CH₃-CH₂-OH. Behind this chemical formula lies ethanol, or ethyl alcohol, commonly known as just ‘alcohol’.
It is a primary alcohol obtained either by fermenting plants rich in sugars (fruit, cereal, sugar cane…), or with distillation. As a result, it can be called ‘natural’, or even sustainable, since it is agro-sourced and obtained with ‘green’ processes (extraction, fermentation, and distillation for beetroot; extraction, hydrolysis, fermentation, and distillation for cereal like wheat or corn). It can even be derived from organic farming.
Colourless and volatile, it is obviously contained in alcoholic drinks (wine, beer, aperitifs, liqueurs…), but also in a great number of cosmetics, as a raw material with multiple applications… On top of that, it is cheap.
Of course, it is mostly an essential in perfumery, as it makes up 70 to 95% of perfume bottles. It solubilizes the perfumed concentrate, which is composed of lipophilic components soluble in alcohol. It is also transparent, easily sprayed, and, due to its volatility, it evaporates after the application, so that only the perfumed concentrate is left on the skin.
Alcohol as a cosmetic active
It can make up from 0 to 20% of skincare formulas and fulfil various functions:
• Refreshing agent, for example in products for heavy legs
• Texturing agent, to make formulas lighter, in fluid sun products or aerosols
• Solubilizing agent in sun filters, which are lipophilic ingredients, or other actives like caffeine in slimming products
• ‘Distributing’ agent due to its volatility: it contributes to homogeneously distribute the fixating agents contained in styling gels in the hair, before quickly evaporating to let them act on the hair fibre
• Bacteriostatic agent, to contribute to preserving the formula, especially to reduce the use of ‘official’ preservatives…
Alcohol as a source of cosmetic ingredients
Ethanol is widely used to extract actives. Given its average polarity, this fluid solvent is very efficient and easy to use, since it remains liquid under normal pressure and temperature conditions, which helps solubilize natural or synthetic compositions. It also hardly interacts with the other actives in the formula, and can act on its own or in combination with other co-solvents:
• On its own, for example for the EtOH96 red vine extract rich in polyphenols
• Mixed with water for Pharmacopoeia extracts like the EtOH45 witch hazel extract rich in tannins
• Mixed with water and glycerine as a substitute for glycol extracts, in particular to obtain organic-certified actives
• As a co-solvent in supercritical CO2 extraction to extract more polar molecules than with CO2sc only
• As a purifying solvent, for example for the precipitation of polysaccharides or purification of rutin by crystallization…
Beware of hangovers
As regards its properties, alcohol, a substance that is also commonly used for other purposes, seems pretty attractive. And yet, any coin has two sides, so there are quite a few contraindications to its regular use.
On the skin surface
The skin may be the first to slightly suffer from repeated contacts with high quantities of alcohol… even if alcohol may be used on purpose in oily skin creams for its astringent effects. Its irritant potential (burning sensations, tingling, appearance of redness…) and its drying nature make it hardly commendable to use it too systematically, in particular on dehydrated and/or sensitive epidermises.
Of course, on the skin, its potential undesirable effects may vary considerably according to the percentage of alcohol used in the product… And the presence of soothing and moisturizing ingredients in the formula can offset them, partly or completely…
Be it as it may, alcohol seems particularly incompatible with a baby’s skin, which is thinner and more delicate than an adult’s, more easily irritable and prone to dehydration… especially since, as it is also more permeable, it helps alcohol penetrate the body more easily, in relatively more significant proportions: it can even be responsible for alcoholic disorders in newborn children!
In addition, it is photosensitizing (it can induce epidermal reactions in the presence of UV rays), so it should be avoided – in particular if it is used in high quantities – in all products likely to be applied before a sun exposure. Otherwise, it may trigger redness, irritations, or dermatitis…
Deep into the skin
The intrinsic dangers of alcohol have mainly been established in case of excessive oral consumption over a long period of time: its properties sound much less appealing in this context than when only its cosmetics functions are considered:
• Carcinogenicity: the prolonged ingestion of more than 50g/day over a period of 15 to 20 years is associated with some cancers (upper aero-digestive tract, colorectal tumour), and above 10g/day (the equivalent of one glass of an alcoholic drink), it can increase the risk of breast cancer
• Reproductive toxicity: starting from a consumption of 1g/day, it can reduce masculine fertility and lead to a decline in the libido or the atrophy of testicles, disrupt the menstrual cycle, provoke multiple congenital anomalies, starting from 10g/day, if the intoxication occurs during pregnancy (decline of the baby’s weight at birth, premature delivery…), and trigger behavioural disorders from 10 to 20g/day, or even severe anomalies in the physical and psychological development of the child
• Hepatotoxicity: alcoholism is also a factor leading to the accumulation of lipids in the liver, which can trigger cirrhosis and liver tumours
• Neurotoxicity: it can be acute (loss of inhibitions, and then sleepiness) or chronic, with the appearance of peripheral pathologies and disorders in the central nervous system
Given these parameters, alcohol was classified as a Group I carcinogen in 2007 by the IARC (International Agency for Research on Cancer), but only when alcoholic drinks are orally ingested.
The alcohol risk in cosmetics
Now, what about the risks associated with repeated contacts with the skin, at low doses… like with cosmetics?
A joint study was conducted by the AFSSET (French Agency for Environmental and Occupational Health Safety) and AFSSAPS (French Agency for Health Products Safety) in late 2008 to determine whether it also presented a risk for health, in particular in terms of reproductive toxicity, when individuals – even adults – are exposed to it through contact with the skin and/or by inhalation, at low doses: that is the case with cosmetics.
According to the cosmetics industry, if alcohol is quickly absorbed orally, it can easily get through the placental barrier and may end up in the mother’s milk, but its skin absorption is minimal – approximately 1%. Therefore, the systemic risk, that is, the dose of alcohol that might get to the blood system following the application on the skin of a product, even if it contains a high quantity of alcohol, is negligible.
As for lung absorption, which may occur with spray products or aerosols, it is more significant: about 60%. However, according to a study conducted by the cosmetics industry, as far as inhalation is concerned, exposure to alcohol through cosmetics is 7 to 70 times below the value considered as safe, 3 to 6 times for reproductive toxicity, and 6.5 times for the risk of breast cancer.
Conclusion: as such, alcohol in cosmetics allegedly represents no systemic risk for any consumer.
A few related effects?
Nevertheless, it should be emphasized that if skin absorption of alcohol itself is assessed at about 1%, which is really minimal, it is known for contributing to the transcutaneous penetration of certain cosmetic ingredients. It is true that in some cases, it may be part of the intended effect, without it being a major health problem. In other cases though, this property is much less welcome…
The case of denatured alcohol
Under European regulations, Alcohol denat. is ethyl alcohol denatured by agents qualified as denaturing in accordance with regulations, with a view to make it unsuitable for oral consumption.
In this case, the assessment of the final ingredient obviously depends a lot on the nature of the denaturing agents used to this aim. Indeed, in this category of compounds, there are both – as an example – acetone and menthol, or phthalates, in particular DEP, or Diethyl phthalate: these substances show quite different properties and associated risks.
And since regulations do not require it, this information can never be found on labels…
But things will change as from August 1
, 2017. Europe adopted
a regulation (No 2016/1867)
on October 20, 2016 to institute a single procedure for the common denaturing of alcohol and repeal all national denaturing procedures. From now on, the only denaturation process that may be used in all Member States, for completely denatured alcohol, will be the addition, per hectolitre of absolute ethanol, of:
• 1.0 litre isopropyl alcohol (IPA)
• 1.0 litre methyl ethyl ketone (MEK)
• 1.0 gram denatonium benzoate
How to behave with alcohol
At the end of the day, what solution should be adopted with alcohol in cosmetics?
It is now clear that certain products would not exist without it, but… just like when we are having a drink, we should show moderation.
In short, if we do use alcohol, it is better in low quantity, and not every day.
And we had better not use it at all on babies and sensitive and reactive skins, or skins prone to dryness.
Still, beware if you want to join the temperance league, all ‘alcohol’ designations in the lists of ingredients (like Benzyl alcohol, Behenyl alcohol, Cetearyl alcohol, and many others…) do not refer to ethanol, which is only named Alcohol or Alcohol denat. in INCI lists.© CosmeticOBS-L'Observatoire des Cosmétiques