The chemistry of cosmetics
The chemistry of cosmetics
Cosmetics materials are not a modern invention. Humans have used various substances to alter their appearance or accentuate their features for at least 10,000 years, and possibly a lot longer.
Women in Ancient Egypt used kohl, a substance containing powdered galena (lead sulphide—PbS) to darken their eyelids, and Cleopatra is said to have bathed in milk to whiten and soften her skin. By 3000 B.C men and women in China had begun to stain their fingernails with colours according to their social class, while Greek women used poisonous lead carbonate (PbCO3) to achieve a pale complexion. Clays were ground into pastes for cosmetic use in traditional African societies and indigenous Australians still use a wide range of crushed rocks and minerals to create body paint for ceremonies and initiations.
Today, cosmetics are big business. According to the 2011 Household Expenditure Survey, conducted every five years by the Australian Bureau of Statistics, Australians spend around $4.5 billion on toiletries and cosmetic products every year. Cosmetic advertising, previously directed mainly at women, is now targeting a wider audience than ever.
What is a cosmetic?
In Australia, a cosmetic is defined under the Industrial Chemical (Notification and Assessment) Act 1989 as ‘a substance or preparation intended for placement in contact with any external part of the human body' (this includes the mouth and teeth). We use cosmetics to cleanse, perfume, protect and change the appearance of our bodies or to alter its odours. In contrast, products that claim to ‘modify a bodily process or prevent, diagnose, cure or alleviate any disease, ailment or defect’ are called therapeutics. This distinction means that shampoos and deodorants are placed in the cosmetics category, whilst anti-dandruff shampoos and antiperspirants are considered to be therapeutics.
Regulation and safety
In Australia, the importation, manufacture and use of chemicals—including those used in cosmetics—are regulated by the Australian Government’s National Industrial Chemicals Notification and Assessment Scheme (NICNAS). NICNAS works to ensure that chemicals used in consumer products do not cause significant harm to users or to the environment.
In the case of cosmetics, every ingredient contained within the product must be scientifically assessed and approved by NICNAS before being manufactured or imported into Australia and before they can be used in consumer products. Where appropriate, NICNAS sets limits on the level at which a chemical can be used in a product and also conducts reviews on chemicals when new evidence arises.
Cosmetic products that make an additional therapeutic claim (such as moisturisers that also lighten the skin) are regulated by a different organisation—the Therapeutic Goods Administration (TGA).
Cosmetics and other personal care items must also be labelled in accordance with the Trade Practices (Consumer Product Information Standards, Cosmetics) Regulations 1991. This regulation requires that all intentionally added ingredients are listed on the product label, and is enforced by the Australian Competition and Consumer Commission (ACCC).
What do cosmetics contain?
There are thousands of different cosmetic products on the market, all with differing combinations of ingredients. In the United States alone there are approximately 12,500 unique chemical ingredients approved for use in the manufacture of personal care products.
A typical product will contain anything from 15–50 ingredients. Considering the average woman uses between 9 and 15 personal care products per day, researchers have estimated that, when combined with the addition of perfumes, women place around 515 individual chemicals on their skin each day through cosmetic use.
But what exactly are we putting on our skin? What do those long names on the ingredient list mean and what do they do? While the formula of each product differs slightly, most cosmetics contain a combination of at least some of the following core ingredients: water, emulsifier, preservative, thickener, emollient, colour, flavors and fragrances and pH stabilisers.
If your product comes in a bottle, chances are the first ingredient on the list is going to be water. That’s right, good old H2O. Water forms the basis of almost every type of cosmetic product, including creams, lotions, makeup, deodorants, shampoos and conditioners. Water plays an important part in the process, often acting as a solvent to dissolve other ingredients and forming emulsions for consistency.
Water used in the formulation of cosmetic materials is not your everyday, regular tap water. It must be ‘ultra-pure’—that is, free from microbes, toxins and other pollutants. For this reason your label may refer to it as distilled water, purified water or just aqua.
The term emulsifiers refers to any ingredient that helps to keep unlike substances (such as oil and water) from separating. Many cosmetic products are based on emulsions—small droplets of oil dispersed in water or small droplets of water dispersed in oil. Since oil and water don't mix no matter how much you shake, blend or stir, emulsifiers are added to change the surface tension with surfactant materials between the water and the oil, producing a homogeneous and well-mixed product with an even texture. Examples of emulsifiers used in cosmetics include polysorbates, laureth-4, and potassium cetyl sulfate.
Preservatives are important ingredients. They are added to cosmetics to extend their shelf life and prevent the growth of microorganisms such as bacteria and fungi, which can spoil the product and possibly harm the user. Since most microbes live in water, the preservatives used need to be water-soluble, and this helps to determine which ones are used. Preservatives used in cosmetics can be natural or synthetic (man-made), and perform differently depending on the formulation of the product. Some will require low levels of around 0.01%, while other will require levels as high as 5%.
Some of the more popular preservatives include parabens, benzyl alcohol, salicylic kojic acid, formaldehyde and tetrasodium EDTA (ethylenediaminetetra-acetic acid).
Consumers who purchase ‘preservative-free’ products should be aware of their shorter shelf life and be conscious of any changes to the look, feel or odour of the product that may indicate it has gone off.
Thickening agents work to give products an appealing consistency. They can come from four different chemical families:
Lipid thickeners are usually solid at room temperature but can be liquefied and added to cosmetic emulsions. They work by imparting their natural thickness to the formula. Examples include cetyl alcohol, stearic acid and carnauba wax.
Naturally derived thickeners come, as the name suggests, from nature. They are polymers that absorb water, causing them to swell up and increase the viscosity of a product. Examples include hydroxyethyl cellulose, guar gum, xanthan gum and gelatin. Cosmetics with a consistency that is too thick can be diluted with solvents such as water or alcohol.
Mineral thickeners are also natural, and as with the naturally derived thickeners mentioned above, they absorb water and oils to increase viscosity, but give a different result to the final emulsion than the gums. Popular mineral thickeners include magnesium aluminium silicate, silica and bentonite.
The final group are the synthetic thickeners. They are often used in lotion and cream products. The most common synthetic thickener is carbomer, an acrylic acid polymer that is water-swellable and can be used to form clear gels. Other examples include cetyl palmitate, and ammonium acryloyldimethyltaurate.
Emollients soften the skin by preventing water loss. They are used in a wide range of lipsticks, lotions and cosmetics. A number of different natural and synthetic chemicals work as emollients, including beeswax, olive oil, coconut oil and lanolin, as well as petrolatum (petroleum jelly), mineral oil, almond oil, glycerine, zinc oxide, butyl stearate and diglycol laurate.
Ruby lips, smoky eyes and rosy cheeks; it is the purpose of many cosmetics to accentuate or alter a person’s natural colouring. A huge range of substances are used to provide the rainbow of appealing colours you find in the makeup stand. Mineral ingredients can include iron oxide, mica flakes, manganese, chromium oxide and coal tar. Natural colours can come from plants, such as beet powder, or from animals, like the cochineal insect. The latter is often used in red lipsticks and referred to on your ingredient list as carmine, cochineal extract or natural red 4.
Pigments can be split into two main categories: organic, which are carbon-based molecules (i.e. organic in the chemistry context, not to be confused with the use of the word to promote ‘natural’ or ‘non-synthetic’ or ‘chemical-free’ products) and inorganic which are generally metal oxides (metal + oxygen and often some other elements too). Inorganic should not be confused with ‘synthetic’ or ‘unnatural’ as most of the inorganic metal oxide pigments do occur naturally as mineral compounds.
The two most common organic pigments are lakes and toners. The lake pigments are made by combining a dye colour with an insoluble substance like alumina hydrate. This causes the dye to become insoluble in water, making it suitable for cosmetics where water-resistant or waterproof properties are desired.
A toner pigment is an organic pigment that has not been combined with any other substance.
The inorganic metal oxide pigments are usually duller than the organic intermediate pigments, but are more resistant to heat and light, providing a longer-lasting colour.
Glimmer and shine
Shimmering effects can be created via a range of materials. Some of the most common ones are mica and bismuth oxychloride.
Cosmetic mica typically comes from muscovite (KAl2(AlSi3O10)(F,OH)2) also known as white mica. It naturally forms in flaky sheets and these are crushed up into fine powders. The tiny particles in the powders refract (bend) light, which creates the shimmering effect common in many cosmetics. Mica coated with titanium dioxide gives a whitish appearance when looked at straight on, but then produces a range of iridescent colours when viewed from an angle.
Bismuth oxychloride (BiClO) is used to create a silver grey pearly effect. This compound occurs naturally in the rare mineral bismoclite, but is usually produced synthetically and so is also known as synthetic pearl.
The size of the particles used to create pearly and shimmering looks affect the degree of glimmer the product has. The smaller the particle size (15–60 microns, where one micron is one millionth of a meter), the less lustrous the powder will be, and more coverage it gives. Larger particle sizes, up to 500 microns, give a more glittery lustre and are more transparent.
No matter how effective a cosmetic may be, no one will want to use it if it smells unpleasant. Consumer research indicates that smell is one of the key factors in a consumer’s decision to purchase and/or use a product.
Chemicals, both natural and synthetic, are added to cosmetics to provide an appealing fragrance. Even ‘unscented’ products may contain masking fragrances to mask the smell of other chemicals.
The term ‘fragrance’ is often a generic term used by manufacturers. A single listing of fragrance on your product’s ingredient list could represent dozens or even hundreds of unlisted chemical compounds which were used to create the final individual fragrance.
Manufacturers do not have to list these individual ingredients as fragrance is considered to be a trade secret.
There are over 3,000 chemicals used to formulate the huge range of fragrances used in consumer products worldwide. A comprehensive list has been published by the fragrance industry. All the ingredients on this list have passed the International Fragrance Association (IFRA) safety standards for use in commercial products. However, without knowing which individual ingredients went in to making up the fragrance of a product, consumers can find it difficult to make informed choices. If consumers are concerned they should look for fragrance free products and buy from companies that label their products more comprehensively.
Are cosmetics dangerous?
There’s nothing like a bit of controversy to generate some media buzz. For over a decade there have been recurring reports in both the media and on hundreds of internet sites relating to potentially toxic substances present in cosmetics (lead, mercury, parabens) and the dangers they pose to the public. Should consumers be worried? Are these claims backed up by reputable, published scientific research or have the findings been misinterpreted and exaggerated? Let’s take a look …
Parabens are a class of chemicals commonly used as preservatives in food, therapeutic and cosmetic products. They are derived from para-hydroxybenzoic acid (PHBA), which occurs naturally in many fruits and vegetables. Parabens come in several forms: methylparaben, ethylparaben, propylparaben, butylparaben and isobutylparaben. They are the most widely used preservative in personal care products. This is because they are incredibly good at doing their job—keeping your products mould and bacteria free—and are also cost effective.
The use of parabens in cosmetics hit the media in 2004 after a research study conducted by Dr. Philippa Darbre of the University of Reading in England reported findings that 18 out of 20 breast cancer tissue samples contained parabens. As parabens can weakly mimic the actions of oestrogen, and as oestrogen can enhance tumour growth, this was thought to be a problem. The presence of parabens in breast tumours was picked up by the media and presented as evidence that parabens contribute to breast cancer. This was incorrect.
While the presence of parabens is notable, the study found no direct evidence that they had caused the cancer or contributed to its growth. Breast tumours have a large blood supply, so it is likely that any chemical found in the blood stream will be present in the tumour.
In a later statement to the media, Dr. Darbre, referring to her 2004 study, said ‘No claim was made that the presence of parabens has caused the breast cancers.’
There have since been dozens of studies undertaken around the globe on the safety of parabens, which time and again have exhaustively demonstrated that parabens are broken down, metabolised and excreted harmlessly from the body.
Currently, both in Australia and internationally, the science community consider the use of parabens in cosmetics to be safe.
In response to consumer demand, some companies have begun to manufacture paraben free products, which consumers can purchase if they are concerned.
Concerns regarding cancer are also linked to the use of aluminium in deodorants and anti-perspirants. In the early 2000s various news outlets reported apparent links between the use of antiperspirants containing aluminium and breast cancer. Similar reports connected the use of such products to the onset of Alzheimer’s disease. These supposed links have never been scientifically proven despite multiple studies.
Aluminium works to block the sweat ducts to reduce sweating. Some argue that this process prevents us from releasing toxins, causing them to build up within our lymph glands. However, breast cancer tumours do not originate in the lymph nodes, they start in the breast, and travel to the lymph nodes later. Another study found no difference in the concentration of aluminium between the cancer and the surrounding tissue.
Currently there is no clear link between the use of under-arm products containing aluminium and breast cancer.
Likewise, studies have shown no relationship between Alzheimer’s disease and deodorant/antiperspirant use. Every day, humans are exposed to aluminium through food, packaging, pots and pans, medicine and even air and water. The official position of both the Alzheimer’s Society (US) and Alzheimer’s Australia is that a link between environmental aluminium absorption and Alzheimer’s disease seems ‘increasingly unlikely’.
Despite these findings, some manufacturers have begun producing aluminium-free products for consumers who still hold concerns.
Triclosan was originally developed as an anti-bacterial agent for use in hospitals, primarily as a surgical scrub. However its usefulness has seen it increasingly added to a wide range of consumer products including deodorant, soap, toothpaste, cosmetics and general house-hold cleaning products. Triclosan is also used as a pesticide and can, under certain circumstances, break down into potentially toxic chemicals such as dioxins.
Triclosan hit the news in 2000 after findings published by the National Academy of Sciences (US) noted rising levels of the chemical being detected in the environment and its increasingly broad use in everyday products as concerns.
Studies conducted by scientists at the University of California found that prolonged exposure to triclosan causes liver fibrosis and cancer in laboratory mice. Other studies have suggested triclosan can disrupt hormones, impair muscle contraction and reduce bacterial resistance.
Whilst the over-use of triclosan in products warrants further study, Australian experts have highlighted its value and importance when used correctly and in moderation. Professor of Dental Science at the University of Queensland, Dr. Laurie Walsh, noted that the chemical has been proven to fight various conditions such as gingivitis, inflammation and bleeding gums.
In Australia, a full risk assessment conducted by NICNAS found no cause for public concern in general, though did recommend controls for maximum concentrations of triclosan (0.3%) in personal care and cosmetic products. At present, cosmetic products containing more than 0.3% triclosan must clearly carry the word ‘poison’ on the label—not the best marketing strategy for producers.
The American Food and Drug Administration (FDA) is planning to release an updated report on Triclosan in 2016, though in the interim consumers may look for triclosan-free products if they wish.
Formaldehyde is an organic compound with a wide variety of uses. Although commonly associated with embalming, it is also used in the manufacture of building materials, textiles, household cleaning products, plastics, cosmetics and personal care products. It also occurs naturally in a wide range of foods, for example the humble egg.
Formaldehyde is not typically used in its pure form, but altered slightly and listed under the name formalin. It works as a preservative to protect products from contamination.
Formaldehyde is classified as a Group 1 carcinogen (known to cause cancer in humans) by the World Health Organization International Agency for Research on Cancer. It can also cause skin and sensory irritation and breathing difficulties in people when inhaled, ingested or if it comes into contact with skin. So why is it still used in everyday products?
As with other chemicals, it is the concentration present in a product that is important. NICNAS has assessed formaldehyde and set maximum safe limits for its use in cosmetics. Oral products such as toothpastes may only contain up to 0.1 percent formaldehyde, while nail hardeners can have up to 5 percent. All other cosmetic products (such as shampoos and straightening solutions) can have up to 0.2 percent. At these low levels, the use of formaldehyde is deemed to be safe.
NICNAS has noted that people with particularly sensitive skin may still experience irritation even at these low concentrations.
In 2010, the Australian Competition and Consumer Commission (ACCC) conducted a survey of the formaldehyde concentrations of several cosmetic products that resulted in the voluntary recall of two products that contained unacceptably high concentrations of the chemical.
Phthalates (pronounced THAL-ates) are another group of chemicals found in some cosmetics that have been red-flagged by environmental groups. They are generally used to make plastic products soft and flexible but can also be found in cosmetics like nail polish, hair spray (to make the products less brittle or stiff) and perfumes.
Phthalates are produced from oil and there are more than 20 types in common use. As the various phthalates have different chemical structures, toxicity profiles and uses, their safety should not be generalised as a group, but looked at on an individual basis. Some studies have indicated that at high, recurring concentrations different phthalates can act as endocrine disruptors—this means they upset the hormonal balance in the body and can lead to developmental problems, particularly in males. Other studies have indicated there may be a link between phthalates and type 2 diabetes.
In response, the European Union and the United States have imposed bans on some types of phthalates for use in cosmetics. Research conducted in Australia has identified a small level of risk in relation to one phthalate, bis(2-ethylhexyl) phthalate or DEHP, and as a result NICNAS has prohibited products that contain DEHP above the prescribed level—this generally relates to children’s toys.
Lead in your lipstick?
News reports detailing levels of lead and other metals in lipsticks are persistent and recurring, but should consumers be worried? A 2013 study by the University of California Berkley examined the metal content of 32 different lipsticks. Researchers found traces of aluminium, manganese (which can cause neurological problems) and titanium in all the products they tested, while three-quarters of the products contained lead (which affects the nervous system, and can cause learning disabilities in children). Many of the lipsticks and lip glosses also contained nickel and cobalt, as well as cadmium and chromium—both known carcinogens.
Why would manufacturers add these ingredients to their products? The answer is—they don’t. They exist in the products as ‘impurities’, that is, they are present in other ingredients such as the wax, oils or the mineral pigments used in the formula. Because of the persistent nature of these substances and the fact they occur in the natural environment, including in water, it is almost impossible to remove all traces of them.
However don’t throw your lippy away just yet. The presence of these naturally-occurring elements in lipsticks is not necessarily a problem—the important issue is the level or concentration. Are the the levels high enough to be considered toxic, or are they low enough to be deemed safe? Remember, sunlight is also a proven carcinogen (skin cancer)—but you still go outside and you might even sunbathe. It all comes down to dose.
With the exception of chromium, the study concluded that the metal concentrations were comfortably within the ‘acceptable daily allowances’ as determined by the researchers via a comparison with accepted water and air contamination levels. Basically, you will consume more lead from drinking water than you will from applying lipstick. However, the study did conclude that further research into the metal content of cosmetic products is necessary, particularly with respect to chromium.
While sun creams are not officially cosmetics (they are considered to be therapeutics), we will include them here as their use is so common, particularly in Australia.
Sunscreens play an important role in protecting our skin from the harmful UVA and UVB rays emitted by the sun. Their use has been proven to help prevent certain skin cancers including melanomas and basal cell carcinomas.
In recent years there has been some concern about nanoparticles (NP) in sunscreens. This relates particularly to zinc oxide (ZnO) and titanium dioxide (TiO?) nanoparticles and their ability to penetrate the skin to reach cells and the potential toxicity exerted by these chemicals.
The position of the Therapeutic Goods Administration (TGA), based on several published papers (up to May 2013) as well as reviews of international authorities, is that nano-particles are safe. ‘Several in vitro and in vivo studies using both animal and human skin have shown that these NPs do not penetrate the underlying layers of skin, with penetration limited to the stratum corneum. This suggests that systemic absorption is unlikely.’
A further study published in 2014 found that when exposed to zinc oxide nanoparticles, human immune cells (called macrophages) effectively absorbed the nanoparticles and broke them down.
Based on current evidence, neither TiO2 nor ZnO nanoparticles are likely to cause harm when used as ingredients in sunscreens. There are more risks associated with avoiding suncreams (sunburn, skin cancers) than there are posed by nanoparticles.