Wait I'm so confused (non-Asian person here).  So if the argument is that women's underwear is unsanitary, then why not wash them in the washing machine on a separate cycle.. surely that would be more hygienic than handwashing (because much hotter water) than hand washing, yes?  Not that I think women's underwear is more unsanitary than men's.. just trying to figure out the logic here.  I know some people think it's gross to do kitchen towels in the same cycle as bath towels and underwear.  I think the hot water and detergent should take care of the bacteria but fine if you want to separate them yourself.   I can see if you have very delicate lingerie that you'd want to hand-wash to protect it but that's a separate thing from thinking that it has cooties that are going to contaminate the rest of your washing.