The stinging cells on a jellyfish tentacle are called nematocysts. It's easy to see in this picture where the nematocysts were along the tentacle. The raised bumps clearly mark the reactions to the jellyfish toxin.
The first step in treating jellyfish stings is to remove any parts of the tentacle still touching the skin -- just not with bare hands. Jellyfish stinging is automatic, which means the tentacle no longer has to be attached to the body of the jellyfish to keep stinging. You have to spray, rinse or brush off the tentacles first. Use whatever is available.
For more jellyfish treatment steps: How to Treat Jellyfish Stings.
Have a jellyfish sting? Take a picture and submit it here.
Any opinions expressed here are for educational purposes only and are not intended for diagnosis.