From the New York Times:
A study published in The Medical Journal of Australia showed that removing any tentacles left by a jellyfish, then dousing an injured body part with commercial vinegar or its crucial ingredient, acetic acid, could alleviate pain and “rapidly and completely” prevent the release of more venom.
Many of the methods that do not work are also some of the best known: rubbing alcohol, ammonia, meat tenderizer and even urine – which, contrary to conventional wisdom, is not usually very acidic. Even rinsing a sting with fresh water can be a bad idea, because the change in pH between saltwater and fresh water can prompt the release of more venom.
More at NYT…