EMOLLIENT ACTION OF KUKUI NUT OIL 245 lotion as compared with half doses of the neat oils. In spite of the lower oil application rate with the lotion, by the fifth stripping among the three subjects, 735 --- 161 •g/strip of oil was left after kukui lotion application. This was not significantly less than with full-dose neat oil application but was significantly more than the half dose of neat oil. This point may be seen in another way in Figure 4. Compared with the oils, a larger percentage of the applied oil remained in the stratum corneum from the second through the fifth stripping with the lotion. Oil appeared to spread more evenly through the layers of skin with kukui lotion. Table II is a side bar showing fatty acids extracted from untreated skin of the three volunteers. It may be seen that there was variation in fatty acid profiles. The variations were consistent with the accepted notion that with fatty acids, one is what one eats. The strippings were consistent with self-reported dietary habits of the three individuals. In the mixed cultural milieu that is Hawaii, subject A reported eating a typical American diet except that fish was eaten twice a week on recommendation of the American Heart Association. The profile therefore contained traces of EPA (C20:5n-3) and DHA (C22: 6n-3), which are marine fatty acids, in a background containing high levels of oleate (C18:1n-9), linoleate (C18:2n-6), and linolenate (C18:3n-3), which may have come from plant oils in the subject's foods. Subject B reported having fish on the table every evening. Her profile contained substantial levels of marine fatty acids. Subject C's skin fatty acid profile contained high levels of saturated fatty acids. Subject C reported eating large amounts of beef and pork at a University of Hawaii dormitory. 20 15 10 2 3 4 5 6 stripping number Figure 4. Penetration of oils into the stratum corneum for kukui lotion (closed squares), coconut oil (open squares), and kukui oil (open triangles).

246 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II Fatty Acids in Strippings From Three Individuals • Subject A Subject B Subject C C 12 Laurate 7 1 16 C14 Myristate 6 10 10 Unknown 5 -- -- C16 Palmirate 20 24 35 C 16:ln-7 Palmitoleate 4 10 4 C 18 Stearate 8 5 21 C18:ln-90leate 23 14 7 C 18:2n-6 Linoleate 16 2 6 C 18:3n-3 Linolenate 13 __b 2 C18:4n-30ctadecatetraenoate -- 3 -- C20:ln-9 Eicosenoate -- 5 -- C20:4n-6 Arachidonate -- 3 -- C20:5n-3 Eicosapentaenoate Trace 11 -- C22:6n-3 Docosahexaenoate Trace 9 -- Total fatty acids 100 100 100 For each individual, all five strippings were summed. Data are expressed as percentages of total fatty acids. Not detected. DISCUSSION Kukui oil has a reputation for going rancid quickly. We chose to focus our efforts on linolenate (C18:3n-3) because it is the most unstable of the fatty acids in kukui oil. Disappearance of linolenate would be a worst-case scenario. The sensitivity of linolenate was confirmed by the fact that of the samples that did go rancid, linolenate with three double bonds disappeared far faster than linoleate with two double bonds (C 18:2n-6) or oleate with one double bond (C18: ln-9). Saturated fatty acids were stable. This said, kukui oil has an undeserved reputation for turning rancid quickly. Kukui oil is stable for three to five months, and work is in progress to stabilize it further. Brod et al. (6) noted the non-equivalence of one day at 60øC and 22 days at room temperature. We also observed this non-equivalence. In our 60øC tests, we found little if any linolenate degradation in 17 days, which is equivalent to about one year at room temperature. This was not consistent with the room temperature tests. Also, our 60øC test samples, which were approximately 90% intact based on fatty acid analyses, had very high peroxide values. This points out the problematic nature of molecular-level interpretations of peroxide value tests with kukui oil. The skin stripping method of Brod et al. (5) worked well for us. The data seemed quantitative and internally consistent. Control strippings showing the effect of diet on the skin fatty acid profile may be worth further investigation. They raise a question of whether non-clinical variations in skin fatty acid profiles affect skin properties. We began this paper by wondering why kukui oil has its reputedly excellent emollient properties. On nutritional grounds, we decided to be lukewarm about metabolic ex- planations. We are lukewarm about dry skin being caused primarily by a localized essential fatty acid deficiency in omega 6 fatty acids. This being the case, we are lukewarm about the superiority of gamma linolenate (C18:3n-6), such as found in blackcurrant oil, over the alpha form.