I've no idea on the cause I'm afraid, I suppose friction can aggravate them though!I use a hot compress and the majority of the time it all comes out. Sometimes I squeeze them although I'm sure that's probably not the best thing to do. I've read they can need lancing if they get big but mine never had fortunately. Can anybody pin point what causes them? This sounds a bit gross but I'm sure semen aggravates me - sorry TMI
To be fair I haven't had one for a few months now. There never seems to be a pattern of when I get them.