BACTERIOLOGICAL AND DERMATOLOGICAL TESTING OF COSMETICS 151 mals. Very small amounts are used and the results obtained, if positive, give a very good indication that the compound contains primary irri- tants. Comparison of the results of this test with short duration patch tests such as the United States Navy skin irritation test or the soap manu- facturers' patch test have indicated that this method is just as reliable. It is also much easier to apply and the results are obtained in a much shorter time. The eye irritation test consists in dropping a couple of millimeter cubes of the cosmetic on a rabbit's eye and then examine the degree of irritation so obtained. When these preliminary tests, intraperitoneal test or eye irritation tests, give a negative result, i.e., when no skin irritants are detectable we also con- duct a patch test. Whenever possi- ble we follow the method of Drs. Louis Schwartz and Samuel Peck which we have found to be the most suitable for the greatest number of cosmetics. It consists in applying the cosmetic on human skin for a period of five days. If the cosmetic is in solid form it is applied as is if it is liquid it is tested by soaking a freshly boiled-ofF and sterilized piece of gauze in the solution to be tested. The patch is covered by means of water-proof surgical tape and re- moved at the end of a period of five days. The skin is then observed for the presence of skin irritation that very day and the following two days. Ten to fifteen days after the removal of the first patch another patch is applied for forty-eight hours after which the skin is observed that day and the following tlvo days. The presence of skin irritation caused by this second patch indicates 't, at the cosmetic so tested is a cutaneous sensitizer. These tests are conducted first on 50 people. When five or more individuals show an irritation the test is considered as being com- pleted and the cosmetic is reported as being a primary irritant. When two or less than two individuals show a reaction, the test is com- pleted to a greater number of indi- viduals never to be inferior to 200. These tests may probably look too severe but they are not. We have found a great many cosmetics that, when tested prior to marketing, were found to contain either primary irritants or cutaneous sensitizers, or both. It was definitely easier for the manufacturer to change his formula before launching the cosmetic than to market it without testing and face a great many costly lawsuits against which he would have had no defense. (2) Tr. STS •oR Ptm•T¾ Very often cosmetics which have irritating properties contain impuri- ties. This is not always the case, but it is nevertheless advisable to have purity tests conducted on all types of cosmetics. In the spirit of the Food, Drugs and Cosmetic Act, the purity of a compound comes next to its harmlessness. The first step in conducting purity tests on cosmetics is to make bacterial and fungal counts. Every manufacturer will agree that if two cosmetics con-

152 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS tain very similar, not to say identi- cal compounds• the one which will have the lowest bacterial and fungal counts will be of better grade and consequently have more merchan- dising value. We have found amaz- ingly high counts in cosmetics, so high that some of them almost defy comparison with any other polluted source of bacterial or fungal life. On the other hand, a great many cos- metic chemists have during the past years endeavored to produce cos- metics that were of a great bacterio- logical purity and sometimes even germ and fungus free. This state of purity is verified by conducting a sterility test according to the method described in the U. S. Phar- macopoeia. According to the test method, a cosmetic is sterile after it is placed with aseptic precautions in a tube of sterile broth and kept at a temperature of 7 ø C. for seven days, the tube does not show any growth and remains crystal clear. Sterility tests are of course impor- tant when cosmetics may be ab- sorbed in the digestive tract. (3) T•.sts Some cosmetics pass the purity test described above immediately after they are manufactured and for a short period of time. Then, when their shelf life begins in department or drugstores, their bacterial and fungal count increases to amazing heights. In order to remedy this cause of deterioration, cosmetic chemists add preservatives to their formula with the result that the shelf life of their products is greatly increased. It is always very wise to test the value of the preservatives contained in these cosmetics. This is generally done by measuring the bacteriostatic and fungistatic prop- erties of the cosmetic itself. Very often we are asked to first test the compound which the chemist plans to use in order to determine the con- centration at which it should be added to the formula. Bacterio- static and fungistatic tests are very simple and rapid and are conducted according to the method of the Fed- eral Department of Agriculture. These properties are verified by plating the sample of the product in Petri dishes planted with bacteria or fungi and measuring the width of the zone of inhibition where the bac- teria or fungi do not grow on the plates. A cosmetic is said to be bacteriostatic when it inhibits the growth of bacteria, and fungistatic when it inhibits the growth of fungi. Needless to say, these preservatives should be tested for toxicity, skin irritants, and cutaneous sensitizers at the concentration at which they are to be used in the cosmetic prior to being incorporated in the formula. We have tested more than 375 germicides-fungicides capable of be- ing used as preservatives in cosmet- ics because of their bacteriostatic and fungistatic properties. When each were patch-tested at the con- centration where they did meet the requirements of the cosmetic chem- ists, they were found to be highly irritating, or sensitizing, to such an extent that out of this huge number of various compounds less than a