DIAGNOSIS OF COSMETIC DERMATITIS 5 SuN-TAN PREPARATIONS Dermatitis has not been reported from sun-tan preparations. This does not mean that it does not occur. It may be attributed to the sun. When a well-known sun-tan prepa- ration properly used does not pro- tect a patient against the burning solar rays, or when a patient using a sun-tan preparation develops a severe case of sunburn which per- sists for a week or longer, the physi- cian should suspect the preparation. Patch tests should be performed on covered parts of the body, the back or thighs, and the reaction read be- fore the part is exposed to sunlight. The diagnosis of dermatitis from cosmetics in the majority of cases, is not difficult to the dermatologist who is familiar with the ingredients used in cosmetics, and in most in- stances, the actual irritant can be found. But in some cases, not only a thorough knowledge of cosmetics and dermatology, but also the in- genuity and persistence of a Hohnes are required, to discover the actual cause of a suspected case.of cosmetic dermatitis.

COLOR MATCHING IN THE COSMETIC INDUSTRY* By E. I. ST• ^RNS Research Department, Calco Chemical Division, •tmerican Cyanamid Company, Bound Brook, N. •. THREE physical factors enter into every appearance of color. These factors are: the light which illuminates the sample the object itself which is seen and the eye which transmits to the brain the sensation of color. The psycholo- gist may disagree with this and say that the mind may have a concept of color even in the absence of light. The physicist may disagree with this and say, that an object has color even though there is no observer present to discern it but without getting into these philosophical dis- cussions, let us examine these three factors more closely and see how they are related to the sensation of color. The importance of the illumina- tion is easily demonstrated. If a red lipstick is held in white light, the eye receives a sensation of red. On the other hand, if the red lipstick is viewed in green light, the red lip- stick will appear black. Illumina- tion is, therefore, an important fac- tor in the discernment of color. Even so-called white light is not always white, and daylight itself cannot be taken as a standard white * Presented at the May 15, 19•,6, Meeting, New York City. 54 light, because it is so variable. Light from the north sky is very blue in color compared with light from the southern sky. Direct sunlight is quite yellowish in color, but as sunlight passes through the atmosphere, some of the light is scattered sideways. When a sam- ple is viewed with north sky light, the illumination is not direct sun- light, but is the sideways scattered radiation. This sideways scattered radiation is quite bluish in color, and in fact it is this which gives the blue appearance to the sky. It is . thus possible for two samples to look alike on the south' side of the building where they are illuminated by direct sunlight, but to appear quite different when they are viewed by north sky light on the north side of the building. The color of,day- light is not only variable depending upon whether the north or south sky is used to illuminate the sample, but also it varies from day to day because of cloudiness and other fac- tors in the atmosphere, and it varies over one day from morning to night. If one wishes to make any scientific calculations on color, as viewed in daylight, it is necessary to define what is meant by daylight. This