Origin/Meaning of "Pour salt on my wound"

Salt on an open wound stings, so pouring salt on someone's wound speaks of making someone's hurt hurt worse. But, was salt ever used as a medicine?

Rubbing salt in the wound may have stung a bit but it did help to control infection. A more effective infection preventative for an open wound is to fill it with honey or sugar and bind it up: all supposing that you are physically isolated and can't get proper medical attention. There is a downside, you need to carry sugar with you or be on good terms with the local bees.