was examined by conducting simultaneous measurements of the facial skin colour of 187 subjects with a tristimulus colourimeter (Minolta Chromameter) and our imaging system. Results: The measurement errors in quasi L*a*b* values of colour chips and the area of brown patches were less than 2 and 5%, respectively, unless these chips or patches were located in the peripheral zone of the mannequin head. The variation in quasi L*a*b* values and the area of hyperpigmented spots (mm²) in five repeated measurements performed once every hour was less than 2%. There was an excellent correlation between the CIE L*a*b* and quasi L*a*b* values, and the Pearson's correlation coefficient between CIE L* and quasi L* value, for instance, was 0.908. Conclusions: As long as the region to be evaluated is limited to the cheek and periorbital areas, this system enables automatic detection of hyperpigmented spots in a wide area of the face, as well as the correct measurement of those areas and determination of skin colours.     

The effect of age on skin color and color heterogeneity in four ethnic groups

Background: Few comparative data are available on age‐related changes in skin color among different ethnic groups. The aim of the study was to measure and analyze the skin color and color heterogeneity in four different ethnic groups living in the same local environment and to determine the effects of age on these skin color characteristics. Methods: Female volunteers (385) from four ethnic populations (African‐American, Caucasian, Chinese and Mexicans) living in the same city were enrolled after informed consent. Skin color was measured on two facial areas, forehead and cheek. The subjects were further divided into six age ranges: 19–30, 31–40, 41–50, 51–60, 61–70 and 71–87 years to determine any age‐related effects on the skin color and color heterogeneity in both areas. Results: According to the L^*a^*b^* CIE system, clarity (fairness/lightness) was found to be lower in the African‐American group whereas the hue was lower in Caucasians, which means more red skin. A clear, statistically significant darkening of the skin with age was observed in all ethnic groups, while evidence of yellowing of the skin was shown in the Chinese volunteers. Overall, the skin color of the face of African‐Americans was more heterogeneous than in the other ethnic groups, but showed the least increase with age. Conclusion: Our study revealed interesting differences in skin color and color heterogeneity with respect to ethnicity and age‐related alterations. Data obtained are very useful in improving our knowledge about the skin of people of different origins and helps in the development of specific cosmetic products that are well adapted to all these populations.     

Spectrophotometric Measurement of Minimal Erythema Dose Sites after Narrowband Ultraviolet B Phototesting: Clinical Implication of Spetrophotometric Values in Phototherapy

Background

The spectrophotometer is well known to be a useful tool for estimating the objective minimal erythema dose (MED) during planning of phototherapy protocol. However, only a few spectrophotometric values are used to evaluate the erythema and pigmentation of the MED site during phototesting.

Objective

To determinea new meaning of the relationships among spectrophotometric values during phototesting.

Methods

Twenty-five patients with psoriasis and 23 patients with vitiligo were selected before undergoing narrowband ultraviolet B phototherapy. We interpreted the gross findings of erythema and measured the L^*a^*b^* values using a spectrophotometer at each phototest spot. We compared MEDs, basic spectrophotometric values (L^*a^*b^*), and b^*/L^* values separately according to skin type, and determined the correlation of each spectrophotometric value and the correlation between a^* and b^*/L^* values.

Results

Among L^*a^*b^* values, only b^* values showed a statistically significant difference between the type III and IV groups (p=0.003). There was a positive correlation only between MEDs and b^* values (p<0.05). The average b^*/L^*value in the type IV group was significantly higher than the type III group (p<0.05).

Conclusion

The higher b^* values in type IV skin indicates that skin tanning develops more prominently than type III. The correlation between MEDs and b^* values may signify that the skin pigmentation status is deepened with the higher MEDs. The difference in b^*/L^*values between type III and IV skin reflects that the b^*/L^*value is thought to be an index of tanning. The a^* value, known as an index of erythema, does not influence the degree of tanning.     

Physical measurement and evaluation of skin color changes under normal condition and post‐ultraviolet radiation: a comparison study of Chromameter CM 2500d and Maxmeter MX18

Objective: To compare the data correlation between two kinds of instruments, Chromameter CM2500d and Maxmeter MX18, in the measurement of skin color changes under normal condition and post‐ultraviolet (UV) radiation. Method: The data points of Chromameter CM2500d are based on L^*a^* values, while Maxmeter MX18 are based on M and E values, in order to compare the data correlation between these two kinds of instruments in skin color measurement on both non‐exposed and exposed sites. In addition, an evaluation of the correlation of post‐UV irradiation between these two instruments was conducted. Four different kinds of parameters post‐UV radiation were measured including minimal erythema dose (MED), immediate pigmentation dose (IPD), minimal persistent pigmentation dose (MPPD) and repeated UV radiation. The following UV radiation dosages were applied as Day 1=1.0 MED, Day 2=0.5 MED and Day 3=0.5 MED for repeated UV radiation, of which the erythema and pigmentation changes were recorded. Result: Chromameter CM2500d and Maxmeter MX18 showed good data correlation when measuring both non‐exposed and exposed sites on normal skin. L^* values were affected more easily by UV‐induced erythema than M values on skin color changes after 1 MED and repeated UV exposures. IPD, MPPD and the pigmentation data showed good correlations with the measurement of the intensive erythema formation induced by repeated UV exposures. a^* value was shown to be equally effective as E value with skin erythema measurements in response to various MEDs. However, increased erythema induced by repeated UV radiations was able to reduce the correlations between a^* and E values. On the other hand, a^* and E were shown to be equally effective in recording the erythema change courses after strong erythema responses post‐UV radiations. Conclusion: This comparative study showed that the data correlations between the two kinds of instruments were different depending on measurement conditions. Both Chromameter CM2500d and Maxmeter MX18 instrumental measurement results should be carefully evaluated by experimental conditions.     

Quantitative skin color measurements in acanthosis nigricans patients: colorimetry and diffuse reflectance spectroscopy

Tristimulus colorimetry and diffuse reflectance spectroscopy (DRS) are white‐light skin reflectance techniques used to measure the intensity of skin pigmentation. The tristimulus colorimeter is an instrument that measures a perceived color and the DRS instrument measures biological chromophores of the skin, including oxy‐ and deoxyhemoglobin, melanin and scattering. Data gathered from these tools can be used to understand morphological changes induced in skin chromophores due to conditions of the skin or their treatments. The purpose of this study was to evaluate the use of these two instruments in color measurements of acanthosis nigricans (AN) lesions. Eight patients with hyperinsulinemia and clinically diagnosable AN were seen monthly. Skin pigmentation was measured at three sites: the inner forearm, the medial aspect of the posterior neck, and anterior neck unaffected by AN. Of the three, measured tristimulus L*a*b* color parameters, the luminosity parameter L* was found to most reliably distinguish lesion from normally pigmented skin. The DRS instrument was able to characterize a lesion on the basis of the calculated melanin concentration, though melanin is a weak indicator of skin change and not a reliable measure to be used independently. Calculated oxyhemoglobin and deoxyhemoglobin concentrations were not found to be reliable indicators of AN. Tristimulus colorimetry may provide reliable methods for respectively quantifying and characterizing the objective color change in AN, while DRS may be useful in characterizing changes in skin melanin content associated with this skin condition.     

Objective measurement of periocular pigmentation

Purpose: To evaluate the Minolta CR‐400 chromameter in objectively measuring periocular/facial pigmentation in subjects of different ethnicities. Methods: The CR‐400 was used to obtain skin color measurements from 75 African‐American, Caucasian and Hispanic subjects in 16 facial and periocular locations. Comparisons between ethnic and Fitzpatrick groups and instrument reliability were analyzed. Results: Significant differences in L^* were observed among all three ethnic groups, while values a^* and b^* were less sensitive to differences in pigmentation. Comparison between Fitzpatrick groups again identified value L^* as being the most sensitive, demonstrating significant differences between the more heavily pigmented groups. The 16 facial locations measured were found to be statistically similar to each other, and the chromameter demonstrated excellent inter‐ and intra‐instrument reliability. Conclusions: The Minolta CR‐400 chromameter reliably measures facial pigmentation and can be useful for studies evaluating changes in skin pigmentation. Value L^* is the parameter that is most sensitive to differences between ethnic and Fitzpatrick groups. Overlap between groups was observed, demonstrating that in future studies, each individual must serve as their own control when monitoring changes in pigmentation. The similarity between all the locations tested demonstrates uniformity of facial pigmentation within an individual.     

The perilesional skin in vitiligo: a colorimetric in vivo study of 25 patients

Background: The aim of this work was to study in vivo the perilesional skin in vitiligo with a colorimetric method. Methods: Twenty‐five patients affected by vitiligo were included. For each patient, three different areas were considered: the lesional, the perilesional and the normal skin as far as 5 cm from the nearest vitiligo spot. Skin pigmentation measurements were performed with a chromameter. Results: The results showed that luminance L^* decreased significantly in relation to increasing distance from the vitiligo spot. As expected, L^* in the vitiligo spot was significantly higher than in the perilesional (P<0.0001) and normal skin (P<0.0001). There was a small difference in L^* between normal skin as far as 5 cm from the nearest vitiligo spot and perilesional skin. In contrast, the pigmentation index (b^*) gradually increased from lesional to perilesional to normal skin. Furthermore, the comparison of the b^* value between the normal skin as far as 5 cm from the nearest vitiligo spot was higher than perilesional skin and it was statistically significant (P<0.0001). Conclusion: Our results in vivo underline that the perilesional skin near the vitiligo spot is lighter than normal skin as far as 5 cm from the vitiligo spot.     

Preliminary studies on the relationship among peel force,quantitative measures of skin damage and subjective discomfort

Background/aims: The ability to anticipate skin damage and subject/patient discomfort due to the removal of adhesive materials without human testing is currently limited. While standardized laboratory methods have been developed, their ability to model and predict the interaction with relevant living substrate is imperfect. The aim of this study was to assess the adhesion of various materials as a function of time using the abdomen as the body site, and determine if a relationship existed with skin damage and subject discomfort. Methods: Strips of six different materials used in medical devices and known to have different adhesive properties in the laboratory setting were tested in this study. The strips were adhered to the abdomens of normal volunteer subjects for varying periods of time. Peel force was measured under conditions developed to lessen the influence of skin elasticity. Disturbance of the skin barrier was assessed by measuring transepidermal water loss; erythema by reflectance L^*a^*b^* measurements; skin cells removal by quantitation of dyed cells adhering to the test strips; and discomfort using subject self‐assessment. Results: When measured at times from 30 min to 72 h after application, the peel force was highest for materials at 30 min. The peel force for one of the six materials, designated F, was clearly higher than the others at time points from 30 min to 48 h after application. Interestingly, this material caused less disruption to the skin barrier and was reported to cause less discomfort. Conclusions: In this system, there was not a correspondence between adhesion as measured by peel force and skin damage or self‐report of discomfort. Further investigations will be required to establish the predictive value of other biophysical measurements and discomfort.     

Colorimetric measurements of iris colour and their significance in East Asian patients with skin cancer

Background. A light‐coloured iris is considered a risk factor for skin cancer in general. However, iris colour cannot be considered a plausible risk factor for skin cancer in East Asian populations because of the relative homogeneity of iris colours. Furthermore, subjective classifications of iris colour cannot distinguish between different East Asian individuals as to their likelihood of developing cancer. Aim. To measure human iris colours quantitatively and to assess the significances of iris colours with respect to skin cancer in Korean patients. Methods. Reference Commission Internationale d’Eclairage (CIE) L*a*b* coordinates on a ColorCheck chart were recorded using a reflectance spectrophotometer and compared with computed CIE L*a*b* coordinates from digital images to determine equations to calibrate CIE L*a*b* values. We then took iris images and measured iris colours and the colours of sun‐exposed and sun‐protected skin in 42 Korean patients with various cutaneous malignancies and nonmalignant dermatological diseases. Results were statistically analysed with regard to iris and skin colours in CIE L*a*b* coordinates. Results. Patients with skin cancer had significantly lighter irises or higher L* values than dermatological patients without a malignancy (P = 0.02). Colour differences (ΔE*ab) between sun‐exposed skin and sun‐protected skin were greater in men (P < 0.01) and in patients with skin cancer (P < 0.01), and the lightness (L*) values of sun‐exposed skins decreased with age (r = ?0.32, P < 0.05). Conclusions. Iris colour appears to be a possible skin cancer risk factor in East Asian populations. The larger colour differences seen between sun‐protected and sun‐exposed skin in men and in patients with skin cancer may have been due to chronic or excessive sun exposure.     

Melanin and facial skin fluorescence as markers of yellowish discoloration with aging

Background: Although one clinical sign of aging and/or photoaging is a yellowish discoloration of the facial skin, little is known about the cause of this change. In addition to the increase in the epidermal melanin content, it has been suggested that advanced glycation end products (AGEs), which are known to accumulate in photoaged skin, may affect this discoloration. Aim: The objective of this pilot study was to non‐invasively investigate the roles of melanin and AGEs in this yellowish discoloration of the facial skin. Methods: We examined the spectral reflectance at the cheek in 40 healthy Japanese women of various ages (mean age, 38.1 years) using a reflectance spectrophotometer and a spectrofluorimeter. The degree of yellowish tint was evaluated in terms of b^*. The amount of melanin in the skin was evaluated by calculating the melanin index (MI) A₆₄₀–A₆₇₀ [A_λ: log₁₀ (1/reflectance) at a wavelength of λ]. The amount of AGEs was roughly evaluated using the AGEs index, which is thought to linearly correlate with the amount of intrinsic fluorescence markers irrespective of the concentration of melanin and is defined as follows: AGEs index=I₅/SQR (I₁×I₂). In this equation, the intensities of reflectance are I₁ at an excitation wavelength of 335 nm, I₂ at an emission wavelength of 390 nm and I₅ at 390 nm under an excitation wavelength of 335 nm. Results: Both b^* and the AGEs index were significantly correlated with subject age (r=0.34, P<0.05 and r=0.68, P<0.0001, respectively). Significant correlations were also observed between MI and b^* (r=0.63, P<0.0001) and between the AGEs index and b^* (r=0.53, P<0.0005). However, no significant correlations were seen between MI and the AGEs index. Conclusion: The AGEs index does not appear to be influenced by the amount of melanin and may be utilized as an indicator of the amount of AGEs in the skin. AGEs are likely to play a role in the yellowish discoloration of skin with aging.     

Sensitivity to ultraviolet B is a risk factor for cutaneous melanoma in a Mediterranean population: results from an Italian case–control study

Background. Sun sensitivity is one of the predictors of melanoma risk, together with other individual characteristics such as skin and eye colour and number of naevi. However, it is unclear how best to measure sun sensitivity in order to quantify the individual risk of melanoma. Objectives. In this case–control study, the relationship between minimal erythema dose (MED) and skin colour (both instrumentally assessed) was investigated, and their possible role as independent risk factors for melanoma in a Mediterranean population evaluated. Methods. In total, 143 patients with cutaneous melanoma and 102 controls were enrolled in the study. Skin colour was assessed using a Minolta CR‐200 chromameter. For MED calculation, a fluorescent lamp (Philips TL 4W/12) was used as a source of ultraviolet B light. MED was defined as the lowest dose that produced an increase of 2.5 in the redness value, expressed by the parameter a* of the Commission Internationale d’Eclairage (CIE) L*a*b* colour space (Δa* = 2.5). Results. A significant excess of risk was associated with increasing L* values of skin colour (P < 0.05; OR = 1.12; 95% CI 1.01–1.24) for each unit of change. Low MED values were also associated with an increasing risk of melanoma, with an excess of risk of 18% (OR = 1.18, 95% CI 1.04–1.35) for every 10 mJ/cm² of MED reduction. Compared with the highest MED values (> 97.7 mJ/cm²), subjects with MED values ≤ €50 mJ/cm² or lower had a > 2‐fold increased risk of melanoma (OR = 2.37, 95% CI 1.05–5.38). The effect of decreasing MED value as a melanoma risk factor persisted after adjustment for skin colour and atypical naevi in a multivariate model. Conclusions. In conclusion, both instrumentally assessed skin colour and MED are significant risk factors for malignant melanoma in a Mediterranean population. MED seems be an independent variable in establishing the subject’s risk profile.     

Lack of correlation between minimal erythema dose and skin phototype in a colombian scholar population

Background: Sun exposure and skin phototype are the most relevant risk factors for skin cancer. Colombia has high levels of ultraviolet radiation during the whole year, therefore, both, high UVI's and outdoor worker's daily activities, in our country are very important risk factors for the development of cutaneous cancer. To date no study has evaluated the usefulness of Fitzpatrick's skin phototype classification in Colombians and its correlation with the minimal erythema dose (MED) and constitutional skin color. Such information is gaining importance in other nations due to the fact that several country's population is becoming more ethnically diverse. Objectives: To determine the skin phototype, accumulated sun exposure, sun protection behavior, MED and phenotype in a Colombian school population. Methods: Last year high school students from the western Antioquia were invited to participate by phone and letter through their respective school directors. A self‐questionnaire was handled to each student. A representative sample of the universe was selected for a medical examination by a dermatologist in order to validate the results of the self‐questionnaire. The constitutional skin color was determined with the chromameter CR 300 Minolta^®. The MED was defined as the minimal dose of UVB being able to induce erythema 24 h later. Results: Eight schools of the area agreed to participate in the study, and a total of 911 students (58% girls and 42% boys) filled‐out the self‐questionnaire. Sun exposure in the majority of individuals was in a level between moderate and very high. Ninety percent of students do not use any sun protection device or cream. Only a 50% of concordance between self‐assessed skin phototype vs. medical skin phototype was found, and the highest concordance corresponded to skin phototype II (82%). There was a marked difference in skin photosensitivity of Colombians compared with reports in Caucasians. We observed a marked overlapping in MED's and L^* values in phototypes II and III. Conclusions: The Fitzpatrick's classification was not useful in Hispanic populations such as ours. Therefore, a new skin‐phototype classification system is required. In our population the constitutional color was a good predictor of the MED but it did not correlate with skin phototype. The self‐assessed questionnaire method was not useful to determine skin cancer risk in our population. The majority of this population has light skin phototypes and is highly exposed to solar UV radiation without proper protection.     

Retrospective study of photodynamic therapy for pulsed dye laser-resistant port-wine stains

Pulsed dye laser-resistant port-wine stains present a therapeutic challenge. The aim of this study was to evaluate the efficacy and safety of photodynamic therapy for treating these lesions. A total of 67 patients with pulsed dye laser-resistant cervicofacial port-wine stains were retrospectively assessed after undergoing photodynamic therapy mediated with a combination of hemoporfin and 532-nm light. For objective evaluation of photodynamic therapy efficacy, first, the colorimetric changes in the port-wine stain lesions were evaluated according to the L*a*b* color coordinate system, then the values of color changes (ΔE) and blanching rate were calculated. For subjective evaluation of improvement, photographs taken before and after photodynamic therapy were evaluated by three independent assessors blindly. Patient satisfaction was also used as a factor in the subjective evaluation. Adverse events were recorded after treatment. The median ΔE decreased significantly from the pretreatment value of 13.42 to 9.90 at the 2-month follow up (P < 0.001). The median blanching rate of port-wine stains was 28.04% after an average of 1.21 sessions of photodynamic therapy. Based on the overall visual assessment, 46.2% patients showed excellent or good levels of improvement (>50% color blanching). Adverse events were minimal, transient and self-limiting. In conclusion, photodynamic therapy serves as an alternative means to treat pulsed dye laser-resistant port-wine stains.     

A quantitative assessment of the human skin surface using polarized light digital photography and its dermatologic significance

Background: Quantitative and objective investigations of parallel‐polarized light (PPL) photography for dermatologic purposes are scarce. Objective: To determine the significance of quantitative analysis of PPL photography to develop objective measurement methods of skin surface characteristics. Method: For PPL photography, a digital camera, a light‐emitting diode illuminator, and polarizing filters were arranged and kept constant. We analyzed the PPL photography images of the glabella, the medial aspect of the forearm, and the posterior aspect of the lower leg, and measured the CIELAB values. A dermatologist evaluated the clinical severity of the actual photographed sites with respect to glossiness and dryness. These clinical severities were compared statistically with the CIELAB values. Results: According to the correlation analysis, the L^* value was negatively correlated with dryness (r=?0.29869, P=0.0047) and glossiness (r=?0.35367, P=0.0185). Conclusion: The method used in this study is applicable to the quantitative evaluations of other dermatologic diseases or conditions, especially in relation to skin surface changes.     

Quantitative changes in the secretion of exosomes from keratinocytes homeostatically regulate skin pigmentation in a paracrine manner

The content and distribution of melanin in the epidermis determines the wide variety of skin colors associated with ethnic/racial diversity. Although it was previously reported that qualitative changes in keratinocyte-derived exosomes regulate melanocyte pigmentation in vitro, their practical involvement, especially in skin color development in vivo, has remained unclear. To address this unexplained scientific concern, the correlation of epidermal exosomes isolated from human skin tissues with melanosomal protein expression levels was demonstrated in this study for the first time. After confirming the quantitative effect of human keratinocyte-derived exosomes on human melanocyte activation, even in the absence of ultraviolet B (UV-B) exposure, the impact of exosomes secreted from UV-B-irradiated keratinocytes on melanogenesis was consistently detected, which suggests their constitutive role in regulating cutaneous pigmentation. Additionally, both a specific exosome secretion inducer and a suppressor were consistently found to significantly control melanin synthesis in a co-culture system composed of keratinocytes and melanocytes as well as in an ex vivo skin culture system. These results suggest that quantitative changes, in addition to already known qualitative changes, in exosomes secreted from human epidermal keratinocytes homeostatically regulate melanogenic activity in a paracrine manner, which leads to skin color determination.     

Better understanding of digital photography for skin color measurement: With a special emphasis on light characteristics

Background/Aim: Digital photography can be used to measure skin color colorimetrically when combined with proper techniques. To better understand the settings of digital photography for the evaluation and measurement of skin colors, we used a tungsten lamp with filters and the custom white balance (WB) function of a digital camera. Materials and methods: All colored squares on a color chart were photographed with each original and filtered light, analyzed into CIELAB coordinates to produce the calibration method for each given light setting, and compared statistically with reference coordinates obtained using a reflectance spectrophotometer. They were summarized as to the typical color groups, such as skin colors. We compared these results according to the fixed vs. custom WB of a digital camera. Results: The accuracy of color measurement was improved when using light with a proper color temperature conversion filter. The skin colors from color charts could be measured more accurately using a fixed WB. In vivo measurement of skin color was easy and possible with our method and settings. Conclusion: The color temperature conversion filter that produced daylight‐like light from the tungsten lamp was the best choice when combined with fixed WB for the measurement of colors and acceptable photographs.