Big community funding update! August 5, 7: NSFW and probably gross for most people I'm talking gay unprotected anal sex. Assume these are two consenting adults that are engaged in a monogamous relationship. Don't derail my question with cautions of Vaseline as lube for guys inherent risk of bareback sex.
It's extremely risky, don't do it!!!! Okay, lets move on. I know that popular opinion is against using this material for lube. It breaks down latex in toys and condoms and can linger a bit so it could break down condoms used in the next Vaseline as lube for guys days or so. I've heard that it can harbor bacteria which is a risk for infection -- however, I just learned that silicone lube does this also and I've used it for years without any problems.
I've also heard that it's used for actual medical purposes 'down there' without issue. I've done lots of googling, but I can only find info about how you're not supposed to use it for vaginal sex and the occasional cautionary tales of condom breakage. So, that leads me to the question - can I use vaseline as lube and not mess up my ass or the ass of my loved one?
Assume frequent usage times per week, and a good shower post-coitus. It'd be great to hear from someone that actually uses it regularly or perhaps has a friend or whatever. Vaseline is so messy. This stuff is fantastic. Good God, that is frequent use.
The least-bad consequence is that it wouldn't be very comfortable. Take away the direct contact with soap and water, and there you go. It's really really hard to wash off of skin and even harder to wash it off of hair.
Mucous cleans your rectum and colon.
Some people get lubricated several times a day. External cleansing is all that's necessary. Petroleum jelly can be difficult to clean from hairy areas. If you use a light oil, like olive oil, to clean the petroleum jelly off before washing with soap and water, you'll have better success.
Go Ask Alice is a pretty excellent site from Columbia University.
I didn't find anything specifically about petroleum jelly, but this tidbit of info about olive oil seems to apply: Just because olive oil is ineffective for use with latex does not mean you have to avoid using it in all cases. Although using a condom is always a good idea, monogamous partners who have tested negative for sexually transmitted infections STIs could decide to forgo a condom and use olive oil for lubricant.
However, even monogamous partners may think twice about an olive oil lubricant for other reasons. For some people, olive or any oil can clog the anal glands and follicles, which could lead to irritation and even fungal and bacterial infections. If you notice irritation after using any type of lube, it's probably a good idea to wash up well and switch to Vaseline as lube for guys. Here's the link posted by Stewriffic at 8: Um, er, let's just say if you use a lot it tends to get funky.