when you look at the ingredient lists of products like shower gel, conditioner etc. there are often several types of alcohol included…what’s the difference between these alcohols?

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A shower thought of mine haha

In: Chemistry

An “alcohol” is actually a class of molecules that are related in their molecular structure. The one we drink is called “ethyl alcohol”, but there are a lot of different ones. They have different consistencies, odors, abilities to dissolve substances and volatility. So depending on what the manufacturer wants, you add the kind that makes sense.

Alcohol does not inherrently mean drinking alcohol.

An alcohol is simply defined as any organic compound that carries at least one hydroxyl functional group (C-OH) bound to their aliphatic structure.

Ethanol is one type of alcohol, which we distill and ferment from sugars found in a variety of grains/starches/corn/fruits, etc. This is the alcohol that we drink in beer/liquor/wine.

Other common, but certainly not safe for consumption alcohols are Methanol (commonly known as wood alcohol) and Isopropanol (also known as rubbing alcohol). There are also a large number of OTHER alcohols which are all different types of solvents, precursors, preservatives, and fuels.

https://en.wikipedia.org/wiki/Alcohol

You might see something like Cetyl alcohol or Cetearyl alcohol, which are fatty alcohols used as thickeners and conditioner boosters. You might see a glycol, like propylene glycol, or a sugar alcohols, like xylitol, which work as humectants to draw water from the atmosphere to hydrate skin or hair, bind water, reduce the freezing point of the product, boost preservatives, or act as a solvent for other ingredients, like extracts. And you can find liquid alcohols, like rubbing alcohol or denatured alcohol, which act as solvents, offer a cool, refreshing “fresh kick”, and can be used as preservatives if they are in high quantities.

As a cosmetic hobbyist, I can explain this very simply. Alcohols do different things. And generally, cosmetic ingredients tend to have more than one effect.

Cetyl Alcohol: Stabilizes the emulsions. It has humectant(the skin will stay hydrated) properties. It also makes the cosmetic opaque. You can add oils and fats instead of cetyl alcohol, but the ingredient wouldn’t be stable. It would be hard in Canada, more creamy in Turkey.

Cetearyl Alcohol: Similar to cetyl alcohol. But has different texture in cosmetics.

Ethyl Alcohol: Mostly used in perfumes and body mists. It’s a solvent. Makes perfume smell more powerful. Used as a preservative if it’s added a lot of amounts.

Glycerine: Humectant, and used as a solvent when you make plant extracts. Cosmetics have a lot of extracts, so they may use this as a solvent. Also used when you make transparent soap. And boosts the preservative effect. Glycerine is a preservative like sugar, but you have to use it a lot of amounts. I mean, A LOT OF.

Propylene Glycol: Somehow, Lush loves this ingredient. It’s also like glycerine, but this feels more synthetic. I tend to use glycerine in my cosmetics and extracts. Also, this ingredient heavily used as a solvent of aroma chemicals.

Xylitol: Used in toothpaste as bacteria killer and sweetener. I love this ingredient so much. You can even make a candy that cleans your teeth with this.

Isopropyl alcohol: Never used this, but B&BW uses this in their body scrubs. I think it has some “scrubbing” properties.

Was about to say someone forgot their phone going to the bathroom. Remember when we didn’t have cell phones and you would read just about anything you could reach.

if you want to know how they’re chemically different, skip this. If you want to know why they’re different but still called alcohol, give this a try.
You’re letting labels and your unfamiliarity with chemistry intimidate you. If these were soft drinks, which you probably have a lot of experience with, you could easily understand the differences. You can probably explain the difference between Coca-Cola, lemonade, Slurpee, tea, and seltzer. They’re all pretty similar, but made slightly different ways. Some are better in certain situations.
Same difference with the alcohols.

There is no way of ELI5-ing alcohols. This is some seriously complicated organic chemistry (organic since it’s molecules built up from the same type of atoms that you find in plants&animals. Just often arranged very differently) and there are thousands of different types of alcohols.

However, when looking at shower gels they do two things (mostly).

1. They keep everything together and looking non-icky.. The shower gel looks like a single liquid instead of letting stuff pool at the bottom or floating on top or becoming flakes floating around in the gel.
2. They change how it feels when you touch it. Companies spend a lot of money to have shower gel feel exactly right (the right amount of squish, clinginess and goopiness), and a big reason for showergels feeling like they do is what kind of alcohols (and how much of them) you put in it.

Most of the time the alcohols are used to build viscosity and provide “structure” to the formula. Cosmetic Scientist

Where does isopropyl alcohol fall on this list? I’m in the military and we use it a lot in regards to aircraft maintenance.

I don’t see it in any top-level comment, so… in chemistry, “alcohol” just means a molecule has an -OH (hydroxyl) group. That’s an oxygen atom bonded to a hydrogen atom, and essentially those can travel together as a pair and attach to others things. It imparts some polarity (to small molecules especially) and can make a compound more soluble in water.

You can of course have multiple OH functional groups attached to a single molecule. Two is called a diol or 2-ol. There’s also triol (3-ol) but you don’t hear that outside scientific contexts. You can keep going with tetrol, pentol, and other Greek prefixes, or “poly-ol” more generally. You may even see the OH group named first, as hydroxy-(something). But not everything with hydroxls ends in “ol” (as others said, sugars like glucose). Some names are historical or come from biology instead.

Anyway, the differences in “alcohol” compounds you see in your toiletry products is, well… everything about their structures beyond the OH group!

While we’re on this topic, is it okay that I just wash my hair with bar soap?

Why do some bodywashes dry my skin and make me itch. For example the cream ones like Nivea and dove make me itch, but Irish spring original scent body wash does not…. I narrowed it down to 2 ingredients metalozione (sp*) and another… But recently others that don’t contain those 2 ingredients still make me itch

These are usually surfactants if it’s a shampoo you’re looking at. Surfactants are the molecules that soak up grease and dirt and are found detergents. They are much different from the alcohol that you know and love.

They are alcohol ethoxylates which is a fancy way of describing a molecule which one side is a type of oily alcohol (fatty alcohol) which repels water but likes oils, fats and grease, and the other side a water loving bunch of carbons and oxygens stretched into a long chain. When this is put into water, the water repelling side attracts grease, oils and dirt, and the water loving side helps to suspend what the other half has picked up in the water, meaning you can now rinse and wash away whatever you were trying to clean. Without the alcohol ethoxylate the grease and oil wouldn’t mix with the water and it wouldn’t move. If you’ve ever had hair wax and tried to wash it out with just water you’d know what an awful mess it makes.

The ‘alcohol’ really only describes the functional group of a part of the molecule. You’d poison yourself quite badly, and you’d never get drunk on it. If you tried to substitute it for your favourite whiskey.

Alcohols have the structure R-OH. It’s the R that differs. There’s almost no limit to what R can be.
The OH tends to make the compound more water friendly, but can be overwhelmed by a fatty R.

The simple answer is, the difference between the alcohols is their chemical structure. In chemistry, there is a formal naming process of molecules (IUPAC), but often for chemicals that are more prevalent in use there is a different “common name”, especially if the IUPAC name is really long or that name looks scary to a consumer. Do you want to read lauryl alcohol or 1-dodecanol. In products for bathing, the various alcohols listed are really very similar, the main difference is the carbon chain attached. Think of the alcohol having a longer tail, shorter tail or fluffier tail. The reason why these compounds are put in these type of products is because the, -OH, alcohol part of the molecule is similar to water in the way it behaves, meaning water can rinse it out.

To add to what everyone said almost everything which names end with -ol it’s technically alcohol, even cholesterol

It’s simple. An alcohol is a carbon chain (CH-)that ends with an hydroxyl group (-OH). Ethyl alcohol (or ethanol aka drinking alcohol) has a carbon chain length of 2. The alcohols used in a lotion or conditioner are called fatty alcohols because they have a long carbon chain. Cetyl alcohol has a carbon chain length of 16. Stearyl alcohol is 18. Behenyl is 22. The higher in carbon chain length you go, the “heavier” the molecule and “fattier” it is. Thats why ethanol is a liquid (its lighter) with a carbon chain length of 2 and cetyl alcohol is solid wax with a chain length of 16.

Source – Cosmetic Chemist

Sorry to piggyback on this thread, but I also notice most shampoo/gel/conditioners have “aqua” listed as an ingredient.

What makes this different to water?

Not everything can be dissolved in water. Some things need to be dissolved in alcohol or oil before they can be mixed together to make a shampoo.