Nonoxynol 9
"This was and is still a  nightmare contraceptive.  Bought this and used with my boyfriend. Used 3 in one night.  We both had side effects.  We are exclusive if not. ..I would have thought I caught something.  Felt good after using but 2 hours later the excess is flowing out & leaves me feeling slightly irritated.  I wash again but still feel a persistent irritation. Day 2. he had a weird sensation while peeing.  Both of us have itchy genitals and it only gets worse from there.  I almost feel like a yeast infection.  My anal region itches.my vaginal area feels dry but it isn't.  It's just highly irritated.  I've used raw yogurt, acidophilus pulls and so feel irritated.  Never using this again. It's day 4 and these symptoms are still annoying"