The color of the skin, and of any object, depends on the wavelength of the light and the optical characteristics of the surface. Different chromophores, mainly hemoglobin and melanin in healthy skin, absorb different wavelengths of light. Detailed insight into the complex optical principles of the skin and chromophores is provided by Pierard and by Kollias (11,12). Measurement of skin color reflectance is a suitable method for erythema quantification in addition to clinical assessment. It has been applied frequently in the grading of contact dermatitis and irritant and allergic patch-test reactions (13). Its value has also been proven in studies on the vulvar skin with respect to erythema quantification in irritant contact dermatitis (7). Skin color reflectance is especially suitable for serial measurements and also can be used for ethnic skin (14,15). However, the sensitivity of an experienced dermatologist's eye may still be superior to instrumental erythema quantification (12).
In contrast to the spectrophotometric method, which uses broadband (scanning) or selected wavelengths, the Minolta Chroma Meter (Minolta Chroma-Meter CR-300®, Minolta, Osaka, Japan) is a tristimulus colorimeter, which refers to the recommendations of the Commission Internationale de l'Eclairage. Color is expressed in a three-dimensional coordinate system, in terms of three units: L* (luminance/brightness) (white-black), a* (red-green), and b* (yellow-blue) (Fig. 1). a* represents the red-green axis with +100 expressing full red and — 100 expressing full green (13). The Chroma Meter is equipped with a polychromatic xenon flashlight for the illumination of the skin area and is easy to handle. Prior to the measurements, the instrument must be calibrated. As the genital skin color is influenced by the modulations of cutaneous blood flow, caused by temperature, orthostatic effects, the emotional white white
red yellow green red
Was this article helpful?
Rosacea and Eczema are two skin conditions that are fairly commonly found throughout the world. Each of them is characterized by different features, and can be both discomfiting as well as result in undesirable appearance features. In a nutshell, theyre problems that many would want to deal with.