Without color; lacking characteristics which give variety. blank (Adjective). Free from writing, printing, or marks; having an empty space to be filled in; as, blank paper; a blank check; a blank ballot. blank (Adjective). Without expression.
Yes they do damage hair. Every time I have tried one ,I wound up looking like a Q-tip or my head looked like cotton. A perm will damage even more and look worse if you have been coloring your hair. There's chance of it looking okay if you don't color your hair.
You can perm your hair after surgery. Perming/dying has nothing to do with the digestive system. ETA: I see your reply above about the falling out of the hair. Yes, I guess that would be an issue. But in the long term yes you can perm/dye.