Hirotsugu Takiwaki

Guidelines for measurement skin colour and erythema A report from the Standardization Group of the European Society of Contact Dermatitis

This report reviews individual‐related variables (age, sex, race, anatomical site. skin surface properties), intra‐ and interindividual variation (temporal, physical and mental activity, orthostatic effect, menstrual cycle/menopause), environment‐related variables (light conditions, temperature) and various instrument‐related variables that influence skin colour. CIE colorimetry (Minolta Chroma Meter) and spectrophotometric measurement (Derma Spectrometer) are considered. The guidelines give recommendations for measuring conditions and procedures.

Comparison of Narrow-Band Reflectance Spectrophotometric and Tristimulus Colorimetric Measurements of Skin Color

Two types of portable reflectance instruments, tristimulus colorimeters (Chroma Meter CR-200) and narrow-band spectrophotometers (Dermaspectrometer), have recently become available for the quantification of skin color. In order to know the difference and the relationship between the different color systems, the CIE L*a*b* system and the erythema melanin (E/M) indices, respectively, adopted by the two, the variations in skin color were measured at 23 different anatomical sites of 10 healthy Caucasian male subjects. The reddish tint of the skin color of the face, palm and sole was readily detected by either of them in the increase in the a* value or in the E index, and a strong linear correlation (r = 0.92, p < 0.001) was noted between the two values. The fair color appearance of the trunk was detected in the high L* value and in the low M index, but the correlation between the two was much less significant (r = -0.56, p < 0.001). Although the mean b* values were highest in the trunk, they are significantly lower on the non-light-exposed side than those on the light-exposed side of the arm. The correlation between the b* value and the M index was weak.

Derivation and clinical application of special imaging by means of digital cameras and Image J freeware for quantification of erythema and pigmentation.

Background: Quantification of erythema and pigmentation is useful for analysis of skin tests and management of skin diseases. However, reflectance instruments for this purpose suffer from many technical and financial disadvantages. The aim of this study was to establish a method for evaluation of the amounts of haemoglobin and melanin using ordinary digital cameras and Image J freeware.

Effective inhibition of melanosome transfer to keratinocytes by lectins and niacinamide is reversible.

Abstract:  Skin pigmentation results in part from the transfer of melanized melanosomes synthesized by melanocytes to neighboring keratinocytes. Plasma membrane lectins and their glycoconjugates expressed by these epidermal cells are critical molecules involved in this transfer process. In addition, the derivative of vitamin B3, niacinamide, can inhibit melanosome transfer and induce skin lightening. We investigated the effects of these molecules on the viability of melanocytes and keratinocytes and on the reversibility of melanosome‐transfer inhibition induced by these agents using an in vitro melanocyte–keratinocyte coculture model system. While lectins and neoglycoproteins could induce apoptosis in a dose‐dependent manner to melanocytes or keratinocytes in monoculture, similar dosages of the lectins, as opposed to neoglycoproteins, did not induce apoptosis to either cell type when treated in coculture. The dosages of lectins and niacinamide not affecting cell viability produced an inhibitory effect on melanosome transfer, when used either alone or together in cocultures of melanocytes–keratinocytes. Cocultures treated with lectins or niacinamide resumed normal melanosome transfer in 3 days after removal of the inhibitor, while cocultures treated with a combination of lectins and niacinamide demonstrated a lag in this recovery. Subsequently, we assessed the effect of niacinamide on facial hyperpigmented spots using a vehicle‐controlled, split‐faced design human clinical trial. Topical application of niacinamide resulted in a dose‐dependent and reversible reduction in hyperpigmented lesions. These results suggest that lectins and niacinamide at concentrations that do not affect cell viability are reversible inhibitors of melanosome transfer.

Use of Cutometer area parameters in evaluating age-related changes in the skin elasticity of the cheek.

The decrease of skin elasticity on the cheek is a major concern to woman. The Cutometer® has been widely used to evaluate skin elasticity and its change with aging. Cutometer parameters derived from one suction have been traditionally used to evaluate skin elasticity, and few reports describe the use of multiple suctions to obtain parameters to assess the skin elasticity of the cheek. To find the most suitable Cutometer parameter that reflects age‐related changes in the elasticity of cheek skin using multiple suctions.

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.

Quantification of erythema and pigmentation using a videomicroscope and a computer

We report a method for quantitative analysis of erythema and pigmentation using a videomicroscope interfaced with a computer. The analysis was carried out by examining the brightness intensity of every picture element, composed of an image picked up from each band of red, green, and blue, and by deriving the quasi‐absorbance value (absorbance index) from the mean brightness for each band. In assessments of UV‐induced erythema and tanning, excellent linear correlations were found between the results obtained with our system and those with a narrow‐band reflectance spectrometer. Moreover, the absorbance indices of haemoglobin and melanin solutions showed linear relationships with their concentrations in in vitro examination. As the monitored picture becomes out of focus if incorrect pressure is exerted on the skin, and as regions of interest can be chosen from a magnified image, this system offers excellent interobserver reproducibility, and is suitable for the evaluation of erythema or pigmented lesions which are too small or irregular to quantify by conventional methods such as colorimetry.

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.

The influence of cutaneous factors on the transcutaneous pO2 and pO2 at various body sites

Summary The transcutaneous partial pressures of oxygen (tcpO2) and carbon dioxide (tcpCO2) were measured at eight different sites in 10 adult male subjects with an electrode at a temperature of 44°C. The mean tcpO2 values (mmHg) were significantly lower on the face (forehead 26·6, cheek 29·6) and the palm (26·4) than at other sites (60·6–69·6), The tcpCO2 values (mmHg) were only slightly higher on the face. Removal of the stratum corneum produced an average increase of the tcpO2 on the palm of 37·6 mmHg and on the forehead of 19·6 mmHg. However, in 10 children with an age range of 3–9 years, the difference in the mean pO2 between the cheek and forearm was very small. There was no significant difference in the cutaneous blood flow at 44°C between the cheek, palm and forearm.

Ultrasound enhanced skin‐lightening effect of vitamin C and niacinamide

Background/purpose: Cutaneous hyperpigmentation occurs in multiple conditions. There is a strong need for the improvement of hyperpigmentation especially among Asian women. However, the effect of existing skin‐lightening agents is not sufficient. One reason attributes to the limited capability of active agents to be delivered transepidermally. Ultrasound is one promising approach to enhance transepidermal transport. In this work, we investigate the effect of the use of high‐frequency ultrasound together with coupling gel containing skin‐lightening agents (ascorbyl glucoside and niacinamide) on facial hyperpigmentation in vivo in Japanese women.