j. Cosmet. Sci., 50, 327-339 (November/December 1999) Effect of coconut oil on prevention of hair damage. Part I AARTI S. RELE and R. B. MOHILE, Research & Development Department, Nature Care Division, Marico Industries Ltd., Andheri, Mumbai 400 058, India Accepted for publication September 30, 1999. Synopsis Beneficial effects of coconut oil on prevention of combing damage on different types of hair have been established by protein loss and water retention measurements. In vivo, salon-based, half-head tests confirm these beneficial effects. Beneficial effects were also observed on chemically (bleached) and thermally (treated with boiling water) damaged hair. In addition to providing lubricating film, it is hypothesized that coconut oil used as a prewash penetrates endocuticular material in the intercuticular region and reduces its swelling propensity. The penetration of water into the intercuticular region is prevented by hydrophobic oil film at the edge of the cuticle. Both these effects prevent the lifting of the surface cuticle and its breaking by the force exerted by the comb. INTRODUCTION Hair fibers consist of three distinct morphological components, namely, the cuticle, the cortex, and the medulla. Layers of cuticle cells form the outer sheath of the fiber and are mainly responsible for the cosmetic properties of hair. Mechanical properties, on the other hand, are attributed to the cortex, which forms the bulk of the fiber. Because of extensive cross-linking, cuticle cells tend to be brittle and, therefore, are susceptible to damage by grooming procedures, especially wet combing (1). The loss of cuticle cells by gradual chipping impairs the structural integrity of hair, leading ulti- mately to split ends and fracture. This limits the length and the cosmetic qualities of hair such as smoothness and shine. Grooming methods involving abrasive procedures are known to damage hair and its appearance. Historically, coconut oil has been used as a hair dressing in the developing countries in the tropical regions of the globe where coconut is cultivated extensively. Prolonged use of coconut oil has been known to lead to healthy-looking long hair, suggesting that it may prevent damage to the cuticle in grooming procedures involving abrasion. Obvious is the lubricating effect of oil on fiber friction, which reduces abrasive damage, especially in combing. This investigation is aimed at presenting alternative mechanisms for the beneficial effect of coconut oil in preventing hair damage when used as a preconditioner. Although 327

328 JOURNAL OF COSMETIC SCIENCE several methods involving scanning electron microscopy (SEM) and measurement of combing forces and tensile mechanical properties have been used earlier to characterize hair damage, we have used protein loss and water uptake methods for this purpose (3). We have also used consumer-perceived attributes of hair quality as additional measures of hair damage and its alleviation. Furthermore, these methods have been extended to study the beneficial effects of coconut oil on chemically treated (bleached) hair and hair treated with boiling water for 2 hr. There is a large amount of work showing this effect. It is well known that bleached hair, because of its high degree of swelling, is more prone to grooming damage, especially in the wet condition (2). MATERIALS AND METHODS MATERIALS Samples of straight, curly, and wavy hair of Indian origin were used in this work along with a sample of untreated dark brown hair from DeMeo Brothers, New York. The lengths of the Indian and DeMeo hair strands were 25 and 15 cm, respectively. The reagents for protein estimation were obtained from Sigma Chemicals Co. (St. Louis, MO). All other reagents were of analytical grade. Sample Preparation. Hair tresses of 3 + 0.5 g (or 2 + 0.2 g for DeMeo hair) were prepared for this investigation. They were cleaned by soaking in 0.01% (w/v) of polysorbate 80 (30 rain at 28øC), de-ionized water at room temperature (several rinses), and 0.01% (w/v) acetic acid (15 rain at 28øC), in that order. Finally, they were extensively rinsed in water and blow-dried. Bleached hair was prepared by using a bleaching kit containing 30 vol. hydrogen peroxide and ammonia solution to adjust the pH to -10. Five milliliters of this solution was employed per tress, and the treatment time was 120 min. With this treatment the tresses became light brown with a red tone. The boiling water treatment was carried out for 120 min. After bleaching or boiling in water, some of the tresses were treated with 0.2 ml of coconut oil, spread uniformly throughout the tress by a brush. The tresses were stored at room temperature for 48 hr before use. The entire study involved samples with the following treatments on four types of hair, i.e., DeMeo and Indian (straight, curly, and wavy): (a) undamaged control (b) undam- aged/coconut oil (c) bleached (d) coconut oil/bleached* (e) bleached/coconut oil* (f) boiling water (g) coconut oil/boiling water* and (h) boiling water/coconut oil*. Twenty-five replicate tresses were used for each treatment. METHODS The tresses were wet under running tap water (28øC) and were washed with a 20% Sequential treatments.