Everyone's different but I have yet to experience any side effects. You can look each supplement up on google if you want to know more.
As I stated above some people have problems with biotin breaking them out but apparently if you take with other b-group vitamins you're ok.
I'm guessing if you stop taking them, your hair growth will slowly go back to normal once the mineral/vitamin has been depleted from your system. I find when I take MSM continually I get goo growth, where as I get slower growth if I'm not so consistent.