Advances in scientific characterization techniques have enabled us to obtain unprecedented levels of information about nanoscale materials due to the ability to both directly and indirectly observe these materials in situ (in their natural environment). Fortunately for us in the curly world, one complex biological system that has received study is human hair. Through use of new methods, scientists have been able to identify and study the role of the multitudes of subspecies and structures present in hair. This has provided us with new insight regarding the cuticle-cuticle cell membrane complex (CCMC), and its major lipid component, 18-methyl eicosanoic acid (18-MEA). We have found that this relatively small fatty acid plays a very important role in the health and beauty of our hair, and it is becoming a bit of a buzzword in the industry. What exactly is 18-MEA, and how does it make such an important contribution? Perhaps more importantly, how can we protect the 18-MEA levels in our hair or replenish it if we have depleted it?
Cuticle glue and cushion
The protective cuticle layer that encapsulates the outer portion of each hair strand is a highly complex biocomposite structure made up of multiple layers of overlapping protein scales. Between each layer of scales, there exists a region called the cuticle-cuticle cell membrane complex, which is comprised of several layers of both delta and beta protein structures, a significant amount of 18-MEA covalently bonded to the b-protein structure, and a small amount of unbound lipids such as oleic and palmitic acid. This entire structure acts as a protective cushion and cement between the cuticle scale layers.
The covalently-bonded 18-MEA is responsible for providing hair with its hydrophobicity (water-repellent property), which protects hair by preventing it from absorbing too much water from the environment. It also provides hair with softness, lubricity, and shine. More significantly, an intact layer of 18-MEA acts to decrease tangling in wet hair and in the transition from wet to dry, by encouraging adjacent hair strands to lie neatly in parallel to one another, smoothly aligned. It does this due to its ability to decrease surface friction by changing the receding contact angle of water. When hair is lacking 18-MEA, the strands become entangled and stuck to one another, and the hair dries more quickly in these tangled packets, resulting in greater tangling when hair is dry.