I usually boil it for 15 minutes or so before and after my cycle. I don't use any soaps or oils to clean it but I do use soap and warm water with it during my cycle (no anti-bacterial stuff, I absolutely HATE it).
Anyway, I have noticed a residue on my cup after boiling. I live in a rural area & we are on a well. Our water is clean but not as "treated" as water from city lines. I do notice whenever I boil water for anything, it leaves behind a residue on the pan. Could this residue be harmful? I have a pretty tough vag (I swear, it must be super resistant) and it hasn't been irritated yet, but I do have to wonder if it could pose a problem in the future
On another note, my boyfriend wondered why he hadn't seen any tampons or anything in the garbage (worrying that I wasn't getting my period) and when I told him he had a cup, he was extremely interested in the mechanisms of it. I gladly explained it to him, but as soon as I asked him if he wanted to see it, he immediately squirmed his way into the other room...oh well, maybe some day I can get him to love my Diva as much as I do. =D