"Is skin-cutting ("cutting," "self-harm") actually unusually dangerous?" @ Quora

No judgements, but if you self harm please be aware of how deep you are cutting..
Answered by Sophie Dickins, 
Credit @ Quora "It can be. Superficial wounds aren't particularly dangerous in and of themselves, especially if they are done with a disinfected razor, but there is still potential for infection as with any open wound. Plus, the cutter is likely to be hesitant to show their cuts to someone if they do become infected.

Cutting (as far as I'm aware) is more often used as a coping mechanism for anxiety/depression/stress/etc than as an enjoyable passtime. Therefore it indicates that the cutter is experiencing psychological distress, which is definitely greater cause for alarm than, say, tennis practice. Plus, unlike sports, the cuts are the purpose, rather than just an occaisional undesirable side effect.

Another cause for concern is the fact that superfical cuts can lead to deeper ones. Like anything that causes a release of endorphins or "high", you need more and more to get the desired effect as you become acclimated.

Lastly, those who cut sometimes enter what could be described as an "altered state". Some cutters report they don't feel pain while cutting, only emotional release. The pain comes later. This lack of awarenes of pain could lead to very deep cuts, which would require emergency medical attention."