The pain and harm from a jellyfish sting can run from none-at-all to very soon deadly. Barbed stingers on the long tentacles trailing after the jellyfish's namesake dome are full of venom that can penetrate the skin and release toxins into the surrounding skin. This venom can even enter the bloodstream and result in systemic ailments including vomiting, muscle spasms, fever, joint inflammation, and breathing difficulties. In particular, the venom of the box jellyfish is extremely potent and you should pursue professional care immediately.
Jellyfish can be found in all of the world's oceans, along beaches, and even sometimes in freshwater. Fortunately, most jellyfish stings are relatively minor. In fact, the pain and inflammation of a jellyfish sting can be addressed fairly quickly with simple home remedies. In fact, many beaches with jellyfish populations will store bottles of vinegar near the beach - a common natural anti-venom to counteract the toxin injected into a victim's wounds. Still, prolonged or advancing pain and other sting symptoms require a doctor's care.
Splash with vinegar, then use hot water (hotter than bathwater) to rinse off the tentacles or salt water, if hot water is unavailable. Do not touch the tentacles directly! Continue to brush off the tentacles using gloves. Try soaking in hot water and possibly ice packs to relieve pain and itching, as well as an analgesic.
