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How infection is connected to your lube’s concentration levels

Photo by Chris Liverani on Unsplash (speech bubbles added!)
Photo by Chris Liverani on Unsplash (speech bubbles added!)

If you're getting infections when you use lube, you're probably wondering what that's about. It could be something called osmolality.

Osmolality isn’t a thing most people have actually heard about. But if you use lube, you should definitely know a few things about it!

What is osmolality and why does it matter?

Osmolality basically just refers to the concentration of a solution or the amount of dissolved particles in a substance. In our case, that substance is lube.

The osmolality tells us how dense a lubricant’s ingredients are relative to its water content, which then becomes meaningful in relation to the cells of the vagina or rectum (specifically, the epithelial cells, which make up the top layer of the mucous membranes).

Very concentrated lubes are said to be hyper-osmolar, and more diluted lubes are hypo-osmolar. A lube that has the same osmolality as the epithelial cells is said to be iso-osmolar.

It’s worth noting that because the concentration of a lube’s non-water ingredients can only be measured in relation to its water content, osmolality isn’t a factor in lubes that don’t contain water (such as silicone- or oil-based lubes).  

Still with me? Don’t worry, the next part is still pretty straightforward. Because, unless you’re a scientist, there are just a few basic things you need to remember about osmolality when it comes to buying the right lube.

Hyper-, hypo-, or iso- osmolar lubes: which is best?

1. Hyper-osmolar lubes (very concentrated) are bad:

Very concentrated lubes pull water out of the vaginal or rectal lining, causing the top layer of cells to dehydrate. These cells are the body’s first defense against infection, so this damage can lead to an increased risk of STIs. It can also cause dryness, irritation, or burning sensations, as well a higher incidence of yeast infections and bacterial vaginosis. Lubes that contain very concentrated ingredients like glycerin, propylene glycol, or PEG are more likely to fall into the hyper-osmolar category.

2. Hypo-osmolar lubes (very diluted) aren’t great either:

When a lube has a higher water content than the body’s cells, the lube's water transfers to the cells, causing them to bloat. This doesn’t seem to have as severe consequences as lubes that dehydrate the cells – but it’s still not ideal and could lead to irritation or dryness.

3. Iso-osmolar lubes (matching or neutral) are the best:

This third category of water-based lube is the least likely to cause any problems, because it doesn’t disrupt the water content of the body’s cells. It is hands down the winner, especially for folks who are prone to tissue irritation or infections, are worried about STIs, or are trying to conceive.

How do I know the osmolality of my lube?

Frustratingly, with very few exceptions, lube brands still don’t generally include osmolality levels on their packaging or websites, even if they’re in the “good zone”. But, luckily, there are ways to find out.

Some scientific studies, like this one and this one, have published the osmolalities of several popular lube brands. Meanwhile, Women's Voices and Phallophile Reviews have both created helpful osmolality charts that include some of the smaller, less commercial brands.  

If you don’t see your lube listed in any of these places, I recommend reaching out to the company and asking.

Making sense of osmolality measurements

You’ll notice that osmolality is presented as a number followed by “mOsm/kg”, which is the unit measurement and stands for milliosmoles per kilogram. For example, the osmolality of Good Clean Love's Almost Naked lube has been measured at 270 mOsm/kg (the website offers a range measurement of 250-400 mOsm/kg). 

Here’s how to make sense of these numbers…

Following an expert review done in 2012, the World Health Organization recommended that people should avoid using lubricants with an osmolality over 380 mOsm/kg in order to minimize the risk of epithelial damage.

However, the report also acknowledged that most lubricants on the market had much higher osmolalities - anywhere from 6 to 27 times this recommended maximum measurement, and so for “sector procurement” reasons (i.e. to satisfy the needs of market capitalism) the WHO set their official recommendation much higher, at <1200 mOm/kg.

In the absence of any actual regulations, however, many popular lube brands continue to produce and sell lubes that measure well over even the WHO’s modified upper limit recommendation of 1200 mOm/kg.

Thankfully, the last decade has seen the production of several better lube options that do actually meet the WHO’s initial osmolality recommendation of <380 mOsm/Kg.

Fun osmolality fact

Osmolality is measured with an instrument called an osmometer. Just some extra fodder for a sexy scientist role-play!


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