A slick of red lipstick can transform a look from unremarkable to ultra-glam in seconds, and it’s been a beauty staple for thousands of years. Women in Ancient Egypt used crushed insects and toxic seaweed paste to redden their lips, whilst the Mesopotamians used the dust of semi-precious jewels and fish scales to add colour and lustre. Compared to these less-than-lovely historical recipes modern lipstick seems harmless, but has still been the subject of some controversial debates about the safety of the ingredients used. As the only cosmetic likely to be ingested (even in very small amounts!) it’s vital to know exactly what goes into a tube of lipstick, and what effects the ingredients might have on the body chemistry of the wearer.

So, what is lipstick made of?

The formula will differ between brands and types of lipstick (glossy, matte, moisturising etc.) but all will contain a mixture of waxes, oils, pigments and fragrance. The waxes provide the structure of the lipstick, and are usually natural products such as beeswax and carnauba, a wax obtained from palm leaves and particularly useful due to its high melting point (82 – 86 ◦C) which prevents lipstick from melting in the tube on sunny days! Oils such as silicone oil, olive oil, lanolin and cocoa butter help seal the product to the lips whilst providing gloss and moisturisation. Some lipsticks also intentionally contain skin irritants such as capsaicin, the molecule responsible for the heat in chili peppers, to cause temporary swelling of the lips and give a ‘lip-plumping’ effect.

Capsaicin

(The structure of capsaicin, or 8-Methyl-N-vanillyl-trans-6-nonenamide, a chemical agonist which binds to receptors signalling the body to produce an inflam- mation response. The long hydrocarbon chain gives it an oily texture, making it soluble in fats rather than water. So next time spicy food is a little too hot, reach for a glass of milk rather than water to cool stinging lips (unless you’re after the plumping effect of course!)).

Appropriately enough for a product applied to the mouth, most of the dyes used in lipstick manufacture are also approved as food colourants. Many of these are naturally derived (although now produced synthetically), such as carmine, an an- thraquinone linked to a glucose sugar moiety and originally extracted from the shells of cochineal beetles, or produced from petroleum, such as the popular azo dye ‘Al- lura Red AC’ (azo = containing two nitrogen atoms with a double bond between them within the molecular structure). These colouring agents have attracted some controversy as foodstuff dyes, with carmine considered a potentially serious allergen and Allura Red AC indicated in several studies as increasing the levels of hyperactivity and ADHD in children. However, this is less of a concern in lipstick as the amount likely to be consumed is very small (24 – 87 mg per day of wear) and so health problems are are unlikely to result.

carminic acid

(The structure of carminic acid, or 7-α-D-Glucopyranosyl-9,10-dihydro- 3,5,6,8-tetrahydroxy-1-methyl-9,10-dioxoanthracenecarboxylic acid, the colouring agent found in carmine.)

allura red

(The structure of Allura Red AC (Red Dye #40), or disodium 6-hydroxy- 5-((2-methoxy-5-methyl-4-sulfophenyl)azo)-2-naphthalenesulfonate. The multiple double bonds present in this are responsible for its strong colour.)

Of more pressing concern is the level of various metals found in lipsticks. A US study from 2007 analysed 33 popular lipstick brands and found low-level lead contamination in 61% of them.1 There were also traces of aluminium, cadmium, chromium and manganese, all of which are toxic to humans. Aluminium has been linked to dementia, cadmium exposure can cause flu-like symptoms and it’s a suspected carcinogen, as is chromium, which also causes stomach ulcers. Manganese and lead both damage the nervous system. Most of these effects only occur following an in- take of high levels of the metal, although there are still legitimate hazards associated with long-term exposure. Lead, for example, has a low rate of skin absorption but is a cumulative poison, so low-level exposure over many years may result in a build-up of lead in body tissue. This is particularly problematic if there is also exposure from other sources, such as soil contamination and atmospheric pollution. The EU specifically bans the use of lead and its salts in cosmetic products, but recognises that lead is a naturally occurring element and it may not be possible to eliminate contamination entirely.

1Levels ranged from 0.03 to 0.65 ppm. Following on from this, a further study in 2012 tested 400 lipsticks and found lead levels of up to 7.19 ppm. The limit set by the US Food and Drug Administration for lead in sweets is 0.1 ppm, although cosmetics and foodstuffs are not strictly comparable as the former are not intended for ingestion.

2The Cosmetic, Toiletry & Perfumery Association (CPTA) is the organisation responsible for representing companies involved in making, supplying and selling cosmetic and personal care prod-

Concerns have been raised over the fact that there is no legal requirement for lip- sticks to be labelled as containing trace metals, or any regulation as to the levels they may be present in. Indeed, although most of the metals mentioned here are contaminants from machinery used in the manufacturing process, aluminium is in- tentionally added to the natural pigments discussed above in order to convert them from water-soluble dyes to insoluble ‘lakes’, thereby preventing lipstick washing off with every sip of water!

So does this mean lipstick should be confined to the back of the make up drawer, never to be applied again? Is the future of the perfect pout in jeopardy? The short answer is, thankfully, no. The bodies responsible for ensuring the safety of cosmetics do not consider low-level metal contamination in lipstick to pose a serious health threat, although consumer organisations are campaigning for better labelling and and a defined upper limit for these contaminants, lead in particular. The future of lipstick may well see these changes coming into use, allowing consumers to make more informed choices – always a good thing. Until then, there’s no need to throw out all your old lippy – just try not to swallow too much of it!

*Bonus Science* – Why is lead so toxic to humans?

The Biology Explanation

Lead poisons by displacing other metal cations in the body, particularly calcium, iron and zinc. These metals are important in regulating cellular processes, includ- ing haem synthesis, the disruption of which leads to anaemia. Lead can also form reactive radicals, damaging DNA and cell membranes and interrupting the release of neurotransmitters.

The Chemistry Explanation

Lead is in the same group of the periodic table as carbon, the element that forms the chemical basis of all known life. So why is it so toxic to humans? Well, although lead and carbon both contain four valence or ‘outer-shell’ electrons with which to potentially form bonds, they don’t behave in the same way. Of the four electrons, two are paired and reside in a spherical ‘s’ orbital, and two are unpaired and reside in two of the three p orbitals. Carbon uses a small amount of energy to rearrange its four electrons into four identical hybrid orbitals (labelled sp3). The energy cost of this rearrangement is offset by the fact that carbon is now capable of forming four strong covalent bonds rather than two, substantially lowering the energy of the molecule formed. With lead, this is not the case. There is a larger energy gap between the paired s electrons and the unpaired p electrons, so more energy would be needed to rearrange these electrons, and this energy would not be offset by forming more bonds. Therefore, lead tends to form two bonds and have a pair of electrons not involved in bonding (a ‘lone pair’). This is known as the inert-pair effect. The lone pair can get in the way quite dramatically, distorting the arrangement of atoms binding to lead. In enzymes, where shape is vital to function, this can be disastrous! Lead has no known physiological role in the body, and there is no agreed-upon safe threshold for lead exposure.

orbitals

(A diagram to show how the spherical s orbital and three dumbbell-shaped p orbitals can be hybridised to give four identical sp3 orbitals. This gives a tetrahedral configuration and is common in carbon-based structures. Lead does not hybridise its orbitals in this way, maintaining a lone pair of electrons in its outermost s orbital, which can disrupt the bonding of other atoms to lead.)

Capsaicin – sigma aldrich

Carminic Acid – sigma aldrich

Allura Red AC – sigma aldrich

“Food Additives and Hyperactive Behaviour in 3-year-old and 8/9-year-old Children in the Community: a Randomised, Double-Blinded, Placebo-Controlled Trial”, The Lancet, 2007, 370 (9598), 1560.

“Asthma and Allergy Due to Carmine Dye”, An. Sist. Sanit. Navar., 2003, 26 (2), 65.

Studies Relating to Cosmetic Safety and Lead in Lipstick

“Concentrations and Potential Health Risks of Metals in Lip Products”, Environ. Health Perspect., 2013, 121 (6), 705.

“Determination of Total Lead in 400 Lipsticks on the U.S. Market using a Validated Microwave-Assisted Digestion, Inductively Coupled Plasma-Mass Spectrometric Method”, J. Cosmet. Sci., 2012, 63 (3), 159.

“Determination of Total Lead in Lipstick: Development and Validation of a Microwave-Assisted Digestion, Inductively Coupled Plasma-Mass Spectrometric Method”, J. Cosmet. Sci., 2009, 60 (4), 405.

“Assessment of Lead in Cosmetic Products”, Regul. Toxicol. Pharmacol., 2009, 54 (2), 105.

Campaign for Safe Cosmetics (US) “A Poison Kiss: The Problem of Lead in Lipstick”, 2007 

“A Perspective on the Safety of Cosmetic Products: A Position Paper of the American Council on Science and Health”, Int. J. Toxicol., 2006, 25 (4), 269.

Statements from the FDA and CPTA on Lead in Lipstick

Statement from UK Government on Cosmetic Safety

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