i used to straighen my naturaly frizzy hair along time ago, 1992.
yes by all means you can chemicly straighen naturaly growing hair.
but once you subject the hair to moisture it will retun to its natural state.
the bain of my life or so i thought.
in later years i straighened my hair as i dried it with mouse and a barrel bristtle brush.
worked a treat, it wasent megga straight as it chemicaly would have been but it was a compromise on chemical or product route.