Diet, hormones, drugs. Anything one ingests can manifest in an odor. Also you being the observer of said phenom may be more sensitive in this particular sensing ability. Also women generally are more sensitive to men's odor & men to women aroma. (They shold talk about us? Have you been to a men's lavatory? Blech)

I had to have my upper jaw repaired. As a result, they moved the entire thing 13mm forward. They also had to remove the back of the roof of my mouth. So, in addition to no gag (and never being able to eat in a reclined position again) something was uncovered and now I smell EVERYTHING. If anyone ever offers this to you, decline. I can smell when a woman has her menses, and I can smell any infection long before it's an issue. (My vet thought I was way too close with my cat)
Men smell different to me. And gay men not only smell different (and so much better than) from straight men, but different within the ranks of masculinity. It is all very subtle. I never wanted to know any of it.(mold is an all-consuming smell. I have removed most cloth items from my house because they retain it and people's breath, unless they have a respiratory or tooth infection, or cancer, is no longer a "bad" smell)
But men's cologne, especially musk cologne, smells like ass. Really. Need cologne? Rub a citrus rind behind your ears.