Alcohols in skincare products

Today’s topic was suggested by my lovely housemate, WL! J

Should we avoid skincare products containing alcohol? There are already many articles out there on the internet discussing and debating this issue. Many articles also talk about “good” alcohols and “bad” alcohols for the skin.

Before we explore this topic further, let’s do a short revision of some ‘A’-level organic chemistry:

Chemical structures of alcohols

In chemistry, the term “alcohol” refers to any of a class of organic compounds characterized by one or more hydroxyl (−OH) groups attached to a carbon atom of an alkyl group (hydrocarbon chain, represented as R in the drawing above). (Definition from Encyclopaedia Britannica.)

The alkyl group, R, can vary in length from short hydrocarbon chains (e.g. ethanol, isopropanol) to long hydrocarbon chains (e.g. stearyl alcohol, cetyl alcohol).

Short chain alcohols

1.       Ethanol (also known as ethyl alcohol. It is also the major ingredient in denatured alcohol or SD alcohol.) This is the alcohol that we drink!

  

2.       Isopropanol (also known as isopropyl alcohol)

Short chain alcohols are the alcohols which are commonly said to be “bad” for the skin as they can disrupt the skin’s protective barrier and dry up the skin. In my opinion, these are not necessarily bad ingredients as they can help to dissolve active ingredients in the product & also help increase the absorption of active ingredients by the skin. (See my previous post on skin penetration enhancers.) But if you have dry skin or eczema, then you may want to avoid products containing these alcohols which can worsen the dryness.

Long chain alcohols

Due to their long hydrocarbon chains, long chain alcohols tend to be greasy/waxy and make good moisturisers. Hence, many articles call them the “good” alcohols.

1.       Cetyl Alcohol 

2.       Stearyl alcohol 

3.       Cetearyl alcohol (which is a mixture of long chain alcohols, mainly cetyl and stearyl alcohols)

4.       Lanolin Alcohol (also known as wool alcohol, produced from lanolin or “wool fat”)

A word of caution though: some people may be allergic to lanolin.

Some other alcohols…

Besides short-chain and long-chain alcohols, some other ingredients also contain “ol” or “alcohol” in their names. Here’s just a few examples:

1.       Glycols (propylene glycol, butylene glycol), glycerol (also known as glycerin)

 

Chemical structures of propylene glycol and glycerol

I suppose most people wouldn’t think of these ingredients as alcohols, but I shall include them here anyway since they are commonly found in skincare products too. LOL. Glycols have 2 –OH groups in their chemical structure, while glycerol has 3. These compounds are humectants, which bind water and help moisturise the skin.

2.       Phenoxyethanol

3.       Dichlorobenzyl alcohol (also used as an antiseptic in Strepsils lozenges!)

 

Chemical structures of phenoxyethanol and dichlorobenzyl alcohol

Both phenoxyethanol and dichlorobenzyl alcohol possess antibacterial activity, so they are sometimes used as preservatives in skincare products.

4.       Vitamins such as retinol (vitamin A), calcitriol (vitamin D), α-tocopherol (vitamin E)

From the different examples mentioned above, we can see that “alcohols” describes huge class of compounds, and different alcohols can have very different effects on our skin. I hope that this blog post has given you a better idea of some of the different types and functions of alcohols used in skincare products. J