Why Do Jellyfish Sting?

Jellyfish sting because they have tiny little stingers called nematocysts on their tentacles. When a person touches them, the stingers pop open and poke the skin, releasing little toxins that cause pain and sometimes an itch or redness.

Think of it like tiny needles hidden in your hair, when you brush against something with those needles, they shoot out and make you feel a sting. That's how jellyfish protect themselves from bigger animals (and swimmers)!