>>345789I'm guessing you'd have to wash the bottle with soap after it holds anything other than water. I've never put soap on or inside mine. It will get dirty on the outside, so I just rinse it off about once every other month. I just looked inside mine and there's no mold or anything. But there is a sort of dusty film or something on the inside surface and it doesn't go away with water. You can see it in this picture where I wiped my finger across it. I don't know what it is, but it hasn't killed me yet.
