EVALUATION OF EFFICACY AND SAFETY OF COSMETICS 25 decomposition is an important fac- tor, particularly for creams. Is the product actually bacteriostatic and fungistatic? Will it inhibit the growth of typical bacteria and fungi under optimum conditions for their growth? Failing that, will these organisms grow in the product itself if it is inoculated with them? Many headaches due to mold growth and rancidity in jars could have been prevented if these relatively simple tests had been run. We have had liquid products that were perfectly stable as long as the bottle was un- opened, but that soon developed a foul odor on opening and partially removing the contents, due to aerobic, air-borne organisms which would only grow when air was admitted. Pigmented cosmetics are tested for their relative opacity and cover- ing power. Nail polishes and lac- quers are tested for their light re- flectance and for their drying time, adhesion to metal and other sur- faces, and for flexibility of the dried film. Cake make-up is tested for its adhesion to leather, simulating skin, and for its ease of removal by soap and water as well as by cleans- ing creams. Many other tests are devised as a method of evaluating the comparative performance of various products. Sun-tan lotions, although legally drugs, are more often thought of as cosmetics. Their effectiveness de- pends on their ability to absorb the erythema-producing ultra-violet waves of sunlight, in the band be- tween 2900 and 3200 Angstrom units. It is only the rays within these wave-lengths that produce sunburn and which should be screened out. Since these same wave-lengths are the ones that pro- duce tanning, it is not desirable to exclude them entirely, but only to reduce them by about 75 to 90 per cent. Ultra-violet absorption curves are run on these products, in a quartz cell in a film thickness of 0.02 ram., which is the usual thickness of the film on the skin. Some sun-screen- ing agents may be very effective in absorbing ultra-violet rays, but may be totally unfit for use in a sunburn preventive, because they are rapidly destroyed by the longer wave- lengths in sunlight and would rapidly lose their effectiveness on the beach. For this reason, the ultra- violet absorption curve is again run after exposing the product in the quartz cell to the action of four hours of sunlight. These tests are comparative and must all be run simultaneously. Results obtained on one day cannot be compared with those obtained on another day. Deodorants and antiperspirants are other products which we usually think of as cosmetics, although anti- perspirants are actually drugs. A deodorant which merely masks the odor of perspiration with a more pleasant odor is difficult to test. This can be done by use of the osmo- scope, which is an instrument that utilizes the principle of diluting a given concentration of odor with air until a concentration is reached where the objectionable odor is

JOURNAL OF THE SOCIETY .barely perceptible. This is called "the threshold of perception of odor" and is assigned a numerical value known as the pO value. If two test pieces of gauze are worn under both armpits of several sub- jects for the same length of time, one axilla with and the other without a deodorant, it is possible to evaluate the effectiveness of the deodorant by the difference in the pO values. These tests are open to subjective influence, and great care must be taken to conceal the identity of the test sample from the observer. Most deodorants that are not anti- perspirants depend for their effec-' riveness on the fact that they pre- vent bacterial decomposition of per- spiration. The objectionable odor is due almost entirely to metabolic products produced by bacterial de- composition, since fresh perspiration has practically no odor normally. This type of deodorant is tested for its bacteriostatic properties. Anti- perspirant preparations may be evaluated in vitro by measuring their capacity to precipitate protein. Several in vivo methods have been purposed for determining antiper- spirant effectiveness on human be- OF COSMETIC CHEMISTS ings by measuring the amount of perspiration transpired from a given area in a given length of time. We have not had much success with any of these methods and we find it extremely difficult to duplicate re- suits. Any test requiring a diagnosis or evaluation of a skin condition is run in conjunction with a dermatologist. In order to avoid subjective influ- ence, the products are given code numbers. Neither the subjects nor the examining physician have any knowledge of the identity of the products or of the code system. Such tests are used to evaluate the relative effectiveness of hand creams, lotions, soaps, etc., where the original condition of the skin is compared against its condition after the use of a product or products for a definite period of time. In cases of doubt, the results are submitted to a consulting mathematician for statis- tical evaluation. , I have attempted to give you some of the highlights of safety and performance tests which consultants are frequently called upon to make on cosmetic products. There are others not mentioned here.