Honestly, this is the second mooncup I've set alight.
I sterilise it every now and then in between uses by boiling it in a saucepan of water. Today I went out leaving it on the hob and when I got back it was smoking away. The saucepan is ruined, but I suppose at least the house isn't on fire and I haven't had to have embarrassing conversations with firemen and insurance assessors...