I only read about this recently, that it is advisable to not wear panties at night when sleeping. The reason I found for this is that wearing panties will encourage growth of yeast at the vulva area. However, I'm still not fully convinced. I mean, isn't more dangerous when you expose your vulva to the atmosphere all night long, open to all the bacteria in the air(or surrounding) or even the blanket and bed?
Bacteria is everywhere. Whether you wear panties or not. -shrugs-
I don't where undies to sleep. If I do, it's a pair of really baggy boxers. Let's air go through. ^_^ Wearing panties to sleep keeps your vagina in a little tight ball of fabric and it has no room to breathe or get fresh air. This makes hot air and hot stuff makes bacteria...That's how I learned it.
I think that you shouldn't wear panties to bed and shave every now and again to make sure you have no hair there that let's smells and other nasty stuff linger. Makes you semi-bacteria free. ^_^
...That sounded more childish than I wanted it to.