Cetearyl alcohol often appears on ingredient lists
We all know what fat is. And we all know what alcohol is. But how about a fatty alcohol?
Chemically speaking there isn’t much difference between a fat and an oil. The definition is basically that if it is solid it is a fat, if it is liquid it is an oil. But they are all triglycerides, made up of long fatty or oily chains three of which are linked to a glycerin. If you break down a fat you get glycerin and fatty acids. It is easy to separate these because glycerin is soluble in water so you just wash it out. You are then left with the fatty acids. There are a lot of different kinds of fatty acid but they all share the same basic structure of having a long fat chain with a reactive acid group at the end. Stearic acid is a typical example.
The acid group can be a nuisance because of its reactivity, so the acid group can be transformed into a much less reactive alcohol. And there you have your fatty alcohol. In fact the conversion to an alcohol makes a very interesting waxy material. Fatty alcohol chains come in all shapes and sizes and by playing around with different proportions of different alcohols you can get quite a lot of control of the texture of the product you are making.
Cetearyl alcohol is a blend of cetyl and stearyl alcohol and is popular with formulators of beauty products because it is a very versatile choice. It is used in loads of different kinds of products from baby oils to shampoos, but is really useful in skin creams. When you look on ingredient lists you will see that sometimes a whole set of fatty alcohols have been used – this is often evidence of someone spending ages fiddling to get just the effect that they are after. I’ve put a list of some popular fatty alcohols at the bottom of the post. If this post proves popular I might do so posts on some of the other fatty alcohols.
Cetearyl alcohol and the other fatty alcohols have had a fairly easy ride from the scaremongers. But the Environmental Working Group rarely let you down when you are looking for nonsense. The Skin Deep database lists it as a suspected environmental toxin. Given that it is easily biodegradable I can’t imagine what gives rise to these suspicions. If you asked the average micro-organism it would probably describe it as not just as readily biodegradable but as positively tasty. Another surprising concern was expressed to me once by a very intelligent and well educated young muslim woman who noticed the word alcohol on the ingredient list for, if I remember rightly, Vaseline Intensive Care Lotion. She was bothered as to whether using it would violate her religion’s ban on alcohol. I was able to reassure her that it had nothing to do with alcohol produced by fermentation.
Another issue is the source of the fat or oil from which the fatty alcohol is derived. Triglycerides are found in all kinds of living organisms. It is perfectly possible to get them from plant or animal sources – or even from more unconventional feedstocks. I doubt it will ever be economical to do so, but it would be quite feasible to produce them from micro-organisms via some kind of biotechnology.
A story went round a couple of years ago that a gang in Peru were extracting fat from human victims for use in cosmetics. It was a gruesome story but the chemistry was straightforward enough. Humans would make as good a source as any. But as exactly the same material can easily be produced from plant sources cheaply and in great quantities I am not sure what exactly the motivation of the Peruvian villains was. The bulk of feedstocks for the cosmetics industry has always been plants, but tallow was used as well until recently. This stopped with the BSE crisis. Governments around the world brought in regulations to ensure that BSE could not get into the food chain. This had the effect of making animal sourced fats more expensive and that has to all intents and purposes stopped their use. Vegetarians would probably be pleased to hear that, but I don’t think any company has made a point of highlighting its vegetarian status.
Fatty alcohols related to Cetearyl alcohol
Notes for Chemists
The CAS numbers for cetearyl alcohol are 67762-27-0 and 8005-44-5. Cetearyl alcohol is the name that you have to use on an ingredient list but it is usually referred to as cetostearyl alcohol. No safety concerns have ever been raised with this material and it is so easily made that it is a very cost effective material in most applications. The thing to watch out for though is the differences between grades. Because it is a blend of fatty alcohols the distribution of chain lengths can vary a lot from supplier to supplier. Particularly where it is being used as an emulsion stabiliser the more diverse the chain length the better it is. Purer is definitely not better. The chain length distribution will have a big effect on the liquid crystal structure too, so it might well affect how actives are delivered from a formulation. Just because this material is cheap and familiar doesn’t mean a formulator can fail to treat it with respect.