Hair is a filamentous protein that grows from follicles in the dermis of your skin. It is primarily made of dead, keratinized cells. Contact Hairicc now!
It serves many functions, including protection from sunlight and heat regulation. It also plays a role in personal aesthetics and social identity. Your hair is unique to you, just like your fingerprints and DNA.
Hair is primarily composed of the protein keratin, which is also found in fingernails, toenails, and the horns of cows, rhinoceri, and sheep (but not antlers). It’s a fibrous, helix-shaped protein that provides strength and resilience to the hair. It’s also insoluble in water and helps to protect the internal structures of the strands from external damage.
It’s also used in various hair treatments for strengthening, shine and hydration. It can help to reduce damage and even repair broken areas of the hair by filling in gaps within the cuticle layer, and it keeps the strands hydrated by limiting water loss from the cuticles.
To determine if a product has proteins in it, check the ingredients list. Look for the words hydrolyzed, amino acids or peptides in the ingredient list to identify proteins in the formula. These are smaller proteins that can penetrate the hair and bind to the strands, helping them retain moisture. They’re often used in products that require regular use, like a deep conditioner or hair mask.
If the product has a label that indicates it’s a “Protein Treatment,” the protein levels are typically much higher than those in general hair products, such as shampoo, everyday conditioner or leave-in conditioner. These are usually listed towards the end of the ingredient list and tend to be less concentrated than the specialized protein treatments.
Keratin
Keratin is a fibrous protein that gives structure to the hair and nails. It is also present in the outermost layer of the skin and the cornea of the eye. All keratin proteins have a unique tripartite structure consisting of three parts: the head domain towards the N-terminal end, the rod domain in the middle and the tail domain at the C-terminal end (Fig. 2a). Keratin proteins are able to form heterodimers, tetramers and eventually keratin filaments on their own. In order to do this, each protein contains a specific amino acid sequence at the N-terminal end of the head domain that is able to initiate and stabilize the formation of an a-helix in the rod domain. This is called the helix-initiating motif. It is also known that the a-helix of the rod domain has a negative charge, which helps in the binding and assembly of keratins to polarized structures within cells.
The a-spiral domain of the rod domain is stabilized by interchain ion pairings, hydrogen bonds and disulfide bridges between the helixes. The a-helix is surrounded by a tetramer of non-helical head domains, which are responsible for the elastic properties of keratins.
Different keratins are expressed in different parts of the body, depending on the specific cell type and its keratinizing functions. The basic keratin K32, which has a MW of 50.3 kDa and an isoelectric pH of 4.5, is expressed in the base and middle of the hair cuticle (Langbein et al. 2001). It can form heterodimers with the acidic keratins K82 or K85. It is also expressed in the keratinizing epithelial cells of the companion layer of the inner root sheath of the hair follicles (Szeverenyi et al. 2008).
Other keratins, like the acidic keratins K9 and K17, are produced in the keratinizing epithelial of the nail plate and scalp. In addition, the basic keratin K6 is also expressed in the keratinizing cells of the nail plates and scalp as well as in the companion cells of the inner root sheath of the follicles. A new variant of this basic keratin, the K75 or K6hf, has been identified in the cells forming the companion layer of the inner root sheath and is also found in the scalp hairs (Winter et al. 1998).
Fatty Acids
Lipids (fats) are a key part of the hair fibre and provide elasticity, waterproofing and resistance to bending, twisting and elongation. They can be found in the medulla and cuticle, with most of them being free fatty acids (FFA) such as palmitic and stearic acids. Other lipids in the hair are cholesterol, triglycerides and wax esters. Fatty acid-derived lipids are also used as emulsifying agents and stabilizers in personal care products.
Fatty acids are an important structural component of cell membranes and also function as energy sources and signalling molecules. They can be synthesised by the body, ingested as food or applied topically in a variety of ways. Some fatty acids are known to have beneficial properties in particular for the skin and hair such as enhancing skin suppleness, reducing inflammation, providing UV protection and acting as anti-ageing agents.
The lipids in the hair can be classified as exogenous or endogenous depending on whether they are derived from sebum, or from hair matrix cells. Exogenous lipids include free fatty acids (FFA), triglycerides, cholesterol, wax esters and squalene (SQ). The lipid composition varies between hair fibres. Endogenous capillary lipids consist of FFA, CH, ceramides (CER), glucosyl ceramides and 18-methyleicosanoic acid (18-MEA) which is covalently bound to the hair cuticle surface via a thioester bond.
It has been shown that lipids can be depleted by frequent washing and other cosmetic treatments, for example colouring or perming. Lipids are also lost during daily weathering and during contact with water. Lipids can be replenished by combining fatty alcohols, such as cetyl and stearyl alcohols, with anionic surfactants to form gel networks that efficiently penetrate into the hair. The effect of the length of fatty alcohol chain on penetration was examined and the results showed that long chains penetrated better than short ones. This was due to the larger polarity and volume of these substances which increased their ability to cross the hair cuticle.
Styling
Hair styling is the practice of arranging hair into specific shapes and designs for aesthetic reasons. Hairstyles are influenced by practical, cultural or social considerations, and they can be altered with the use of a comb, brush, hair pins, rollers, blow dryers and other tools. The term hairdressing is also used to describe the process of preparing the hair for styling and may include cutting, dyeing, extensions, perms and other processes.
Styling products such as leave-in conditioners, detanglers, clays, gels, mousses and hair tonic are often used in salons and homes to change the texture or shape of the hair. Applied properly, these products usually do not damage the hair except by drying it out. However, many styling products contain alcohols that can dissolve oils and cause build-up, resulting in dull hair.
Styling techniques include spritzing the hair with saltwater to create a beachy look, backcombing to add volume and a technique known as French braiding that starts at the nape of the neck. These techniques can cause tangles and damage if not used correctly.