I've often wondered what it is that's so enjoyable sniffing the gusset of a worn pair of panties. I can understand if a women has dressed up for sex and her panties are soaking with her juices, I get that but not all day undies.
Pheromones: are chemicals capable of acting like hormones outside the body of the secreting individual, to impact the behavior of the receiving individuals.
There are alarm pheromones, food trail pheromones, sex pheromones, and many others that affect behavior or physiology.