The chemistry behind Cosmetics

A cosmetic is defined as a preparation applied to the body, especially the face, to improve its appearance. Cosmetics play a very key role in many people's daily lives; these products are created to cleanse and modify our external appearances. Ingredients, such as water, emulsifiers, preservatives, colours and fragrances, can be both artificial and naturally occurring. Any impact that these ingredients could have on our health is dependent on the chemical compounds that they are formed from, and any dose of potentially dangerous chemicals found in cosmetics are regarded as too small to pose any risk to human health.

Cosmetics are definitely not a modern invention; Humans have been using many different types of substances to accentuate and alter features and appearances for over 10,000 years. For example, women in Ancient Egypt used to use ‘kohl’, which is a substance that contained powdered lead sulphide, to darken their eyelids. Another example is in Greece, where women used to put poisonous lead carbonate on their skin to gain a pale complexion.

Cosmetics can range from foundation to deodorant to hairspray. They tend to contain water as it plays a very important role, often acting as a solvent to dissolve other ingredients and form emulsions for consistency. However, the water must not be everyday tap water. It cannot contain microbes, toxins and any other pollutants, so only distilled, purified water is used as a base.

Here are some examples of ingredients that are used in cosmetics and how they link to chemistry:

Emulsifiers which are used in creams and lotions help to keep miscible substances from separating, for example water and oil. As many cosmetic products are based around emulsions, and since oil and water do not mix whatsoever due to hydrophobic properties, emulsifiers can be added to change the surface tension between the oil and water. This then produces a homogeneous and easily mixed product, that has an even texture. An example of an emulsifier that is commonly used in cosmetics is polysorbates, used in foundation.

Pigments, which can be used to accentuate or even alter a person’s natural colouring are also commonly used. There is a huge range of substances that are able to produce a rainbow of colours which you can see in cosmetic stores. Mineral ingredients used may include: iron oxide, manganese and chromium oxide. In addition, natural colours can be found from plants such as beet powder or from animals. Pigments can also be organic, this means they are carbon-based molecules whereas inorganic pigments tend to be metal oxides and these pigments usually are brighter and last longer than organic ones.

Fragrances play a huge role in how popular cosmetics are. Chemicals, which can be both synthetic and natural, are added to these products to achieve a more appealing and pleasant fragrance. Even products advertised as “unscented” may contain fragrances to hide any other chemical smells! Even one listing of

fragrance on a product's ingredients list may mean there could be hundreds of chemical compounds that created the final one fragrance. Esters are popularly used in fragrances due to their naturally pleasant scents. For example, Pentyl Nonoate smells like roses, and Propyl Octanoate smells like coconut. An ester is a compound that is formed from a condensation reaction that happens when there's a combination of a carboxylic acid and an alcohol. The exact combination of the type of alcohol and the type of carboxylic acid will determine which ester is produced.

Another extremely important ingredient is preservatives, as they extend cosmetics shelf life and also prevent the growth of microorganisms that could harm the user and ruin the product. Most microbes live in water, therefore, preservatives need to be water-soluble due to the water base of most cosmetic products. They can be either natural or synthetic. Some popular preservatives are benzyl alcohol, salicylic acid and formaldehyde.

Parabens are a class of chemicals that can be used as preservatives in cosmetic products(or even in food). Para Hydroxybenzoic acid (PHBA) is where the word parabens comes from, this acid is found naturally in many fruits and vegetables. The forms which parabens come in can vary, for example there is methylparaben and also isobutylparaben. They keep products bacteria and mould free. The use of parabens in cosmetics became highly discussed after a research study from the University of Reading, which reported findings that 18 out of 20 breast cancer tissue samples contained parabens. Parabens slightly mimic the actions of oestrogen, and therefore it was thought to be a problem because this hormone can enhance tumour growth. The presence of these parabens in breast tumours was presented by the media as evidence that parabens can contribute to breast cancer, which was incorrect. Currently, the use of parabens in cosmetics is considered to be safe internationally.

By Ava Barkle

References: https://www.thefactsabout.co.uk/science-behin d-cosmetics http://www.aquimicadascoisas.org/en/?episodi o=the-chemistry-of-cosmetics