24 D.M. Bryce et al. 12 Onoda, T. and Saito, H. Influence of a new antibacterial agent, Bronopol,upon the growth of cultured cells. Chemotherapy (Tokyo) 22 196 (1974). 13 Hale, L. J. and Inkley, G. W. A semiautomatic device for multiple inoculation of agar plates. Lab. Pract. 14 452 (1965). 14 Bryce, D. M. and Smart, R. The preservation of shampoos. J. $oc. Cosmet. Chem. 16 187 (1965). 15 Brown, M. R. W. Turbidimetric method for the rapid evaluation of antirnicrobial agents - Inactiva- vation of preservatives by non-ionic agents. J. $oc. Cosmet. Chem. 17 185 (1966). 16 Stretton, R. H. and Manson, T. W. Some aspects of the mode of action of the antibacterial com- pound Bronopol (2-bromo-2-nitropropane-l,3-diol). J. appl. Bact. 36 61 (1973). 17 King, M. B., Knox, R. and Woodroffe, R. C. S. Investigation of antituberculous substances- an agar diffusion method using Mycobacterium smegmatis. Lancet i 573 (1953). 18 Kabay, A. Rapid quantitative microbiological assay of antibiotics and chemical preservatives of a non-antibiotic nature. AppL Microbiol. 22 752 (1971). 19 Moore, D. H., Chasseaud, L. F., Lewis, J. D., Risdall, P. C. and Cramp(on, E. L. The metabolism of the antibacterial agent Bronopol (2-bromo-2-nitropropane-l,3-diol) given orally to rats and dogs. Fd. Cosmet. Toxicol. 14 183 (1976). 20 Moore, D. H., Chasseaud, L. F., Bucke, D. and Risdall, P. C. The percutaneous absorption and disposition of the antibacterial agent Bronopol in rats and rabbits. Fd. Cosmet. ToxicoL 14 189 (1976). 21 Noakes, D. N. and Sanderson, D. M. A method for determining the derreal toxicity of pesticides. Brit. J. Indust. Med. 26 59 (1969). 22 Stevens, M. A. Use of the albino guinea-pig to detect the skin sensitizing ability of chemicals. Brit. J. Ind. Med. 24 189 (1967). 23 Marzulli, F. N. and Maibach, H. I. Antimicrobials: experimental contact sensitization in man. J. $oc. Cosmet. Chem. 24 399 (1973). 24 Marzulli, F. N. and Maibach, H. I. The use of graded concentrations in studying skin sensitizers: experimental contact sensitization in man. Fd. Cosmet. ToMcol. 12 219 (1974). 25 Maibach, H. I. Dermal sensitization potential of 2-bromo-2-nitropropane-l,3-diol (Bronopol). Con- tact Dermatitis 3 99 (1977). 26 Schuster, G. Die Conserviemng von Shampoos und Schaumbademitteln. $eifen-Ole-Fette-Wachse 99 489 (1973). 27 Tuttle, E., Phares, C. and Chiostri, R. F. Preservation of protein solutions with 2-bromo-2-nitro- 1,3-propanediol (Bronopol). Am. Perfum. Cosmet. 85 87 (1970). 28 Barnes, M. and Denton, G. W. Capacity tests for the evaluation of preservatives in formulations. Soap, Perrum. Costa. 42 729 (1969). 29 Parker, M. S. Some aspects of the use of preservatives in combination. Soap, Perfum. Costa. 46 223 (1973). 30 Proserpio, G. Protection des cosm6tiques par des m61anges synergiques de pr6servateurs •i dosage microbiocide. Parrum. Cosmet. $avons 2 305 (1972). 31 Jacobs, G., Henry, S. M. and Cotty, V. F. The influence of pH, emulsifier, and accelerated ageing upon preservative requirements of o/w emulsions. J. Soc. Cosmet. Chem. 26 105 (1975).

J. $oc. Cosmet. Chern. 29 25-29 (1978) Towards objectivity in the assessment of eye irritation R. HEYWOOD and R. W. JAMES Huntingdon Research Centre, Huntingdon, PE18 6ES Synopsis The assessment of eye irritation is subjective. The eye test system is subject to such wide variation that it will never be possible to make precise measurement of irritancy. Clinical appraisal, supported by measurement of comeal thickness and intra-ocular pressure, is probably the best that can be achieved. The use of local anaesthetics should be considered when carrying out eye irritation tests in the rabbit. INTRODUCTION The assessment of eye irritatation is basically subjective and it is not surprising that the literature abounds in results showing different inter- and intra-laboratory values. The need for objective assessment has been voiced by many investigators and some para- meters for the measurement of functional and pathological change have been proposed. The purpose of this paper is to review the feasibility of some of these methods. CLINICAL EXAMINATION The assessment of irritants is based on the well-established Draize test- Draize, Woodard and Calvery (1)- which has been modified over the years, although most laboratories follow the standard procedure laid down by the U.S.A. Code of Federal Regulations (2). Albino rabbits of either sex weighing between 2 and 3 kg are the usual test species. It must be pointed out that differences due to age, sex, management, strain, season and other environmental factors have received scant attention, although there is little doubt that the strain of rabbit is of considerable importance. The degree of damage induced is dependent on the concentration of compound and the intimacy and duration of contact with the conjunctiva and cornea. The concentration of compound used should be that which induces a minimal measurable response. The intimacy of contact can be controlled by applying a known volume and standardising the application procedure. The other factor that could be varied is the period of contact between the test material and the conjunctival sac. It has been shown by Davies, Kynoch and Liggett (3) that 10 sec is the maximum delay time, after which irrigation is not beneficial. This initial contact time is too critical to control and it is inappropriate to introduce a washout technique and so add another variable to what is already a compli- cated situation. Another factor against initiating washout techniques is the fact that the washing procedure is not always beneficial. Sebaugh et al. (4) showed that the washing procedure shortened the onset of opacities produced by weak acids, but with 1•o 0037-9832/78/0100-0025 $02.00 ¸ 1978 Society of Cosmetic Chemists of Great Britain 25