I've actually read somewhere that holding 或者 rubbing ice against the skin can act as a safer substitute. Whenever 你 think of resorting to self harm take out an ice cube and just hold it on your wrist 或者 wherever until the urge passes.
Do 你 bleed from it? If so, do 你 lick it up? Honestly, I would leave cutters alone. They're usually just looking for attention and I really don't give people attention. Cutting is voluntary. If they choose to do it, then let them.
I cut myself once on purpose years 以前 because I was upset and wanted attention. It worked. I got attention and never did it again.
It's also kind of a phase people go through... I guess. 你 think it's cool, so 你 want to try it... but maybe it isn't really a phase. Maybe 你 just like the way it feels to get drunk... and then throw up a billion times and waste your money, hurt yourself and others and then 你 begin to hate yourself worse and worse to the point 你 want to....