Alcohol denat. in skincare: what it is and why it is used

Ethanol, made undrinkable

CosIng defines Alcohol Denat. as ethyl alcohol denatured with one or more denaturing agents in accordance with the national legislation of each EU country. Alcohol on its own is undenatured ethyl alcohol.¹²

Denaturing stops misuse. The FDA explains that ethyl alcohol in a cosmetic may be denatured to prevent it being diverted illegally for drinking: an added denaturant makes it undrinkable.³ It also matters for tax. In the EU, alcohol used to make a product not meant for human consumption is exempt from alcohol excise duty, provided it has been denatured to the requirements of a member state.⁴

CosIng defines a denaturant as an ingredient that renders cosmetics unpalatable, mostly added to products containing ethyl alcohol.⁵ One is Denatonium Benzoate,⁶ which the US Cosmetic Ingredient Review panel found bitter enough to work at only 0.0006%. The panel also names t-butyl alcohol, diethyl phthalate, methyl alcohol, salicylic acid, sodium salicylate and methyl salicylate as denaturants.⁷

On US packs, denatured ethanol often appears as SD Alcohol, for specially denatured alcohol, followed by a number such as 40-B that records how it was denatured under a federal formulary. Alcohol Denat. was introduced in Europe as a generic name, and dual listings such as SD Alcohol-40 (Alcohol Denat.) also occur.³

What it does in a formula

CosIng lists six functions for Alcohol Denat.: antifoaming, antimicrobial, astringent, fragrance, solvent and viscosity controlling.¹ It defines a solvent as dissolving other components, antimicrobial as preventing or slowing microbial growth, and astringent as contracting or tightening the skin.⁵

The antimicrobial role can affect how a product is preserved. EU working-group guidance on cosmetic claims notes that fine fragrances usually contain so much alcohol that preservatives are not needed. It adds that a "free from preservatives" claim should not be used when a product contains an ingredient that protects against microorganisms but is not on the EU list of preservatives, such as alcohol.⁸

Ethanol also changes how other ingredients behave on skin. The US panel notes that, applied to the skin, it can act as a penetration enhancer,⁷ and a 2008 review adds that it may help other substances in a formula pass through the skin.⁹

Not the same as fatty alcohols

"Alcohol" is a family name. In cosmetic labelling, the FDA says, the word alcohol on its own means ethyl alcohol, while cetyl, stearyl, cetearyl and lanolin alcohol are fatty alcohols whose effects on the skin are quite different. Isopropyl alcohol, it adds, is rarely used in cosmetics.³ CosIng lists Cetearyl Alcohol and Cetyl Alcohol as emollients, emulsifiers and viscosity controllers, among other roles; their own pages explain them.¹⁰¹¹

The checker's Drying alcohol group follows that line. It matches only names that identify ethanol: Alcohol, Alcohol Denat. and names beginning SD Alcohol, with Ethanol and Denatured Alcohol on a label resolving to these. Fatty alcohols, benzyl alcohol and other alcohols are never members.

Does it dry the skin?

Some people choose alcohol-free products because they believe ethyl alcohol dries their skin or hair, the FDA notes.³ The checker's group exists for the same reason: some people with dry or sensitive skin avoid products high in ethanol because they find it drying or tightening.

A 2008 review found the evidence pointing both ways. In one study in people, ethanol entered the skin and removed measurable amounts of lipid from its outer layer, which may lower its barrier function; yet repeated use of alcohol-based hand rubs did not significantly change water loss through the skin, skin water content or sebum. Ethanol is also associated with skin irritation or contact dermatitis, especially in people with an aldehyde dehydrogenase deficiency.⁹

The US panel wrote that ethanol does not appear to affect the integrity of the skin barrier, and based its conclusions on the safety of each denaturant: it found the data sufficient for denatonium benzoate and several others, but not for quassin or brucine.⁷ The formulations tested for that review ranged from 12% to more than 70% SD alcohol,⁷ and a label gives no percentage, only an order.¹² Ingredient list order explains what a position can show.

What "alcohol-free" means

In the US, the FDA explains that manufacturers have long marketed products without ethyl alcohol as "alcohol free", and that such products may still contain fatty alcohols such as cetyl, stearyl, cetearyl or lanolin alcohol.³

In the EU, "free from" claims are judged against common criteria, and the working-group guidance says a product claiming to be free of an ingredient should not contain it. It gives "free from alcohol", for example on a mouthwash meant for the whole family, as a claim that should be permitted when it meets the other criteria.⁸

On an ingredient list, Alcohol on its own means ethanol in both the US and the EU.³² So check the list for Alcohol, Alcohol Denat. or an SD Alcohol name, and do not read a fatty alcohol as a contradiction. Other pack wording is covered in the skincare label claims glossary.

On the label

• Alcohol or Alcohol Denat. is ethanol; SD Alcohol with a number is the US name for the denatured kind.³
• Cetyl, Stearyl, Cetearyl or Lanolin Alcohol are fatty alcohols, not ethanol.³
• A denaturant may appear further down, such as Denatonium Benzoate.⁶
• Position is the only clue to amount. Near the top of the list, ethanol is one of the larger ingredients by weight.¹²
• Run the list through the skincare ingredient checker, which marks Drying alcohol names and leaves fatty alcohols unmarked.