I hope someone can offer me good advice on this, it's driving me nuts. It's been going on for about a year, every once in a while (two months or so) after having sex my boyfriend gets thrush on his penis, but I have never had any symptoms. The only thing i've had is cystitis and I know for sure that it's only that because I always go to the doctor to get it checked out and get antibiotics. I want to know what I can do to prevent this happening to my boyfriend...If I do use thrush treatment, when do I use it? I mean, doesn't thrush come and go, and if I have it, why do I not have symptoms?