When I started selling lube over a decade ago, sex-shop-sex-educators were talking a lot about glycerin. That’s because lots of people were coming to us complaining of yeast infections after using lube containing glycerin, and there was no denying the large number of relieved vaginas after switching to a glycerin-free alternative.
What we know now that we didn’t know then
Because of these widespread experiences, the general theory was that glycerin, which is a sugar alcohol, could feed Candida like plain old sugar does. But we now know that this isn’t how sugar alcohols work. Rather, glycerin can lead to infection because it can cause a lube to pull moisture from the mucus membranes, essentially dehydrating the cells and tissues of the vagina or rectum.
In scientific terms, glycerin can affect what’s known as the “osmolality” of a lube, which basically just refers to how concentrated a lubricant’s ingredients are relative to its water content. Glycerin’s densely concentrated nature causes some lubes to be super concentrated (or in scientific parlance, “hyperosmolar”).
Studies have shown that, in addition to contributing to tissue irritation and dryness, very concentrated lubricants put people at greater risk of vaginal infections, like yeast overgrowth or bacterial vaginosis, as well as STIs.
For those of you who are interested, here are some of those studies: Wilkinson et al., 2019; Ayehunie et al., 2018; Dezzutti et al., 2012; Adriaens & Remon, 2008; Fuchs et al., 2007.
Why put glycerin in lube anyway?
Glycerin, also called glycerol, is a clear, slightly sweet-tasting, thick, slippery liquid. It occurs naturally in plants and animal fat, or it can be synthetically manufactured.
It’s used in lube because it enables water-based lube to stay wetter for longer, by preventing it from evaporating too quickly (once the water does dry up, however, glycerin-based lubes tend to be pretty sticky).
Is it better to just avoid lubes with glycerin altogether?
Glycerin in and of itself isn’t really the problem. The thing you need to be concerned about is the effect that it might have on a lube’s osmolality (and potentially also on its pH levels, since glycerin has a higher pH than most vaginas).
According to writer and lube educator Rebecca Pinette-Dorin, author of this very informative defense of glycerin, it might come down to the type of glycerin being used in a given lubricant, with vegan medical grade glycerin less likely to cause problems compared to food-grade glycerin derived from animal fat. Sadly, though, companies rarely declare where their ingredients come from, so you won’t necessarily know which type they’re using.
Ultimately, if a lube containing glycerin isn’t too concentrated and matches your ideal pH range, then there’s probably no big cause for concern.
Which lubes are safer?
Lubes with a safer pH range will depend on where you’re using the lube and what’s normal and healthy for your body. This blog by The Fornix is a good place to start learning about pH and my own post about lube pH is coming soon!
Regarding optimal osmolality, make sure to check out my post “How infection is connected to your lube’s concentration levels”. In short, the least problematic options are iso-osmolar lubes, measuring in at around 250-300 mOsmo/kg, as these won’t interact with the water of your cells at all. That said, slightly concentrated or diluted lubes often don’t cause issues either, so if you want to expand your options while still remaining in a relatively safe zone, then look for lubes with an osmolality approximately between 150-380 mOsmo/kg.
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