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Hair relaxer

Human hair has a variety of textures, from fine to coarse, and from straight to curly. The ability to alter or change the texture of hair through chemical processes is important both for men and women, and hair care products and chemical processes that can alter the texture of hair are in great demand. For example, individuals with excessively curly hair seek products that can straighten or "relax" hair. In today's market, there is an increasing demand for hair care products referred to as "hair relaxers" which can relax or straighten naturally curly or kinky hair. Hair relaxers may either be applied in a hair salon by a professional or in the home by the individual consumer. The hair fiber consists of the cuticle, cortex, and medulla. The cuticle surrounds the actual fiber and consists of overlapping flat scale-like cells. The cuticle protects the hair fiber and is generally more resistant to penetration and attack by chemical agents. The cortex consists of spindle shaped cells which are oriented along the axis of the hair fiber. Microfibrils of the protein keratin are found in cortical cells. The medulla runs down the center of the hair fiber and usually consists of hollow cells. Straightening or relaxing the hair fiber involves breaking the disulfide bonds found in the hair fiber proteins and reorienting them so that the hair fiber forms the desired "straight" configuration. The relaxing process operates by changing the chemical structure of hair fibers. Hair fibers are comprised of keratin, which is in turn comprised of polypeptide chains bonded together by three types of bonds: cystine bonds, hydrogen bonds and salt linkages. The relaxing process operates primarily on the cystine bonds. When the cystine bonds are exposed to an alkaline relaxing solution, they are transformed to lanthionine bonds. The chemical term for the hair relaxation process is lanthionization. Hair relaxers are generally supplied as "with base" or "no-base" formulations. A "with base" formulation is generally supplied in two packages; one containing the oleaginous base and one containing a thickened aqueous composition of alkaline materials. No-base formulations are one package systems in which the aqueous and oleaginous materials are co-emulsified. The no-base formulations are applied directly to the user's hair without a prior pretreatment of the scalp.

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