I was stung by a jellyfish once in Mazatlan. There is a whole nother story attached to this, but to keep it short, it hurt like hell for several hours. The Red Cross clinic my (now ex-)husband took me to gave me an OTC pain killer and rubbed the sting with lemon juice. I had already been in physical and emotional agony for an hour and the next several hours were spent in mental anguish, so I really can't tell you if it helped or not. The irony of the whole thing is that I was stung while standing in two inches of water, trying to coax my one year old daughter into the ocean, telling her there was nothing to be afraid of.