JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (Facing p. 340)

EVALUATION OF SKIN BLEACH CREAMS 341 Measurements of skin lightness were made by holding the wedge alongside the animal and noting the step numbers which most nearly matched each site. The time course of depigrnentation produced by the four products is shown in Fig. 2 where each point is the mean of four observations. Product A was apparently the most effective of the products tested since it produced a more rapid and a greater degree of depigrnentation than the other creams which were all similar in performance. It was noted however that this pro- duct (Product A) was also somewhat irritant, producing more scaliness than the other products and so giving a false impression of enhanced whiteness. One noticeable feature of tests of this sort carried out on black guinea- pigs was that the maximum lightening effect was achieved after about 15 days. 6.ø I 4'0 3'0 2.0 I-O I I I I I I 0 5 I0 15 20 2.5 .30 Doys Figure 2. Time course of depigmentation on black-skinned guinea-pigs--wedge technique. TESTS ON BLACK-SKINNED SWINE Whilst the guinea-pig is a suitable animal for screening large numbers of compounds, it was considered advisable to obtain comparative data on at least one other black-skinned species other than man. It was not easy to find another suitable species since most animals with black hair have, in fact, white skin. The pig appeared to be a satisfactory choice for a number of reasons.