Contact with a jellyfish tentacle can trigger millions of nematocysts to pierce the skin and inject venom. Only some species' venom cause an adverse reaction in humans. When a nematocyst is triggered by contact by predator or prey, pressure builds up rapidly inside it up to 2,000 pounds per square inch until it bursts!! A lance inside the nematocyst pierces the victim's skin, and poison flows through into the victim. Touching a jellyfish can be very uncomfortable, occasionally requiring medical assistance; sting effects range from no effect to death. Even beached and dying jellyfish can still sting.
Treatment and How to Avoid This:
The three goals of first aid for uncomplicated stings are to prevent injury to rescuers, deactivate the nematocyst, and remove tentacles attached to the patient. Rescuers usually wear barrier clothing. Deactivating the nematocysts prevents further injection of venom. Vinegar can help. You could also scrape the infected skin. To prevent getting stung: Avoid jellyfish areas, Wear a wetsuit, if there is no escape, stay calm, and if you get stung, get treated immediately