Re: Why does it sting when you put salt on a wound or cut?

Whenever a person gets a cut, pain receptors (called nociceptors) around
the area of the wound detect that the skin has been damaged. These pain
receptors send electrical signals to the spinal cord, where
neurotransmitters (chemical messengers) cause other neurons to convey the
signal to the brain. The brain detects these messages as pain.

Nociceptors can also respond to other changes in the physical environment,
including ion concentration. Salt, which breaks up into sodium and chloride
ions, increases the concentration of ions in the wound area. As a result,
more nociceptors are activated, and more pain is perceived. 

Adding water to a salted wound dilutes the concentration of these ions, so
fewer pain impulses are sent.