I stopped using shampoo last summer and I haven't looked back. I scrub my scalp with a small bit of baking soda weekdays and then rinse my long hair with apple cider vinegar a few times a week. My hair is soft and never greasy. A couple times I got a whiff of "head", so I added a cinnamon stick to the vinegar rinse I use for my hair. The cinnamon was so strong after a couple days I had to water it down.
What I found though, was my armpits (I don't use deoderant either) faintly smell of cinnamon! It can't be my nose playing tricks on me, because I only smelled it after wiping my pit with my hand. There's really no other way I could have cinnamon in my system other than this hair rinse.
My question: could I overdose on cinnamon? The smell is not overpowering, and is actually kind of neat to have cinnamon flavored pits, but wow, I never thought something I put on my hair for literally seconds could absorb into my skin enough to smell coming out my pores!
Oh, the weirdest part is that only my RIGHT pit smells like cinnamon! It also seems to be the more active pit normally.