j, Cosmet. Sci., 54, 175-192 (March/April 2003) Effect of mineral oil, sunflower oil, and coconut oil on prevention of hair damage AARTI S. RELE and R. B. MOHILE, Research and Development Department, Nature Care Division, Marico Industries Ltd., MumbaL India. Accepted for publication April 29, 2002, Synopsis Previously published results showed that both in vitro and in vivo coconut oil (CNO) treatments prevented combing damage of various hair types. Using the same methodology, an attempt was made to study the properties of mineral oil and sunflower oil on hair. Mineral oil (MO) was selected because it is extensively used in hair oil formulations in India, because it is non-greasy in nature, and because it is cheaper than vegetable oils like coconut and sunflower oils. The study was extended to sunflower oil (SFO) because it is the second most utilized base oil in the hair oil industry on account of its non-freezing property and its odorlessness at ambient temperature. As the aim was to cover different treatments, and the effect of these treatments on various hair types using the above oils, the number of experiments to be conducted was a very high number and a technique termed as the Taguchi Design of Experimentation was used. The findings clearly indicate the strong impact that coconut oil application has to hair as compared to application of both sunflower and mineral oils. Among three oils, coconut oil was the only oil found to reduce the protein loss remarkably for both undamaged and damaged hair when used as a pre-wash and post-wash grooming product. Both sunflower and mineral oils do not help at all in reducing the protein loss from hair. This difference in results could arise from the composition of each of these oils. Coconut oil, being a triglyceride of lauric acid (principal fatty acid), has a high affinity for hair proteins and, because of its low molecular weight and straight linear chain, is able to penetrate inside the hair shaft. Mineral oil, being a hydrocarbon, has no affinity for proteins and therefore is not able to penetrate and yield better results. In the case of sunflower oil, although it is a triglyceride of linoleic acid, because of its bulky structure due to the presence of double bonds, it does not penetrate the fiber, consequently resulting in no favorable impact on protein loss. INTRODUCTION Morphologically, a fully formed hair fiber contains three and sometimes four different units or structures. At its surface, hair contains a thick protective covering consisting of layers of fiat overlapping scale-like structures called the cuticle. The cuticle scales surround the cortex, which contains a major part of the fiber mass. The cortex, the second unit, consists of spindle-shaped cells that are aligned along the fiber axis. Cortical cells contain the fibrous proteins of hair. Thicker hairs often contain one or more loosely packed porous regions called the medulla, located near the center of the fiber. The fourth 175

176 JOURNAL OF COSMETIC SCIENCE unit is the intercellular cement that glues or binds the cells together, forming the major pathway for diffusion into the fibers. The cuticle consists of flat overlapping cells (scales). The cuticle cells are attached at the proximal end (root end), and they point toward the distal end (tip end) of the hair fiber. However, cuticle damage evidenced by broken scale edges that can usually be observed several centimeters away from the scalp is caused by weathering and mechanical damage from the effects of normal grooming actions, such as combing, brushing, and shampoo- ing. Because of extensive cross-linking, cuticle cells tend to be brittle and, therefore, are susceptible to damage by grooming procedures, especially wet combing (1). In long hair fibers (25 cm or longer), progressive surface damage may be observed. The loss of cuticle cells by gradual chipping impairs the structural integrity of hair, leading ultimately to split ends and fracture. This limits the length and the cosmetic qualities of hair such as Table I Design of Experiment Using the Taguchi Model No. Oils Hair type Hair treatment Oiling sequence Shampooing 1 CNO Straight Undamaged Before Once 2 SFO Curly Undamaged Before Once 3 MO Wavy Undamaged Before Twice 4 MO Permed Undamaged Before Twice 5 CNO Straight Bleached Before Once 6 SFO Curly Bleached Before Once 7 MO Wavy Bleached Before Twice 8 MO Permed Bleached Before Twice 9 SFO Straight Boiled Before Twice 10 CNO Curly Boiled Before Twice 11 MO Wavy Boiled Before Once 12 MO Permed Boiled Before Once 13 SFO Straight UV-treated Before Twice 14 CNO Curly UV-treated Before Twice 15 MO Wavy UV-treated Before Once 16 MO Permed UV-treated Before Once 17 MO Straight Undamaged After Once 18 MO Curly Undamaged After Once 19 CNO Wavy Undamaged After Twice 20 SFO Permed Undamaged Afier Twice 21 MO Straight Bleached After Once 22 MO Curly Bleached After Once 23 CNO Wavy Bleached After Twice 24 SFO Permed Bleached After Twice 25 MO Straight Boiled After Twice 26 MO Curly Boiled After Twice 27 SFO Wavy Boiled Afier Once 28 CNO Permed Boiled After Once 29 MO Straight UV-treated After Twice 30 MO Curly UV-treated After Twice 31 SFO Wavy UV-treated After Once 32 CNO Permed UV-treated After Once Treatments were sequential. If the treatment is designated as CNO-Permed-Boiled-After-Once, it means permed hair was first put in boiling water for 120 min and air dried, and then 0.2 ml of CNO was applied to it. This treatment was carried out for all 25 hair tress samples. Twenty-five replicate tresses were used for each treatment.