Your child gets stung by a jellyfish.
Wrong response: Put rubbing alcohol or urine on the wound.
Smart move: Rinse it with sea water (fresh water will make the wound even more painful) and remove any visible tentacles, recommends Paul Auerbach, MD, an emergency physician at Stanford University Medical Center and author of Medicine for the Outdoors. Then soak a napkin or cloth with white vinegar and apply continuously until your child no longer seems to be in pain. (Lifeguards often carry a vinegar solution. But if none is on hand, send someone to get some from a nearby home, store, or restaurant.) Vinegar will deactivate the stinging cells of most jellyfish, which otherwise can cause pain for 30 minutes or more. If your child has any sign of an allergic reaction (difficulty breathing, wheezing, or hives), seek emergency medical care right away.