I didn't know about the hair dyes, but after getting a "black henna" tattoo on a beach vacation I came home and looked it up (because I knew henna was a natural product and red, and wondered how they made it black)... and was pretty shocked to see that I'd had some acronym'd chemical painted on my skin without a word about what it was, much less the possible effects or what to do in case of reaction! I had it done at a restaurant -- this was being presented as a "pass the half hour wait" entertainment thing!

Fortunately I had no problems with it, but, yeah -- quite a shocker!

I have never tried natural hair dyes (my hair's too dark for lighter coloured dyes unless I bleach it first), so I didn't know how they got various colours -- in fact, didn't know there even were "henna" hair dyes marketed in different colours! :D But I'm amused at the cassia -- that's what most Americans think of as cinnamon. (Or else it's something closely related; I know the genus but not the epithet for the spice.) What a useful plant! :D