Is your girlfriend turned on or anything, by it?
I thought pheromones were
invisible chemical smells, in that you probably couldn't physically notice the smell? Moreso, just the
effect they have... BO then, is just some toxins and other crap coming out or around your sweat glands, which is the smell
Covering our body are around 3 million sweat glands. Most body odour comes from the armpits and groins, where the sweat is produced by glands called apocrine glands.
The sweat produced in these hairy areas is milk-like and rich in protein. Believe it or not sweat is actually odourless, but bacteria feast on this milky, protein-rich liquid producing the foul-smelling chemical compounds that we all know as body odour. These glands respond to the hormone testosterone - which is why sweating and BO are more common after puberty.
Link
More on Pheromones, interesting stuff, although most of it is still
up in the air.