240 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS lipid" at 5% of total caloric intake brought his triene:tetraene ratio into normal range in one week. This case contrasted topical application of EFAs with infusion of small amounts of EFAs. With an average intake of Americans at 30% kcal from fat, EFAD is not something one would expect to see in Americans except under very unusual circumstances. In this work we exclude the possibility that kukui oil's superior skin feel is due to its penetrating ability. We demonstrate that coconut oil, a saturated fat, penetrates the skin as well as kukui oil. Thus we will be left with the hypothesis that kukui oil forms a semipermeable barrier that protects dry skin from further damage and permits dry skin to heal naturally. While the definition of dry skin is beyond the scope of this paper, it may be assumed that dry skin is characterized by apparent dryness, scaling, cracking, etc. These con- ditions may be induced by the loss of natural lipids in the stratum corneum. Such could occur by swabbing with acetone (3). This treatment decreases the barrier function of the skin, as may be seen by the increase in transepidermal water loss (TEWL). There is a linear relationship between lipid removal and the increase in TEWL. It follows that use of household chemicals such as soaps, or extreme exposure to the wind, sun, and sea such as occurs commonly in Hawaii, may also cause dry skin. The same condition is often reported by people who live in very cold environments (where barrier lipid fluidity may be inappropriate to prevent TEWL) or very dry environments (where TEWL would be extremely high). We also note that dry skin heals naturally. Unless further damage occurs, barrier function is restored to dry skin within 48 hours (3). Intervention in the healing process is not straightforward. On the one hand, some TEWL must occur because no lipid biosynthesis or recovery of the normal rate of TEWL occurs if the skin is protected occlusively with films such as latex. On the other hand, unprotected skin may be damaged further. We propose that lipids composed of a mixture of saturated and unsaturated fatty acids could provide a protective barrier against excessive TEWL and yet promote healing. Perhaps this explains the emollient properties of kukui oil. Kukui oil contains 8.1% saturated fatty acids, 15.3% monounsaturated fatty acids, 43% linoleate (C18:2n-6, a diunsaturated fatty acid), and 33% linolenate (C18:3n-3, a triunsaturated fatty acid). Another purpose of the present study is to determine the stability of kukui oil. Kukui oil has the reputation of being highly susceptible to rancidity. It normally leaves the factory with a peroxide value of 2. Sometimes batches are rejected because peroxide values have risen to 10 or more. METHODS SAMPLES Coconut oil was purchased commercially. Kukui oil samples with and without antiox- idants were obtained from the production line of the Hawaiian Kukui Nut Company. Kukui lotion was obtained similarly. It contained water, 10% kukui oil, 3% macadamia nut oil, and an unextraordinary mixture of buffers and emulsifying agents.

EMOLLIENT ACTION OF KUKUI NUT OIL 241 FATTY ACID ANALYSIS Lipid saponification, methylation, and gas chromatographic quantification of fatty acid methyl esters were done as described previously (4), except for skin stripping samples, which were concentrated with a nitrogen stream just before running on the gas chro- matograph. AOAC methods were used to determine peroxide values. STABILITY In room temperature stability studies, kukui oil was held in glass vials on the windowsill (approx. 28øC). Some samples were flushed with nitrogen and sealed, and others were left open to the atmosphere with glass wool plugs keeping debris out of the vials. Some samples contained antioxidants (a mixture of vitamins C, E, and A), and others did not. In these stability studies, each data point represents an average of triplicate analyses. Accelerated rancidity tests were done with samples held in vials in a dry incubator at 60øC on the laboratory bench. SKIN PENETRATION Skin strippings were done following the approach of Brod et al. (5). Samples (none, 20 Ixl coconut oil, 20 •1 kukui oil, or 50 mg of kukui lotion) were applied to 25-cm 2 sections of skin on the shins of test subjects. Samples were rubbed into the skin gently with a test tube. After one and a half hours, Blenderm © tapes were applied to each of the sections with a light touch and removed after about one minute. A total of five consecutive strippings were done for each sample. No measurements were taken of the depths of skin removed with each stripping. However, we were conscious of possible inconsistency and attempted to remove equal amounts of skin in each stripping. There were no apparent differences in stripped skin to which different treatments were applied. In no case did the skin seem "tender" or "raw," as was the case in a preliminary study when tapes were applied vigorously. Oils were extracted from individual tapes with hexane as described by Brod et al. (5) and were analyzed for fatty acids as described above. A follow-up test was done at half- loading rates (10 •1 coconut oil and 10 •1 kukui oil per 25-cm 2 section of skin). STATISTICS The Student's t-test was used. RESULTS STABILITY The linolenate levels in kukui oil were taken as indicative of rancidity because linolenate is the most unstable fatty acid in kukui oil. Figure 1 is a room-temperature stability test. The closed triangles represent a control reaction with kukui oil containing no antioxidants and exposed to air. The data show that kukui oil rapidly became rancid