I've used scents in the water, and to be honestI wasnt particularly impressed with them. Not for any harmful reaction to skin or anything, but I just didn't think that the smell lasted very long, or was very strong. I just used the pour in stuff from the bottles, (being very technical here!!) While we could smell it when it was poured in, and for a (very) short time afterwards, the scent soon dissappated.
Having said that, the hot tub is, afterall, outside, so a light breeze could soon take the scent away.....plus, you dont smell something as strongly after you get used to it.
I also found that after using this, I was left with a scum line round where the water line was. Agagin, I'm not sure if this was def caused by the scent, but the only time it happens is when we use it.
Hope this is helpful
saz