system
Given the following post, respond as if you're commenting on Reddit:
human
What causes a burning sensation when you get salt in an open wound?
gpt
It is just basic electrophysiology. When you have an open wound, the solution around nerve fibers is directly accessible. Nerve fibers work via gradients of sodium and potassium inside vs outside the cell. If you really boost the sodium concentration outside the cell, it becomes hyperexcitable. Now, it is a wound, so C fibers (nociceptors) are going to be active anyway. The salt is going to act like an amplifier. 
  
It is different from the case of lemon juice, which alters the local pH. The C fibers are directly sensing the pH and sending a signal that your brain interprets as pain.