Personal lubricant
Personal lubes
You can broadly categorize personal lubes into oil-based, silicone-based, and water-based.
Oil is the simplest, but doesn't like latex - condoms or otherwise.
Silicone is also fairly simple, but interacts with silicone materials.
Water is largely some thickener plus water
Silicone and water based lubes are often formulated a little more specifically to be safe inside you,
though some standards could stand to be a little stricter.
Water based personal lube
Water-based lubes have become common and popular because they are pretty neutral and therefore safe to most groins and pretty much all sex toys.
One drawback is that at least the the water in them will evaporate more quickly, so if you're planning on long sessions, have a glass of water, or tongue, or the lube bottle, on standby.
Water based lubes seem to mostly be a combination of one or two glycols and water to thin it out.
Some water based lubes are relatively odorless and tasteless, others not so much. You may care about that when you're switching positions a lot, going back to oral, and such.
Depending a little on ingredients, water-based lube is less likely to leave stains.
Water itself isn't a useful lubricant for more than a few seconds, though this can sometimes be useful.
When you want to try to avoid a tickler going straight to the base of your cock where it won't do much good, you could put it in place with water, after which the friction should return and it should stay put for a while.
Silicone based personal lube
Silicone-based works well with partners and condoms, so person-on-person this is a very practical lube, and it sticks around longer than water based lubes.
It's also good with a bunch of sex toys, except of silicone toys, and you should assume that includes cyberskin-like materials until you know they are fine.
Since silicon toys are often a little nicer and a little more expensive, you will probably know when you have them and whether to avoid silicone lube.
Oil as lube and/or for massage
The most viscious lubes will often be lipids - oils[1].
Avoid oil if you have latex condoms
- It will render condoms ineffective even if they don't seem to visibly break
On top of that:
- Not all oil is created equal.
- Not all sex shop oil is created equal either
- In general, if you can eat it, it's safe enough on you, though possibly an irritant in you
- If you don't want to think about the details, limit such oils to massages.
- Assume oil will break down silicone, jelly, cyberskin, and some other toy materials
- often not instantly, but they'll wear a lot faster
- It's enough of an issue that you may not want to use oil except where you know it won't do this, or where you know to clean up.
How long oil lasts in the act varies, but is generally longer than most non-oil lubes, which can be an upside or downside depending on what toys you want to use, how long your sessions last, and how quickly you want to be presentable elsewhere.
Silicon lubes may be a good second here. Note that products called "Silicon oil" is typically just silicon, and not oil in the chemical sense, just in the 'is slippery' sense.
- relevant in that silicon is compatible with latex, oil is not.
- there are some myths around that they are latex-unsafe, probably because of the word 'oil'
- (...though silicon is still incompatible with silicon toys)
Preferred properties
On osmolality
Roughly speaking, osmolality measures amount of something dissolved in water (or another solvent), to estimate the amount of osmotic pressure - differences in osmolality causes moving water into or out of cells (because osmosis).
In this case, many lubes have a rather higher osmolality compared to the vagina, which means that it will dry out tissue (because osmosis).
It's not a strong effect to bother a lot of people, but if you are sensitive to this, this is one reason you may find some water based lubes to be much more comfortable (they'll be the ones with lower osmolality).
Also, that high osmolality seems to comes largely from
the things that make the lube slippery, and
the things that preserve it longer.
Note that you may have an easier time finding a silicon lube that fits you. Silicon is itself slippery and does not need preservatives, there are fewer additives to be potential bother.
On pH
A vagina is happiest with a pH somewhere around the range of 3.5 to 4.5, on the acidic side, so that it can regulate its microbiome, and avoid things like bacterial vaginosis.
Many lubes aim for a pH around 4.5, or technically have no pH because they have no water, so this is generally not an issue.
Additives
A few ingredients have some footnotes to them.
Glycerol/glycerin in lube
Nonoxynol-9
Nonoxynol-9 is used in some condoms, being useful as a lubricant (and as a mild spermicide, though not very effective at that in the quantities used on condoms).
It breaks down fat (arguably a detergent), which may irritate sensitive skin and the vagina, particularly the cervix, and also the anus.
The fact that it dries out skin somewhat, while not a direct problem, doesn't help.
So if you have a problem with irritation, experiment with different lubes and different condoms to see what the cause is.
See also:
On stains
Generally, oil is most likely to stain sheets.
Water-based the least likely.
Silicon is often fine, and if it stains it can often still washes out fine - though following some specific instructions may help the results.
- Apparently washing it earlier is gives better results
- apparently there are some ways to accidentally make it worse.(verify)