J. Cosmet. Sci., 63, 27–31 (January/February 2012) 27 Quantitative measurement of the penetration of coconut oil into human hair using radiolabeled coconut oil V. GODE, N. BHALLA, V. SHIRHATTI, S. MHASKAR, and Y. KAMATH, Marico Research Centre, Marico Ltd., Mumbai, India (V.G., N.B., V.S., S.M.), and Kamath Consulting Inc., 11 Deer Park Drive, Monmouth Junction, NJ 08852 (Y.K.). Accepted for publication June 9, 2011. INTRODUCTION Applying oil to hair and skin is an age-old tradition in Asian and African countries. The traditional system of medicine in India, Ayurveda, has several formulations of oils (based mainly on coconut and sesame) with herbal extracts. These oils are supposed to benefi t both hair and the hair follicle. Generally, these oils are applied as prewash hair dressings. This is also true of plain oils without any herbal actives. In either case, the hydrophobicity of the oil plays an important role in protecting hair from damage. Surface lubrication is the fi rst level of defense against abrasive damage in grooming. A more signifi cant factor is the protec- tion of hair and especially the hair follicle from surfactant damage. Low-molecular-weight surfactants such as sodium lauryl sulfate (SLS) in shampoos can penetrate easily into the structure of hair and interfere with the formation of secondary valence bonds such as hydro- gen bonds and salt linkages. This can weaken hair. On the positive side, penetrated oil can reduce the amount of water absorbed in the hair, leading to a lowering of swelling. This can result in lower hygral fatigue (repeated swelling and deswelling), a factor which can damage hair. The softening effect of moisture is replaced by the plasticizing effect of oil. As far as the follicle is concerned, the oil can fi ll the gap between the hair and the follicle wall and prevent the penetration of the surfactant solution into the follicle. Surfactant molecules like SLS, when penetrated into the follicle, can interfere with the adhesion of follicular structures, leading to loosening of hair in the follicular cavity, ultimately leading to hair loss. Applying oil on a regular basis can eliminate follicular damage leading to hair loss. The overall effect is a head full of rich and long hair. The fi rst attempt to show the penetration of hair by coconut oil (CNO) was made by Ruetsch, Kamath, et al. (1). The method used was time-of-fl ight secondary ion mass spec- trometry (TOF-SIMS), which was able to map the molecules of CNO in the cross section of hair treated with CNO. Although the method could show the depth of penetration, it was incapable of yielding quantitative (how much) data. Since then, the TOF-SIMS method has been used by Hornby et al. (2) to study the penetration of other vegetable oils.