There's a lot of truth there about the hair and odor. It's like a mop or sponge up there just sitting absorbing odors from where ever you are at.
Back when I'd have a smoke(with my buds having some buds, LOL!), I noticed when I washed my hair, how much of the smoke was captured by my hair. I could easily see it in the drain water. I could also run my hand through my hair and smell the smoke on my fingers. I'm not a smoker, so those type smells are very noticeable to me.
Just use those scent-free soaps free of perfumes, etc, by taking a bath/shower before each hunt and that'll be better than wearing a shower cap.
Another issue is we lose the most heat out the top of our head. It is also more evident when it's cold out and if your head is warm enough, you can literally see the steam rise from it. Therefore that's a moisture build up(sweat) which can lead to an odor source as well.
So david33, whoever told you that about the hair, is not that far off.
Night Crawler... Here's a tip for yah:
A lil' Irish Spring never hurt anyone. LOL!