EFFECT OF COCONUT OIL ON HAIR DAMAGE 187 60-( i• 52 3 •[• 52 4 • 52 3 J ß ' 0.4 'i' '50.9 "", 45 .{ .?• . RETENTION 30 { • ß INDEX • '• COCONUT SUNFLOWER COCONUT SUNFLOWER OIL OIL OIL OIL PRE-WASH TYPES OF OILS POST-WASH BWITHOUT E3WITH J Figure 7. Comparison of water retention index for bleached hair. coconut oil and mineral oil is probably due to the difference in their ability to penetrate the hair (4). The smaller effect of sunflower oil may be due to the presence of unsat- uration in the molecule. No information regarding the penetrability of sunflower oil in the hair is available. The same effect was seen in the half-head test in a salon trial, as seen in Figure 5. The effect of various oils in preventing cuticle damage in laboratory tests was established statistically by a parametric test, t-test. The outcome of the analysis is shown in Table III. The t-values clearly indicate that damaged as well as undamaged hair benefits from application of coconut oil as a pre-wash conditioner, whereas in the case of sunflower oil and mineral oil, there was no effect. The effects of coconut oil were also positive in a salon test. In both normal and bleached hair, treatment effects in reducing protein loss were significant, whereas the same findings were absent in the case of mineral oil and sunflower oil. The values of t for coconut oil are statistically significant, whereas for mineral oil and sunflower oil, they are not. See Tables IV and V for ANOVA data for treatment effects for protein loss and water retention index.

188 JOURNAL OF COSMETIC SCIENCE 24.2 % WATER RETENTION INDEX 10- COCONUT SUNFLOWER COCONUT SUNFLOWER OIL OIL OIL OIL PRE-WASH TYPES OF OILS POST-WASH •WITHOUT EIWITH Figure 8. Comparison of water retention index for hair treated with boiling water. WATER RETENTION INDEX The water retention index for undamaged hair is shown in Figure 6. From the data it can be seen that coconut oil reduces the WRI of undamaged hair by 44%, whereas in the case of mineral oil and sunflower oil, there is hardly any reduction in WRI, as seen in Figure 6. The ability of coconut oil to penetrate hair (4) supports this observation. The data for the bleached, heat-damaged, and UV-damaged hair are shown in Figures 7-9, respectively. For these damaged samples, the WRI is much higher than that for the undamaged hair. This is mostly due to the chemical degradation of proteins, generating hydrophilic groups. Both the cleavage and oxidation of disulfide bonds, followed by their oxidation to cysteic acid, as well as hydrolysis of the peptide linkage, occur, although the contribution of the latter is probably minor. All samples show a reduction in the WRI as a result of the application of coconut oil, whereas the same findings were not observed to a significant level in the case of mineral oil and sunflower oil. Assuming that most of the water is absorbed by the fiber, the WRI reflects the swelling propensity