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Glycerin use in intimate lubes and moisturisers

June 30, 2018


There, if that word is a problem for you then best to switch off now as that’s what this is all about.

map of tasmania

Aussie slang for a ladies privates 😉

Ok so the question of whether glycerin is OK or not to have as an ingredient in products heading for the vagina came up recently and I just had to investigate.  It came up because one only needs do a quick ‘google’ to find conflicting information on this topic – some Doctors say it’s Ok, some say it’s not, some brands say likewise as do some bloggers,  health ‘news’ sites and so on and so forth.  As with most areas of conflict the hard evidence of facts seem to feature less prominently in the discussion as momentum grows,  like you don’t really need an anchor when your audience is already primed to accept one outcome or another.  That isn’t scientific though and that kind of discussion doesn’t impress me much hence the need for this brain dump.  So here goes.


Chemically glycerin is a polyol and polyols have alcohol functional groups.  It wouldn’t be right to say that glycerin is an alcohol in the same way that ethanol (drinkable) alcohol is although it does share some features.  It is water-soluble, has -OH functional groups (that’s the alcohol part) and is a decent solvent (but nowhere near as strong as alcohol) but that’s pretty much it.  Unlike ethanol, glycerin (or glycerol which is its other name) is a moisture binding active.  It likes to suck water into its self, holding onto it like a greedy little squirrel hoarding its nuts for the winter, never to let go….  Oh sorry, back on track.  But it can and does let go.  Glycerin is a humectant and humectants bind moisture via osmosis so if the concentration of water is high in the surrounding tissue they may suck some out of that tissue until they are in balance but if the surrounding tissue is dry, they will release some moisture into it, again to balance it out – in that way you could say that glycerin is a very considerate water carrier and is a good sharer.  How this plays out in skin care is that for the most part, that the water content of glycerin is higher than the water content of the skin and in balance with the atmosphere (sort of) and so moisture is pumped onto and into the stratum corneum leaving a balance and no negative effects.  If, however, the atmosphere is super dry, the glycerin could try sucking moisture from the skin, especially as skin cells typically have around 60-70% water in them, this can lead to the awkward position of the glycerin-containing moisturiser leaving the skin feeling very dry.  In opposite situations where the weather is very wet, such as in a tropical location or during monsoon season, the glycerin hits super-saturated skin and ends up just leaving the wearer feeling sticky and gross.  These nuances can be formulated around so that glycerin can be used in all cases ON the skin but what about IN the body?  We’ll get to that in a moment.

Glycerin its self is quite a safe ingredient as far as the skin goes and it hardly ever causes any problems because of its chemistry although that doesn’t mean it’s problem free.   I mentioned above that glycerin has some solvency properties.  If it didn’t, you’d not find it used as a solvent for herbal extracts, the ingredients we call glycerites. In a glycerite the glycerin is being used as a medium into which the phytochemical from the botanical matter are extracted. This pulling power or solvency is what can cause issues on the skin as to be a solvent you have, by definition, the capacity to dissolve things (not all things but some things) so glycerin could, at some point and under some conditions, dissolve chemicals that are naturally occurring on the skin, thus affecting its natural balance.   But before we start to contemplate the damage that glycerin could potentially do in its role of solvent, it is worth remembering that water is also a solvent and that we recognise that if we spend too long in the bath the water can dissolve our skin lipids and leave our skin super dry – weird but true – I suspect from glycerins chemistry and what has been written scientifically about glycerin that its solvency power is going to be in that order with regards to skin consequences and that the glycerin would most likely have to be used in an un-balanced way for it to start causing that type of problem.  So, to my mind any down side with glycerin is going to be less about its solvency and more about something else, probably its osmolality.

As I mentioned above, glycerin carries and delivers water via osmosis.  This, to me, looks like being its number one super power in terms of Lubrication and Vaginal health as well as the thing most likely to cause problems if there are any.  The vagina is a muscular tube protected by a mucous membrane which is made up of cells called a stratified squamous epithelium. This structure is the same as the cell layer found in mouth but nothing like the skin that we present to the world on our face.  Facial skin is covered in a dead layer of keratinocyte that acts like a flexible coat of armour that’s hard and water-resistant.  Our Vaginas on the other hand have live skin cells on their surface and are, in stead, protected by a mucosa which protects the soft tissue underneath.  Mucosa has to be moist to be healthy – terrible analogy but think of a slug, without their slime production ability they would just be looking all dried up and prune-like,  or like a discarded fake eyebrow – not good.  So, it doesn’t take much brain power to work out that a balanced, healthy vagina is one which has a happy, healthy mucosa and a happy mucosa should have just the right amount of water – not too much and not too little.

Is there a way of telling if a product is balanced properly for the vagina then, with regards to moisture levels?

Fortunately there is.  Osmolality can be measured in a lab so a lubricant or intimate moisturiser can be sent off and analysed for a small(ish) fee taking all the guess-work out of life and giving us at least one answer to our question about whether glycerin should be avoided in our vaginas.

So, we know the Osmolality of a healthy vagina and we can test the Osmolality of our products so the potential for an ingredient to over-dose the vagina with moisture or suck its moisture layer dry can be mitigated with some simple analytical chemistry and a bit of formulating know how.  How very simple…

Osmolality = measure of the osmoles of solvent in a Kg of solvent.  Osmolarity = measure of the osmoles of solvent in a Litre of solvent.

The molecular weight of a solute, in grams, divided by the number of ions or particles into which it dissociates in solution.

So if it’s that simple, why are we still debating it?

Well there seems to me to be a few things at play here, opportunity could be one of them.

Glycerin free is a mini-trend in this area thanks to one or two brands cottoning on to this osmolality malarkey early.  Glycerin is a key component of the most dominant brand on the market, KY Jelly (in terms of lubricants) so one could come to the conclusion of what better way to carve out your piece of the pie than dis the competition, especially when there’s a shred of plausibility to your position and especially when it looks like anyone opposing this will have difficulty in proving the opposite i.e that there is no issue with glycerin in these products.

From the description of Osmolality above, fellow chemists of the world will spot that Osmolality is going to be pH dependent and concentration dependent (how MUCH of an ingredient is present) so it is highly likely that a products osmolality is influenced by more than just glycerin and further, influenced by more than just humectants. So if humectants are just one part of the puzzle why is it that that’s all we are talking about?   To put this another way,  it would be easy to avoid glycerin and still have an Osmotically inappropriate solution on our hands.    Here are some other ingredients that influence a products osmolality:

Amino Acids.


Simple Sugars (sucrose, xylose, glucose, etc)

Inorganic Ions such as salts (electrolytes)- Sodium Lactate, Sodium Chloride, Potassium Chloride, Sodium PCA. 

Carbohydrates (could be soluble or insoluble fibre types if using ‘foody’ language.

And here is a pretty good definition of what Osmolality is. Osmolality factors greatly in developing formulating for tube feeding and other pre-packaged meal replacements such as baby formula or adult food supplements/ meal replacements.

Further, this study found that combining osmolites changes the water flux of a formula so while Osmolality is a good measure of the strength and potential of a solution to change the water balance of a environment, it isn’t the only measure.

As an aside:

It is pretty interesting looking at the non-glycerin formulations out there now as I’m yet to find one that doesn’t include other osmolites in their formula and that doesn’t surprise me because osmolites are what NEED to be in these formulations.  So it is likely that it’s not about avoiding all or any one ingredient that changes the osmolality of a liquid, it’s about appreciating how to balance them for best results and tolerability, including water flux.  That’s science, the rest is marketing.

The vagina fights back.

Anyone with a healthcare background will also appreciate that the body is not passive – the action isn’t all a one-way-street.  What I mean by this is that even if the Osmolality, pH and water flux is right, that’s only part of the story in terms of vaginal compatibility.  The vagina might react to the lubricant or moisturiser because something else is triggering a reaction such as an aromatic material, a preservative, a plant extract or an oil.  These things might still induce stress on the area.  Again this type of thing is not often discussed and I do have my suspicions about why but this might just be my own bias talking.  What I think plays a part in keeping this detail quiet is creative and expressive freedom.  It’s pretty bloody boring and mind-blowingly complex to admit that any one of your ingredients can trigger a vaginal meltdown so it’s best to just focus on what one thing, ‘solve’ that then hope nobody has an issue with what’s left.  Also it does allow for brands to use their own special magic sparkles to liven up their product offering – adding essential oils, herbal extracts and so on and so forth.  Also, it gets very expensive to test each component of a formula for its safety and irritation potential in a particular area and if you test your whole formula and find it wanting it’s hard to then go back and fathom what made the thing not work.

So are we there yet or is there anything else?

Look, to be honest there is something else that might be festering in the back of some people’s minds about glycerin but only if they’ve done a lot of reading…

Glycerin has been found in decent amounts around surgical implants and implanted devices that have developed a biofilm of Candida albicans.  It is not suspected that the glycerin CAUSED the biofilm, more likely the glycerin is a metabolic (made in the body) bi-product of the dysfunction.

If there’s one thing that ladies don’t want to encourage it’s the old Yoghurt pants and so you only have to mention the remote possibility of that for women to run in the opposite direction and I understand that, I really do only these things aren’t necessarily related.  The biofilms being discussed here are typically on implanted devices within the body in general and the glycerin found is not injected as a product or rubbed in, it’s manufactured by the body as a consequence of the dysfunction that’s already happening because of another set of circumstances.  Now I’m not qualified to say whether this is never going to be an issue worth thinking about for vaginal lubricants but I’d say it’s highly unlikely to be relevant, even for women who have vaginal mesh implants to correct prolapse or other issues, not least because there is little chance of any product you apply to that area will end up passing up and into the place where an implant might be sitting and even if it did, avoiding glycerin in a product wouldn’t solve the problem when the body can clearly make its own anyway.

Here is an article explaining this. 

And is there any truth to the worry that glycerin is a sugar and sugar leads to candida?

Glycerin is a sugar alcohol and oddly enough it is not classified as a sugar OR an alcohol which is confusing. Instead it’s a polyol.  Sugar alcohols exist naturally in fruits and veggies and if you’ve ever been on the low FODMAP diet you’ll know all about that food group. So if we want to ban glycerin from our vaginas because its too sugary, we’d also need to consider banning extracts of mushrooms (unlikely to be present in a sex lube but you never know, people are weird)  avocado, apple, apricot, watermelon, nectarine or pear extract too.

It was when I was ‘googling’ this that I found the above, so I think that might be where the initial hysteria came from but it’s still worth a deeper look.  There seems to be discussions within the Candida support network about glycerin and xylitol and other alternative sweeteners that might be used while on a Candida management diet. These forums seem to focus on the qualities of the ingredients when ingested rather than when used on the skin and even then the rational for the conclusions given leaves me feeling a bit like nobody really knows what they’re talking about to be honest.  Glycerin is sweet and can be used as a low glycemic sweetener for food although that’s not its primary purpose in food as it is actually not that sweet and packs more calories than sugar. But because it has a low glycemic index it is popular with diabetics in the same way that sorbitol is (glycerol and sorbitol are similar but different of course).  Here’s a sugar comparison table. 

The idea that putting sugary (or sweet) things ON the skin can cause a yeast infection in the same way that eating a high sugar diet can upset your micro biome is interesting but unlikely to be scientifically accurate, not least because people making the link neglect to investigate IF, WHEN, WHY and HOW high sugar diets alter the biome, whether they do that alone or when other dietary deficiencies or pre-existing conditions are present and whether that dysfunction could even happen on (or in) the skin.  Here is a link to the candida sugar diet tips. 

This sort of situation is very annoying for a cosmetic chemist as again, it provides a doubt in the mind of the general public who, not having time or the energy to really think about it decide to make a quick decision not to risk it (the precautionary principal that plays right into the conservative nature of the human psyche) thus eliminating any possibility of intellectual dialogue.

All I would say is that if the sugariness of glycerin has the potential to cause a problem then so does the sugariness of

So what’s the conclusion then?

Based on the research that I’ve done for this article and over the last year for other projects I’ve worked on I have found enough evidence for me to conclude that avoiding glycerin is not necessary and further, the idea that avoiding glycerin is the ONLY step needed to ensure the resulting product will be good is ridiculously un-scientific. Like many things that come up about cosmetic and personal care ingredients, this ‘free from glycerin’ type of claim has the potential to spread in popularity because its simple and because there’s a shred of truth behind the fact that too much glycerin can be bad, but as I said above, so can too much salt, too much amino acid, too much ANYTHING GOOD practically.

With my science head on I’d back glycerin as a good, low-potential for irritation, cost-effective, environmentally friendly, bio-compatible humectant for vaginal products against its alternatives, especially given its long history of relatively safe use in this area even in spite of KY Jelly not getting its Osmolality spot on, clearly the vagina can cope with that, of course it can, it’s part of a woman 🙂

With my brand owner perspective head on I’d be honest and say ‘yep, the glycerin thing could become a bit of a shit fight but the science doesn’t stack up to discount it on those grounds so you would be discounting it on marketing terms.  If your brand is a marketing heavy type brand then fair enough, take out or leave out glycerin but if you are selling yourself scientifically be careful not to over-hype the ‘glycerin free’ claim as it has no scientific basis.  Overall I’d love to think that brand owners can stand in their power and stand up for real science but I understand that marketing is often more powerful in terms of influence, income and business success. That’s a shame.

With my vagina owning head on I’d be looking out for products that discuss things like the product pH (that’s important) and it’s osmolality (very important). I’d personally be turned off crazy ‘free from’ claims but do accept that that’s probably because of my chemistry background.

So that’s it really.  I can’t see any reason why the average lady can’t use a lube or moisturiser with a bit of glycerin in it as long as it’s been formulated with vaggie health in mind and I don’t care what individual doctors say because it’s a little known fact that you don’t need to be a pharmacist, compounding chemist or cosmetic chemist to become a doctor or even a gyenacologist and while it’s true, these people are clever, they can’t possibly know everything and maybe sometimes, they don’t even want to.



2 Comments leave one →
  1. July 1, 2018 7:58 pm

    “dried up and prune-like, or like a discarded fake eyebrow” BWHAHAHAAHAHAHAHA!!! I love your writing style! I had coffee coming out of my nose this morning!
    Thank you so much for this article! I have been running away from glycerine, maybe it is time to give glycerine based lubes a second chance!

    • RealizeBeautyEd permalink*
      July 1, 2018 8:59 pm

      Lol well you know what they say, if you don’t laugh you cry 🙂

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