J. $oc. Cosmet. Chem. 27, 155-161 (1976) ¸ 1976 Society of Cosmetic Chemists of Great Britain A study of damaged hair V. N. E. ROBINSON* Synopsis--A SCANNING ELECTRON MICROSCOPE study of the morphological changes in human HAIR has revealed that these changes may be entirely attributable to the ABRASION normally associated with hair grooming. In particular, SHAMPOOING and BRUSHING can produce all of the observed changes detected in virgin hair. These changes are more deleterious in some cosmetically altered hairs. This appears to be attributable to a decrease in the disulphide bond content of these fibres, this decrease being brought about by the cosmetic treatment. INTRODUCTION In a study of fine changes in the surface architecture of human hair due to cosmetic treatment, Swift and Brown (1) have illustrated the stages of breakdown of human hair during cosmetic treatments. The natural appearance of hair, when first formed, displays a scale structure with smooth edges. This is subsequently transformed into stages they have characterized by: jagged scale edges, partial scale erosion, complete scale erosion, fibre splitting into two roughly hemi- cylindrical components and gross longitudinal splitting into many fibrous elements. These changes are generally referred to as weathering and the pre- dominant cause is thought to be exposure to sunlight (2), which may result in a variation of the chemical and physical properties from the root to the tip of the fibres (3, 4). By means of before and after treatments and the examination of the same hair fibres in the SEM, Swift and Brown (1) have established that some of these * School of Textile Technology, University of New South Wales, P.O. Box 1, Kensington, NSW 2033, Australia. 155

156 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS variations are due to combing of the hair and concluded that some may be due to natural weathering processes. They have also briefly mentioned some of the changes introduced into hair by perming and bleaching treatments. In a series of dynamic in situ experiments in a scanning electron microscope, Brown and Swift (2) have further demonstrated the deleterious effects of combing out tangles in hair. Such combing can cause cuticle cell lifting in tightly-looped fibres, as well as snapping fibres transversely or through the initial formation of a longitudinal fracture, when excess tension is applied during the combing. In a study of the structure and properties of normal adult hair, Wall and Hunter (5) have similarly illustrated the production of jagged edges in the cuticle, and have shown features on the cuticle that they have attributed to sun and atmosphere exposure. DiBianca (6) has demonstrated many different types of damaged hair ends, but has not studied how these different types of damage occurred. Robbins and Kelly (7) have analysed the amino acid content of cos- metically-altered hair. They found that bleached and permanent-waved hair contained less cysfine than unaltered hair, and correspondingly more cysteic acid residues. Bleached hair also contained slightly less tyrosine and methionine than unbleached hair. Miyazawa, Nozaki and Tamura (8) have made a similar study of the amino acid composition of hair damaged by treatment with cold-waving and hair bleaching lotions. They have also observed a reduction in the cysfine content of human hair, with one bleaching condition reducing the cystinc content from the normal of 13.9•o to 5.0•o, corresponding to an approximately 64•o reduction in the disulphide bond cross-linking of the protein molecules. These studies have illustrated the extent of chemical changes and the mag- nitude of physical changes introduced to hair, but have not yet confirmed how these observed physical changes were introduced. There is a need to understand how and why these deleterious physical changes to hair fibres occur in order to be able to prevent the damage. Some of this information is presented in this study. EXPERIMENTAL Samples of Caucasian hair were used in this study. This hair included many fibres displaying various degrees of splitting and hair damage, and samples that displayed no damage visible to the unaided eye. No attempt was made to differen- tiate between hair of different texture or condition. The fibres were mounted on stubs so that the tip, root and portions of the mid shaft of each fibre could be examined in a scanning electron microscope (JSM2). The mounted fibres were coated with approximately 500 3, of gold prior to examination. They were examined for variation of scale structure along and between fibres, extent of scale damage and removal and degree of splitting of ends. The findings were correlated with the known history of the hair, and