I think they are sex hormones or some sort of transmitters that humans emit which creates sexual chemistry between a man and a woman...in order to procreate...but I'll have to double check that when I do my research on it and get back to you. :)
Wow...I've never heard about them causing a calming effect. That's so interesting. I still need to carve out some time to do a bunch of research on them and share the info with all of you.