Micro-organisms on human skin 613 In practice, however, we noticed that the sealing of the 2 mm headpiece was in- sufficient, especially on hairy areas of the skin. The use of a good rubber sealing was also impossible, due to the high flexibility in relation to the small opening diameter. For this reason all further experiments were carried out with our standard 14 mm sprayhead with a total efficacy of 25•o. As mentioned before the axillae and the scalp are parts of our body, which are interesting for cosmetic research. The study of the microbial population of the axilla is important through the application of a deodorant product and the microflora of the scalp can be used to study the effect of an antidandruff preparation. For this reason we tested the features of the Water-Pik method on these areas. The microbial population of the axilla was determined by washing with 100 ml on five adjacent locations on each axilla. The complete quantity of washing fluid (500 ml) was collected and after homogenisation and dilution the number of aerobic micro- organisms was counted. The Water-Pik method gave fairly reproducible numbers of micro-organisms, as can be seen from Table III. Table Ill. Variation between individuals of the recovery of micro-organisms by a 14 mm head using the Water-Pik method Subject Totally recovered number of micro-organisms (14 mm head) 1 L 1-5 x 10 6 R 1.3 x 10 6 2 2.2 x 10 4 2.5 x 10 a 3 1.3 x 10 * 8.8 x 10 4 4 3'9 x 10 4 1'0 x 10 6 5 7'7 x 10 4 6'9 x 10 4 6 2'5 x 10 4 1'7 x 10 4 7 5'5 x 10 4 5'0 x 10 a In accordanee with the results of other investigators (26, 1), a big individual variation is shown in the number of the micro-organisms. Table III shows a good relationship between the population of the left and the right axilla, regardless of the magnitude of these numbers. For the sampling of the scalp also five times 100 ml with the 14 mm sprayhead was used. Here the total number of lipophylic micro-organisms was counted. In Table IV a survey is given of the scalp population of four subjects determined on several occasions. As it is hardly possible to sample twice on a scalp at the same time the reproducibility of our method on the scalp is difficult to give. While sampling bacteria from scalp and axillae by the Water-Pik method scales were dragged along from the skin surface with the fluid stream (27). These scales did not interfere with the microbiological figures, as the microcolonies in the scales appeared to be easily dispersed in the Triton wash fluid. This finding is in accordance with the experiments of Williams (1) in which was demonstrated that samples wash fluid only contain disaggregated organisms. In one of the long-lasting spray experiments on the axilla skin (Fig. 3), the micro- organisms in each fraction were identified. The types of micro-organisms agreed with

614 E. M. Staal and A. C. Noordzij Table IV. Time of sampling Total lipophylic micro-organisms/cm • on the scalp Subject 1 Subject 2 Subject 3 Subject 4 After 1 week 7'1 x 10 • 2-6 x 106 5.4 x 10 • 6-9 x 10 • After 2 weeks 1'9 x 10 • 1'4 x 106 5'8 x 10 • 4'4 x 10 • After 3 weeks 4-4 x 10 • 1-6 x 106 1.1 x 10 • 2-9 x 10 • After 4 weeks 3.8 x 10 • 1.7 x 106 1.9 x 10 • 9.4 x 10 • After 5 weeks 4.8 x 10 • 3.0 x 10 • 1.6 x 10 • 7.5 x 10 • those given in the literature (28, 29). We also noticed that the ratio between aerobic and anaerobic micro-organisms did not change as a function of the quantity of washing fluid. CONCLUSION The Water-Pik method has been tested as a method to quantify the number of micro- organisms in the axilla and on the scalp. In these areas of the human skin, which are important for the study of the effectiveness of a deodorant or antidandruff preparation, the Water-Pik method appeared to be a suitable tool. The Water-Pik method is easy to handle and gives little discomfort for the subjects. Not only for cosmetic research but also for medical or dermatological studies the described method can be recommended for the quantitative sampling of the skin popu- lation. REFERENCES 1 Williamson, P. Quantitative estimation of cutaneous bacteria. In: Maibach, H. I. & Hildick-Smith, G. Skin Bacteria and their Role in Infection. 3 (1965) McGraw Hill, New York. 2 Kligman, A.M. The bacteriology of normal skin. In: Maibach, H. I. & Hildick-Smith, G. Skin Bacteria and their Role in Infection. 13 (1965) McGraw Hill, New York. 3 Woodroffe, R. C. S. and Shaw, D. A. Natural control and ecology of microbial populations on skin and hair. In: Skinner, F. A. and Cart, J. G. The normal microbial flora ooeman. 13 (1974) Academic Press, London. 4 Marples, M. J. The normal microbial flora of the skin. In: Skinner, F. A. and Can', J. G. The Normal Microbial Flora of Man. 7 (1974) Academic Press, London. 5 Gibbs, B. M. and Stuttard, L. W. Evaluation of skin germicides. J. Appl. Bacteriol. 30 66 (1967). 6 Selwyn, S. and Ellis, H. Skin bacteria and skin disinfection reconsidered. Brit. Med. J. 1 136 (1972). 7 Parker, M. S. Skin bacteria: myth and reality. Soap, Perrum. Cosmet. 45 296 (1972). 8 Holt, R. J. Aerobic bacterial counts on human skin after bathing. J. Med. Microbiol. 4 319 (1971). 9 Holt, R. J. Pad culture studies on skin surfaces. J. Appl. Bacteriol. 29 625 (1966•, 10 Dixon, H. and Paneza, A. K. Microbiological applications of novel replipad skin sampler. J. Soc. Cosmet. Chem. 28 21 (1977). 11 McGinley, K. J., Leyden, J. J., Marpies, R. R., Path, M. R. C. and Kligman, A.M. Quantitative microbiology of the scalp in non-dandruff, dandruff and seborrheic dermatitis. J. Invest. Dermatol. 64 401 (1975). 12 Leyden, J. J., McGinley, K. J., Mills, O. H. and Kligman, A.M. Age related changes in the resident bacterial flora of the human face. J. Invest. DermatoL 65 379 (1975). 13 Shehadeh, N.J. and Kligman, A.M. The effect of topical antibacterial agents on the bacterial flora of the axilla. J. Investigative Dermatology 40 61 (1963) 14 Ulrich, J. A. Techniques of skin sampling for microbial contaminants. Health Lab. Sci. 1 133 (1964).