In this column: Does a guy’s mood synchronize with his girlfriend’s menstrual cycle? - The Straight Dope
…Cecil addresses the idea of men’s cycles synchronizing with the women their with (in the case of the question asker, he seemed to become more moody around his girlfriend’s time of the month).
As someone who’s spent the last two and a half years living with his girlfriend, I seem to have my own synchronicity with her cycle. And it’s not a moody thing, because she doesn’t get any extra moody, and neither do I. However, I find that the few days leading up to the beginning of her period, the amount of acne I have increases noticeably. (On a side note, I kind of wish at 36 my body would realize that it has long passed the age where I should still be having breakouts.)
I mean, this is certainly far from a scientifically controlled example, but it does seem that there is more to it than just a sympathetic reaction, at least in this admittedly anecdotal situation.
On a side note, when she was in high school she used to go on 40 day canoe trips through Canada. Apparently by the end of those a lot of the girls would be synced to her cycle. Maybe my gf is just one of those irresistible forces or something.