Hair Cosmetics
Hair Cosmeticsby Jasmine Chan
INTRODUCTION TO HAIR COSMETICS
Hair plays an important role in people’s everyday lives as it can shape towards your liking. Whether if your hair is long or short, straight or curly, colourful or single-coloured, our hair is one of the first distinctive features during first impressions.
Hair cosmetics are any substances or mixtures intended to be used for the hair, mainly to clean it, keep it in good condition or to change its appearance. [1] Hair cosmetics can be split into two categories: temporary and permanent. Temporary hair cosmetics include shampoos and conditioners, whereas permanent hair cosmetics include hair bleaching agents, permanent hair dyes, permanent hair waves and permanent hair straightening. [2]
SHAMPOOS
Fig.1 Examples of Shampoos.
“Shampoos So Good You'll Forget They're Natural.” Harper's BAZAAR, 22 Apr. 2020, www.harpersbazaar.com/beauty/hair/g8776/organic-natural-shampoo/.
Shampoos are vital household items, prescribed to treat the hair and scalp by massaging the product in with wet hair. It consists of 10-30 ingredients, including surfactants that remove sebum and preservatives to inhibit bacterial and microorganism growth. Shampoos are alkaline substances which work by mildly removing the majority of the dirt and sebum from hair shafts and scalp. Shampoos must not remove all of the dirt and sebums as natural oils and sebum on the skin are important to act as a barrier to prevent damage. They are typically in a form of a viscous liquid but in rare cases, they can be found as a bar form. [2]
Surfactants in shampoos are vital as the substance intended for cleaning. Hair must be cleansed as most dirt are not soluble with only water. Shampoo surfactants are negatively charged where one end is soluble in water and the other end is soluble in oils. [3] They surround grease found on the hair and scalp and the end that is soluble in oil would go towards the grease and cleanse those areas through emulsification. Since they are negatively charged, and the surface of the hair shaft is also negative, this causes the surfactant molecules and the hair shaft to repulse which forces them to be apart with one another. This decreases the tension between water and grease on the hair and scalp and ensures that dirt cannot be re-deposited on those areas. [2] After shampooing, the scalp becomes free of dirt which allows new sebum to be regenerated. This helps to maintain hygiene and reduce the probability of scalp irritation and inflammation. [3]
Shampoos often contain chemicals to prevent a common scalp disorder known as dandruff. Dandruff is products resulted from an inflammatory reaction, associated with a fungus called Malassezia. This fungus metabolises triglycerides in hair sebum which causes an unsaturated lipid to be formed. This lipid byproduct then penetrates the top layer of the epidermis on the scalp which causes the inflammatory reaction to occur. [3]
CONDITIONERS
“Herbal Essences' Coconut Milk Conditioner Works Wonders on Dry Hair.” Good Housekeeping, 6 Aug. 2020, www.goodhousekeeping.com/beauty-products/g26212823/best-conditioner-for-dry-hair/.
Most likely after shampoo, consumers would use conditioners as the next step. Despite most shampoos containing conditioning agents to smoothen the hair, conditioner is able to further minimise hair frizzing, making the hair more manageable and shiny. Conditioners are acidic substances which are able to reduce chemical damage of the hair from permanent hair cosmetics.
Conditioners also have a large percentage composed of surfactants. Comparing the surfactants between shampoo and conditioners, conditioner surfactants are positively charged whereas shampoo conditioners are negatively charged. As the hair shaft is negative, the positive charge of the surfactants in conditioners helps to neutralise the negative charge to reduce static electricity in the hair.
Conditioners are also used to help cuticles that are raised to lie down against the hair surface to enhance the smoothness of the hair. Silicones such as dimethicone are widely common in conditioners to protect the hair shaft from severe damage. They also contain a wide variety of polymers to fill hair shaft defects to further increase the smoothness and shine of the hair.
“Hair Care Cosmetics.” Cosmetic Science and Technology: Theoretical Principles and Applications, by J. Yang, 2017, pp. 601–615.
HAIR BLEACHING AGENTS
Bleaching agents permanently lighten the hair without colourants. The most common ingredient in bleach is hydrogen peroxide, an alkaline which opens the hair shaft and reacts with melanin by penetrating into the cortex of the hair, causing an oxidation reaction. [4] Hydrogen peroxide breaks double bonds in eumelanins and phaeomelanins by removing electrons. This causes pigments to be shorter, causing the pigments to absorb shorter wavelengths of light which therefore makes the hair it seem lighter in colour. [5] Bleached hair is not completely colourless, it causes the hair to have a pale yellow tint since the keratin in the hair has a natural straw-yellow colour. Bleach reacts more readily with eumelanins compared to phaeomelanins. With people who have red-heads, reddish colour may still remain after the bleaching process. [4]
PERMANENT HAIR DYES
Permanent hair dyes change the colour of the hair permanently via oxidation reactions which allow coloured molecules to penetrate into the hair. Permanent hair dyes are resistant to any external factors, including shampoos and conditioners. [3]
The first permanent hair dye is a chemical known as PPD (paraphenylenediamine) which produces brown shades. Permanent hair dyes must consist of primary intermediates in order for the oxidation reaction to occur. Primary intermediates only produce molecules of dye when exposed to an oxidising agent. Hence, all hair dyes consist of various levels of hydrogen peroxide, depending on the desired lightness in colour to simultaneously remove the colour of the hair as well as to introduce the new desired colour. [5] In addition to what has been mentioned about hydrogen peroxide, it also oxidises the primary intermediate which produces a reactive product. This product then undergoes another reaction to form the dye molecules.
If a brown colour is not the desired resulting colour, other compounds can be added into the hair dye mixture to form a variety of other colours. These compounds are coupling agents which react with primary intermediates to produce a range of coloured dyes. Hair dyes usually contain a range of a few different coupling agents in varying concentrations to achieve the exact colour wanted.
The permanent hair dying process carried out in an alkaline environment by including ammonia in the hair dye mixture. The ammonia causes the cuticles to swell, which allows the dye to enter the hair and causes the colour to be permanent. [6] This opens the hair shaft, which allows the dye to be deposited into the hair. These dye molecules mimic the natural melanin pigments which allow it to permanently stay in the hair. After dyeing the hair, an acidic conditioner is used to close the cuticle. [7]
PERMANENT HAIR WAVES
Permanent hair waves are caused by a chemical which breaks the strong disulphide bonds in the hair shaft. Keratin in hair is made of alpha-helices which consists of high concentrations of cysteine. There are strong disulphide bonds between the sulphur of cysteine which prevents the keratin molecules from slipping past one another. [8]
An alkaline substance, commonly ammonium thioglycolate, reaches inside the cortex and breaks the strong disulphide bonds in the hair shaft. This causes the alpha-helices to able to move and changes to a new position. The hair is then placed on a curler, and an oxidising agent such as diluted hydrogen peroxide is applied. The oxidising agent is able to reform the disulphide bonds in the new shifted position, causing permanent hair waves. [9]
PERMANENT HAIR STRAIGHTENING
Similarly to permanent hair waves, permanent hair straightening can be achieved by targeting those disulphide bonds. Instead of placing the hair on a curler after applying the alkaline solution, the hair is combed straight and is held that that position. An acidic solution is then added which neutralises the bonds to stay in their new position. [10]
CONCLUSION
Hair cosmetics are crucial to our daily lives. Personally, I love to experiment with new styles with my hair, usually with permanent hair dyes to introduce change. Without them, we would lack basic personal hygiene. Additionally, we would not have so many options to vary and change our hair!
BIBLIOGRAPHY
[1] “Definition of a Cosmetic.” Hair and Makeup Artist Handbook, 1 June 2020, hair-and-makeup-artist.com/definition-of-cosmetic/.
[2] Alessandrini, Aurora, and Bianca Maria Piraccini. “Essential of Hair Care Cosmetics.” MDPI, Multidisciplinary Digital Publishing Institute, 27 Sept. 2016, www.mdpi.com/2079-9284/3/4/34.
[3] “Hair Care Cosmetics.” Cosmetic Science and Technology: Theoretical Principles and Applications, by J. Yang, 2017, pp. 601–615.
[4] Helmenstine, Anne Marie. “The Science Behind How Hair Coloring Works.” ThoughtCo, www.thoughtco.com/salon-hair-color-chemistry-602183.
[5] “Hair Bleach.” Science Behind Hair Dye And Bleach, sciencebehindhairdye.weebly.com/hair-bleach.html.
[6] “The Chemistry of Permanent Hair Dyes.” Compound Interest, 16 Mar. 2018, www.compoundchem.com/2015/05/14/hair-dyes/.
[7] “How Do Different Types of Hair Dye Work?” Lab Muffin Beauty Science, 21 Apr. 2019, labmuffin.com/how-does-hair-dye-work/.
[8] “The Chemistry of Perming & Rebonding.” Https://Is.muni.cz/El/Sci/podzim2013/C3804/The_chemistry_of_perming___rebonding.Pdf?Info=.
[9] “Permanent Hair Wave.” Chemistry LibreTexts, Libretexts, 11 Aug. 2020, chem.libretexts.org/Bookshelves/Biological_Chemistry/Supplemental_Modules_(Biological_Chemistry)/Proteins/Case_Studies:_Proteins/Permanent_Hair_Wave.
[10] “The Chemistry of Hair Straightening.” Theory, hairstraighteningexperiment.weebly.com/theory.html.
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