Not that common, happens to a few but rarely. Most of the time the hair would probably get worse anyway and the finasteride just doesnt make a difference when ppl complain.
If youre contemplating not getting on it think to yourself, if in 6 months or a yeAr your hair is way worse are you going to get on it then? Because if so you may aswell get on it as early as possible. If you think you can live without it then do so
