ABSTRACT
Hyperpigmentation is one of the key phenomena observed on photo-damaged skin that has been exposed to sunlight for long term (1). Of particular concern, from a cosmetic point of view, are the common benign brownish hyperpigmented spots of the middle-aged and elderly, namely solar lentigo (2), as they can detract from overall skin appearance (3). Although not related to sun-damaged skin, epheledes (freckles) and postinflammatory hyperpigmentation (frequently caused by acne) are also scattered, brownish hyperpigmented spots of concern, especially to young adults. These hyperpigmented spots are common skin lesions for all peoples of the world, but are of particular concern for those of the Asian descent (4-8). As expected, therefore, cosmetic formulations claiming efficacy in skin lightening and reduction of hyperpigmented spots are popular products in Asia. Frequently, however, clinical trials to evaluate the effects of these skin-lightening ingredients have been evaluated by inspection, as we do not have reliable systems for measuring the degree of hyperpigmented spots of the face in an objective and quantitative manner. We developed here a highly reliable image analysis system to measure the total area of hyperpigmented spots and skin color tone in a wide area of the face. To quantify overall improvement of the hyperpigmented spots by application of a skin-lightening product, we conducted split-face clinical studies using this system.
