BLEACHING CREAMS will Bleaching Creams prove help- ful in the removal of blackheads help prevent externally caused pimples and secondary infection and will they fade freckles and lighten the skin ? We have been able to demonstrate successfully that the exfoliation produced by the application of Bleaching Cream and the friction of the wash cloth during the prescribed washing of the face before its application will help re- move blackheads. The antiseptic and germicidal value of the U.S.P. 5 per cent Ammoniated Mercury Ointment is well established. Its continued popularity for the treat- ment of skin disorders is evidenced by a recent study showing its pre- scription use and continued recom- mendation by standard dermatolog- ical textbooks •ø. The following studies on skin lightening were made independently by the National Toilet Company on its product, an advertised Bleaching Cream •. Jones 4, in his report on pigmentation, tells us that the colour of the human skin is dependent upon five factors: 1. The number of blood vessels present in the tissues and the degree to which they are filled with blood 2. The natural inherent colour of the materials which com- pose the skin cells 3. The pigment, carotin 4. Bile pigments 5. Melanin. We are interested only in Melanin, because it is the pigment which most strongly influences the colour of the skin--and because it is the pigment affected by Bleaching Cream. Melanin is formed in the basal or germinative layer of the epider- mis. As the cells move upward, the pigment begins to disappear and by the time they reach the stratum lucidum it has vanished entirely. It was originally believed that bleach- ing creams, by their property of speeding up the natural exfoliation of the skin, simply hastened nature's process of destroying melanin. We 'now have more knowledge of its formation and the action of Am- moniated Mercury in retarding it. Reports by Raper •2 Arnow •a, and Jones 4, have done much to enlighten us on the formation of melanin. It is possible that any one of three amino acids found in the skin may form the same end product-- melanin. These are Tyrosine, Phenyl- alanine and Tryptophane. According to these scientists, it is believed that the first step in human pigment formation is the conversion of tyrosine to dopa. This is brought about by ultra violet light or the enzyme tyrosinase. In 1917 Bloch 4 demonstrated that in man there is an enzyme, dopa oxydase, that con- verts dopa to dopa-quinone. By condensation we obtain 5:6 dihy- droxydihydroindole a carboxylic acid. This compound changes to the red pigment, hallochrome, which is converted to. 5:6 dihydroxyindole, a carboxylic acid. Melanin is formed when two or more molecules of this compound join together. Mercury prevents the formation of melanin by inhibiting the action of the enzy- mes, so that the first steps in this series of reactions do. not take place. When this happens, the formation 179

JOURNAL OF THE SOCIETY of pigment is retarded and the skin grows lighter. Our method of recording and measuring the skin lightening pro- duced by the use of Bleaching Creams depends upon photography. By it we obtain permanent records in the form of films and prints. We recorded the relative colour density of the skin by photographing it against a background composed of standards of known reflectance value, under carefully controlled, uniform conditions. We use a special apparatus in making our films. A circle is com- posed of neutral grey s,hades of known reflectance value, extending from actual black to actual white. The subject stands behind the circle and places her cheek against the opening in the centre, exposing ap- proximately 15 per cent of the area of that side of her face. The appar- atus and the camera are firmly fixed and the studio is light-proof. The illumination is at equal distances and at equal angles with a controlled voltage of 108 volts. We use super- sensitive panchromatic film, stop 11 and exposure of l/lOth second and the Wratten X-2 filter. .This combination of film, filter and illum- ination is recommended by Eastman for producing monochromatically the colours of the subject in the same relative value as the eye. would see them in daylight. A typical print made from one o.f our films shows a round central area which is actually the subject's• cheek. The segments around it are of measured reflectance, expressed 180 OF COSMETIC CHEMISTS in terms of Munsell Neutral Value Scale. This scale is a series of regularly graduated greys of known reflectance extending from actual black to actual white. Films like this are made of the right and left cheeks of each subject at the start of the test and after two, four and six weeks, which is the end of the test. Our films are then measured on a photovolt Densiometer Model 505 using the special illuminator designed particularly for measuring the den- sity of films. The skin area of the film is first measured and then the segments of known reflectance which are immediately lighter and immedi- ately darker. By linear interpolation we obtain the percentage of light re- flected from the skin, or percent re- flectance •4. Comparison of the percentages at the start and finish of the tests indicate if the skin is becoming lighter or darker. Thus we have a method of recording and measuring the relative colour density of the skin that is entirely independ- ent of comparisons made by the eye. For further simplification, we have also expressed our results in terms of shades. The validity of the term shades, or the just noticeable differ- ence in shades of neutral grey, is es- tablished by extensive experimental data published in 1933 by Munsell, Sloan and Godlove •. Our test procedure was compara- tively simple. The subjects• re- ported to our studio. daily where they carried out the routine under our observation and direction. The test groups washed their faces with a