What Is Lube Osmolality And Why Is It Important?

Osmolality is a strange word but is important for your vaginal and anal health because the wrong level can result in discomfort, cell damage, and infection.
Collage Of Glass Beakers Filled With Water And Solid Colorful Balls, Osmolality Concept

Osmolality is a strange word, but it’s one of the most important things to understand if you’re considering a water-based personal lubricant.

Lube osmolality impacts the way your vagina reacts to a lubricant. The wrong level of osmolality can result in vaginal discomfort, and cell damage, and has the potential to make your vagina and surrounding areas more susceptible to infection.

In this article we’ll look at what osmolality is, why it matters when it comes to choosing a lube, the World Health Organization (WHO) safety standards for lube osmolality, and how to find out your lube’s osmolality.

In this article, we’ll cover:

Editor’s Note: This article is part of our Everything Lube hub, an in-depth and evolving resource that comprehensively explores all aspects of personal lubricants from the different types and how to use them, to ingredients and safety — created to help you achieve the sexual pleasure you deserve.

What Is Lube Osmolality?

Maybe you’re thinking, “Osmo- what? This is lube…how much science do I need to know to use this stuff?”

The answer is some — especially if you want to keep your vagina or anus, healthy.

Osmolality refers to the concentration of particles in a solution. In water-based lubes, which are the only ones that have osmolality characteristics (unlike oil-based or silicone-based lubes), it refers to the amount of ingredients that are not water.

But it isn’t enough to just know the osmolality of a lube. You have to understand how it compares to the osmolality of the tissue it will come in contact with.

The osmolality of vaginal tissue is 285-295 mOsm/kg and the rectum is around 290 mOsm/kg.

Because the osmolality of both tissues is so similar, the osmolality of personal lubricants will affect each the same way.

If a vaginal or anal lube’s osmolality is higher than the tissue its being applied to, the lubricant is considered hyper-osmotic.

This can be bad because the vaginal or anal tissue will try to release its own water to the lubricant — the opposite thing you want happening with lube — and that loss of moisture can cause cell damage.

If the lubricant has a lower osmolality than the vaginal or anal tissue, it’s called hypo-osmotic.

Where a hyper-osmotic lube causes vaginal or anal tissue to release water to the lubricant, one that is hypo-osmotic reverses that exchange — those tissues will pull water from the lubricant.

In both cases, the difference in osmotic pressure between your body and the lubricant is like a tug of war, with water acting as the rope.

A personal lubricant that is in the same range as vaginal or anal tissue is called iso-osmotic, and that’s what you’re looking for in a lube.

A lubricant that is iso-osmotic has an osmotic pressure that is equal to that of the vaginal or rectal tissue it comes in contact with. There is no push or pull between them because the tissue and the lube have the same hydration level.

Do Anal Lubricants Have Osmolality?

Although osmolality only affects water-based lubricants, you may be wondering how much this concerns anal sex and rectal health.

As we mentioned earlier, the osmolality of anal tissue falls within the range of vaginal tissue, so a lubricant’s osmolality will affect both in a similar way.

Some water-based lubricants are suited to anal sex, although as we discuss in greater detail in this article, their pH level may not always be.

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Why Is The Osmolality Of Lube Important?

Your vaginal and rectal skin cells have a delicate moisture balance to maintain.

When they absorb water from a hypo-osmotic lube or release their water to a hyper-osmotic lubricant, that balance is disturbed — with the latter making your vagina or rectum more prone to infection.

According to one study, most lubricants are “strongly hyperosmolal.” Thus, research on hypo-osmotic lubes is limited and it isn’t clear how much of a danger they may potentially pose.

This is why iso-osmotic lubricants (those whose osmolality is about the same as your tissues) are important. They don’t change the amount of water that’s being held in the skin cells of your vagina or rectum.

Even if you’re not aware of osmolality, your skin definitely is!

If something has too high osmolality you’ll know right away from the burning, itching and dryness that ensues — and this applies to all tissue.

Hyper-osmotic reactions can occur in the vagina, on the penis, and in the anus.

When the tissue is compromised, it can make someone more susceptible to a range of infections including herpes, HIV, and bacterial infections.

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What Are The World Health Organization Safety Standards For Lube Osmolality?

Hopefully, you’re still reading this and not just throwing all your personal lubricants away!

Lubes can be great, and understanding the osmolality and pH of lubricants will help you choose a good one.

According to the World Health Organization (WHO), you want to choose a lube that has an osmolality of 380 mOsm/kg or lower, which means the very best water-based lubricants will have an osmolality below 380.

That said, the vast majority of personal lubricants on the market do not have an osmolality that falls within that range, so the WHO adopted an upper-limit recommendation of 1200 mOsm/kg or less.

For this reason, there is an important difference between lubricants that pass WHO standards and those that meet their recommendations.

Lubricants with an osmolality of 380 mOsm/kg or less are considered to pass WHO standards — as they fall within the safest osmolality range any product can have.

Personal lubes that meet WHO recommendations fall within the acceptable osmolality range of 381 to the organization’s upper limit of 1200 mOsm/kg.

Both are considered to be safe, but lubricants that pass WHO standards are the best and safest for your body.

How Can You Figure Out The Osmolality Of A Lube?

Do what we do for most things — check online!

But be aware, you may need to do some digging since osmolality is not always listed with every product (and in fact, some manufacturers don’t want you to know).

Instead, you may need to do a little research to see if a company talks about osmolality in general — that will give you an idea of whether or not their products fall into a good range.

You can also reach out to the manufacturer to specifically ask them about their osmolality. Some will be more forthcoming than others.

At this point, you may be asking “Isn’t osmolality testing for personal lubricants done by the FDA or some other agency?”

The answer is no.

There are plenty of lubes available right now whose osmolality is two to three times that of the vagina and yet they’re available for purchase — which is why it’s so important to know about this topic before you select a water-based lubricant.

If you want to skip the hassle and just find something safe and soothing for your body, you can review our list of the best water-based lubes.

In our thorough reviews, we specifically took into account factors like osmolality, pH levels, and of course, if the lubes performed in the bedroom.

One of our favorites is Aloe Cadabra. Made from all-natural ingredients, it has a body-safe osmolality of 172 mOsm/kg and a pH range of 3.8 to 4.2.

Not only that, but Aloe Cadabra openly discusses the importance of osmolality, so you know their products will be good for your vagina and rectum.

They’re so safe, in fact, that we reviewed them ourselves.

In Conclusion

Can all this science seem a bit boring?

Yes, but knowing what you’re putting into and on your most delicate parts, can help you to make good choices for the health of your vagina and rectum.