the only person i've known with this sort of hygiene issue was jewish. so i have to assume that's what this neighbor is too.
we had a mutual friend at the time who used to spray febreze on him whenever she saw him. it was not as effective as hoped. eventually he failed out of college and moved back in with his mom, so as far i know, the issue ended then. maybe that will happen to your neighbor.
You've only known one stinky person before?
Where do you live?