A STUDY OF DAMAGED HAIR 161 Hydrogen bonds represent another useful form of cross-linking. Hydrogen bonds are reversibly broken every time hair is wet and are reformed again when it dries. Because of the decrease in hydrogen bonding, wet hair is completely unmanageable. Observations made during this study have indicated that wet hair is far more susceptible to damage during grooming than dry hair, and it would thus appear that minimal handling and brushing of wet hair could reduce the extent of physical damage to the hair. CONCLUSION This study has shown that the mechanical deterioration of hair which results in the production of split ends can be entirely attributable to the abrasion associated with hair grooming. It has also indicated that the increased tendency of hair to split after cosmetic treatments, particularly perming and bleaching, appears to be due to a reduction in the cross-link content of the fibres. To prevent this mechanical damage minimum brushing and shampooing would appear to be desirable. Prevention of damage to the disulphide bond content of the hair fibres would also appear to be desirable to reduce splitting and improve the manageability of hair. There would also appear to be some advantages in increasing the cross-link content of hair by the introduction of cross-linking molecules. The additional cross-linking would retard fibre swelling when wet and possibly increase the wet abrasion resistance of the hair. It is also possible that such a treatment would improve the manageability and condition of the hair as well as being able to impart a permanent change of shape to the fibres. Studies in these directions are continuing. (Received: 24th February 1975) REFERENCES (1) Swift, J. A. and Brown, A. C. The critical determination of fine changes in the surface architecture of human hair due to cosmetic treatment. J. Soc. Cosmet. Chern. 23 695 (1972). (2) Brown, A. C. and Swift, J. A. Hair breakage: the scanning electron microscope as a diag- nostic tool. J. Soc. Cosmet. Chern. 26 289 (1975). (3) Robbins, C. Weathering in human hair. Text. Res. J. 37 337 (1967). 4) Robbins, C. R. and Kelly, C. H. Amino acid composition of human hair. Text. Res. J. 40 891 (1970). (5) Wall, R. A. and Hunter, L. D. Normal adult hair--structure and properties. Cosmet. Perrum. 893 (1974). (6) DiBianca, S. P. Innovative scanning electron microscopic techniques for evaluating hair care products. J. Soc. Cosmet. Chern. 24 609 (1973). (7) Robbins, C. R. and Kelly, C. H. Amino acid analysis of cosmetically-altered hair. J. Soc. Cosmet. Chern. 20 555 (1969). (8) Miyazawa, F., Nozaki, F. and Tamura, T. Studies on damaged hair. Proceedings 8th Inter- national Congress IFSCC, London. C8 (1974) (Blackwell Scientific Publications, Oxford). (9) Feughelman, M. and Chapman, B. M. The swelling of wool fibres with reduced disulphide content in 98 % formic acid. Text Res. J. 36 1110 (1966).

J. Soc. Cosmet. Chem. 27 163-208 (1976) ¸ 1976 Society of Cosmetic Chemists of Great Britain Analytical aspects of potentially risk-bearing substances in cosmetics D. H. LIEM* Presented at the IFSCC VIIth International Congress on 'Cosmetics--Quality and safety' organized by the Society of Cosmetic Chemists of Great Britain at London on 26-30th August 1974 Synopsis--Analytical surveys have been made in the last three years to obtain a clearer picture of the use of POTENTIALLY RISK-BEARING SUBSTANCES in cosmetics in furtherance of COSMETIC LEGISLATION in the Netherlands. EYE MAKE-UP COLOURS have been identified by a set of characteristic standard reactions. LIPSTICK COLOURS were identified by well-known CHROMATOGRAPHIC methods. Colour intermediates for the OX!DATIVE HAIR COLOURINGS were identified by two-dimensional THIN-LAYER CHROMATOGRAPHY of the unpurified extract and the aromatic amines confirmed by glc analysis, which also permitted quantitative determination. A GAS-LIQUID CHROMATOGRAPHY separation of phenolic intermediates is also described. SUNTAN PREPARATIONS were analysed for the presence of uv-absorbers, BROWNING AGENTS and local ANAESTHESICS. A simple AEROSOL sampling method, prior to glc analysis, has been developed, thus permitting a total analysis of solvents and propellants in single liquid phase aerosols within an hour. Analytical data of market samples is also presented. INTRODUCTION Analytical data gives a picture of the use of potentially risk-bearing sub- stances in cosmetics, which might be different from literature and textbook sources. At the time the Dutch Cosmetic Bill became valid in September 1968 not * Government Food Control Station, H. B. Blijdensteinlaan 2, Enschede, Holland. 163