A lot of people really enjoy anal stimulation. It makes sense: the whole area around the anus is extremely rich in nerve endings and is very very sensitive to touch. And really, as long as you wash regularly, it's not likely to be dirty or messy or any of those things.
A couple of things to keep in mind: because of the possible presence of fecal bacteria in the anal area, you should never go from anal stimulation or penetration to vaginal stimulation/penetration without washing your hands, penis, and/or toy well first, and preferably also using a fresh latex barrier (glove for hands/fingers, condoms for penises and toys). It's very easy for someone to get a vaginal infection because of fecal bacteria getting into the vagina or vulva, so do be careful of that.
Another thing to be careful about is lubrication. The anus does not produce its own lubrication. You need to use some sort of lubricant -- preferably water-based, and designed for sexual use, like Astroglide -- when you stimulate anyone's anus. The anus is made of fairly delicate tissue, more delicate than your penis or anyone's vagina or vulva, and is easy to damage. Lubrication will help you avoid damaging that tissue, and will also help things feel much better.
That said, a lot of folks do like anal stimulation and it's really perfectly normal and fine. Anal penetration is not *required* for anal stimulation (obviously!). There are lots of ways to stimulate the anal area without penetration. It's fine if the idea of being penetrated anally is arousing, but actually being penetrated there is not. That's normal too.
For more on your butt and anal sexual stimulation in general, read our article: http://www.scarleteen.com/pink/pages/ask_anal.html
What's true for anal stimulation and penetration is true for both men and women. Everybody has a butt. They're not different in different genders. Both men and women may enjoy anal stimulation, and that's just fine.
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