j. Soc. Cosmet. Chem., 33,203-215 (July 1982) The effect of grooming on the hair cuticle SUSAN E. KELLY and V.N.E. ROBINSON, School of Textile Technology, University of New South [Vales, P.O. Box 1, Kensington NS[V, 2033, Australia Received July 20, 1981. Synopsis A study has been carried out on the effects of normal grooming on the cuticle of human hair. The grooming processes studied included shampooing, wet combing, wet brushing, and towel drying. The experiments were performed on tresses of hair and also included "on-head" studies. The results were assessed using scanning electron microscopy techniques. The data indicate that all of the damage normally observed can be entirely due to the grooming process. Sharnpooing and towel drying were shown to inflict some damage, but the process of wet combing or brushing greatly increased the damage. Brushing was shown to be more damaging than combing. The use of a conditioner was shown to significantly decrease this damage by reducing the friction forces generated in the hair during combing. INTRODUCTION Human hair consists of three main components: the cuticle, the cortex, and the medulla (1). Figure 1 shows transverse cross-sections of human hair which clearly illustrate the three components. The cuticle, which comprises the outermost layer, forms a protective sheath around the cortex. When the hair first emerges from the follicle the cuticle consists of between six and ten overlapping scales (1). These are clearly visible in Figure 1. As the hair grows away from the scalp it is subjected to various outside influences which can have a damaging effect on the cuticle. The scales, which are at first smooth and rounded, become rough and jagged as pieces are eroded away. If the hair is allowed to grow long enough and is sufficiently exposed to these degradative processes, then eventually complete removal of the cuticle layer will occur, leaving the cortex of the hair exposed (2-5). The unprotected cortex will then split and break very easily, which can lead to the appearance of split ends and often render the hair *'unmanageable." The progressive stages of damage to the cuticle are illustrated by the scanning electron micrographs of hair from root to tip given in Figure 2. The gradual erosion of cuticle scales has been attributed to various factors including aging, exposure to sunlight, handling, and the grooming processes to which hair is subjected which include shampooing, drying, brushing, and combing (1-6). Hair can also be damaged chemically by the application of treatments such as bleaching, coloring, and permanent waving which modify the hair (7), and it is likely that these treatments leave the hair more susceptible to further damage. 203

204 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS A c ß ß ', ' , 20pm Figure 1. Scanning electron micrograph of transverse cross-sections of human hair showing the three basic components: (A) the cuticle, (B) the cortex, (C) the medulla. The observation by Garcia et al. (2) of a pattern of cuticle wear related to the distance from the root relative to the overall length rather than simply to the distance from the root excludes age per se as a major factor in cuticle wear. This view is also supported by the observation of a lock of Jane Austen's hair by Swift (8). This lock was at least 150 years old and was thought to have received minimal handling. It was found to display minimal cuticle damage for most of its length. Studies of the effect of grooming have concentrated on the processes of combing and brushing. Swift and Brown (7) examined the same hair fibres before and after combing and found a cuticle removal rate of 5/am per 2000 comb strokes. They postulated that this accounted for some but not all of the observed cuticle damage, attributing the remainder to such factors as handling, exposure to sunlight, and washing. Later, Garcia et al. (2) showed that the pattern of cuticle removal from root to tip of hair fibres was similar to that of the forces present in the hair during combing. Both increased from root to tip as a function of the relative position along the hair with respect to its overall length. This would seem to indicate that the average rate of cuticle removal calculated by Swift and Brown (7) probably does not adequately account for the effect of combing as it does not take into account any variation in the forces along the length of the hair. In addition, the process of wet-combing out of knots after washing was not considered by them. Brown and Swift have examined the process of combing out knots directly under the scanning electron microscope (3). Definite lifting and breaking of the cuticle scales was observed by the tangling of hair during combing. A greater ease of splitting was observed at the tip end compared to the root end and this was attributed to the greater degree of weathering, i.e., exposure to sunlight, that had been received at the tips. Okumura et al. (6) have studied the physical and chemical damage done to hair by dry brushing. They observed that the cuticle scales were lifted away and stripped off by the