Lube Safety Basics

Things I learned about lube
2025-04-15 / Kirstin Rohwer / CC BY-SA 4.0 / sex, education, fediverse, en

This text is a lightly edited copy of a thread I originally posted on my private Mastodon account in october 2023. The server on which that account was hosted has recently shut down, and therefore all my posts have gone down with it.

So when someone asked me for a link to “the lube thread”, the easiest way to make it available again was to dig through an archive of that account and re-publish the text on my own website.

Disclaimer: Please note that this is just a summary of things I had read back then from various sources. I haven’t fact-checked all the details, and I’m not a scientific expert on any of these things. Some the most helpful sources are linked in the text, read them yourself if you want to make sure I didn’t misunderstand them.

Introduction

I’ve been reading a lot about sexual lubricants in the last few days, and I’ll share my learnings with you in this thread - because it seems that most people have never even heard of the most common lube safety issues, and a lot of unsafe lubes are sold everywhere.

Basically, there’s four different kinds of lube that are sold for sexual stuff:

Each of them has specific safety issues that are good to know about, so you don’t hurt your skin and don’t destroy your toys, condoms, etc.

Oil-based lubes

Oil-based lubes can be made from a mix of different oils. They should be plant-based - mineral/petroleum oils (like vaseline) are not recommended. Coconut oil (the high quality organic, virgin version used for food) seems to be popular as a kind of DIY version.

Oil-based lube doesn’t dry out, stays slippery for a long time and is often recommended for anal use and handjobs. Oils are generally safe to use on silicone toys (e.g. butt plugs), but can be a bit tedious to clean off of them.

What to watch out for:

Silicone lubes

Silicone lubes are very simple and often have less than five ingredients - the main one is usually “dimethicone”. They don’t dry out, feel less greasy than oil, stay slippery for a long time, and a small amount goes a long way. They’re safe for both anal and vaginal use.

What to watch out for:

Hybrid lubes

They’re mostly water-based lubes with a little bit (less than 10%) of silicone mixed in. They tend to dry out less quickly than pure water-based lubes, but avoid most problems of pure silicone lubes by only having a small amount of silicone.

Hybrid lubes are the newest invention of the lube industry, and there hasn’t been much specific research into their safety.

It’s probably useful to watch out for the same things as with water-based lubes in general (pH, osmolality, and potentially irritating ingredients - more on that later), and do a patch test before using them with a silicone toy.

Water-based lubes

The vast majority of lubes that you can buy are water-based. Water-based lubes are compatible with all kinds of toys and condoms, and they feel most similar to the natural fluids produced in human genitals. Good water-based lubes are safe for vaginal or anal use - but don’t use the same one for both (see the part about pH for a reason why).

There are three main issues to consider when looking for a safe water-based lube:

I’ll explain more about each of them in the following parts.

pH

Vaginas have a pH between 3.5 and 7 - depending on menstrual cycle, age, and if there are any infections. A pH between 3.8 and 4.5 is considered most healthy, so that’s what a lube for vaginal use should ideally also have. If your pH is usually a bit higher (e.g. in post-menopausal vaginas), a lube with pH around 4 can even help decrease vaginal dryness and infection risks.

To achieve the acidic pH for vaginal lubes, lactic acid is considered the best ingredient, because it also occurs naturally in the vaginal fluid.

Lubes that are ideal for vaginal use can be painful and damaging when used for anal! The rectum has a pH between 6 and 7, so a good anal lube should also be in that range.
PEO-based, powdered lubes that you mix with water are usually ok for anal, but not for vaginal use.

If the pH of a lube is not declared on the packaging, you can use pH test strips to analyze it yourself.

Osmolality

Osmolality (measured in mOsm/kg) describes how strongly something will try to pull water from its surroundings.

Human vaginal and rectal mucus have an osmolality around 285.
If a lube has much less, it can cause the vaginal/rectal skin to soak up water and eventually make some cells burst.
If lube has a much higher osmolality, it will pull water from the outer skin layers, which causes the cells to dry out and then be easily damaged or even peel off. Without these protective layers, the vagina/rectum is in much more danger of infections and other problems.

Ideally, lube should be in the range of 150 - 380, but between 50 and 450 is still considered mostly safe.

Sadly, most commercially avaliable water-based lubes have a much higher osmolality - well into the four digits O.o The WHO says that any lube above 1200 should definitely be avoided - and that’s already a compromise, because it’s actually still way too much.

Most lube manufacturers don’t declare the osmolality of their products anywhere.
Testing osmolality needs a lot more expensive equipment than testing pH, so it can’t be easily done at home. Therefore, we have to rely on other people’s reseach for finding a good lube.

There are some studies where specific lubes have been tested. If you’re in the US, you might find useful info in one of these lists:

But if you’re somwhere else, it might be hard to find anyone who sells the recommended products from those US-based lists.
(I live in Germany and I’m still looking for a local shop that sells brands like Good Clean Love or Sliquid. If you know about one, please tell me.)

So how can you know a lube’s osmolality, if there is no specific research about your locally available products?

You can’t be completely sure, but looking at the ingredients can at least help a bit. Most hyper-osmotic lubes (i.e. the ones to avoid) will have one of these among the first four ingredients:

Another thing to look at is consistency: the thicker a lube is, the more concentrated it tends to be (which usually also means higher osmolality) - how much depends on the type of thickener.

Every water-based lube has to use some kind of thickener and/or humectant - the concentration is what matters for safety, so any of these can be helpful in the right amount, but might be problematic if the lube contains too much of it:

Ingredients

In addition to osmolality and pH, there’s another area where lubes can be unsafe: toxic or irritating ingredients. Most of them are stabilizers or preservatives - used to keep the lube from going bad, but can also harm the vaginal/rectal microbiome, disrupt the body’s estrogen balance, or cause allergies.

This list is definitely incomplete, but here’s some of the worst offenders to watch out for:

For a longer list and some explanations, check out this blog post:
Personal Lubricant Ingredients Lists: Be Aware (phallophilereviews.com)

And in general, don’t buy any lube that doesn’t list its ingredients (apparently that’s a thing in the US).

Comments?

Toot to @flauschzelle@chaos.social or e-mail me at mail@metakiki.net.
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