The fact that the broken sensory nerve of the traumatized hand has no sensation and becomes numb after being scalded by boiling water may be due to the fact that part of the sensory nerve is undamaged or the gradual recovery after anastomosis of the traumatized nerve of the hand, etc., which are explained as follows. 1. Part of the sensory nerve is not damaged: the broken sensory nerve of the hand trauma will lead to no sensation in the area it innervates, while the sensory function of the area innervated by the undamaged nerve is normal, which will be paralyzed when being scalded by boiling water. 2. Recovery after nerve anastomosis: After hand trauma, if the nerve dissection anastomosis is performed in time, the sensation and function of the hand part can be recovered slowly, if burned by boiling water, although the pain sensation is not sensitive, but there will be a phenomenon of numbness. Nerve damage recovery is slow and difficult to return to normal, patients should pay attention to protect the affected limb, avoid pressure and burns, if you feel uncomfortable, please consult a doctor in time, so as to avoid delaying the condition.