Almost all women have a desire to maintain smooth and soft hands. Particularly in Japan, where “dry chapped hands” is a great nuisance for women in their daily life, and an important problem which cosmetic scientists should solve. The purpose of this study was to clarify the process whereby the hands become dry and chapped, and to develop the preventive cosmetics for it.
Our survey showed that the skin was most chapped on the thumb, index finger and middle finger and in the upper extremities of the fingertips. The characteristics of dry, chapped fingertips were investigated through methods of dermatophysiology and histopathology (scanning and transmission electron microscopy etc.). It was found that the functional damage of sweat glands and parakeratosis were important key points with respect to the onset of chapped fingertips.
In order to examine dry chapped fingertips in detail, a method of counting the number of active sweat glands was developed to evaluate their function objectively. Also, quantitative methods using image analysis of microscopic patterns of fingerprints and amount of scales, were developed as objective evaluation of parakeratosis. These new quantitative methods helped the study to find ways to prevent dry chapped hands.
In the course of the studies described above, effective substances and methods to protect corneum cells and sweat glands from the damage of detergents were investigated. These studies showed that condensed tannin extracted from persimmon (Diospyros Kaki Linn.), forms a protective membrane on the fingers and sweat gland walls, and it is remarkable in preventing skin from becomming chapped. Subsequently, stabilization of persimmon tannin against oxidization and heat was successfully achieved. It was concluded that persimmon tannin is an effective in-gredient for daily hand-care cosmetics.
