system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 How come water based liquids sting wounds but oil based liquids or ointments don’t?
gpt
Our bodies use water, in our blood, as the main fluid to move stuff around. So water is special to us in a way that oils are not, when water touches our wounds, it's sort of like the right plug fitting into the right outlet. 

Our nerves, which are exposed in a wound, use chemicals called "ions" to transmit signals up to our brain. When water touches an exposed nerve, if that water contains too many ions (like salty water) or too few ions (like distilled water) it can cause the nerves to misfire and transmit a signal to the brain that we perceive as "stinging". If the water has just the right ion balance, which we call "saline water", it wouldn't trigger that sensation.