The best treatment for you may depend on the type of jellyfish that stung you. But most stings can be treated with these simple remedies:
- Remove stingers. Remove any pieces of jellyfish tentacle in your skin by rinsing the wound with seawater. You can also try gently scraping off the stingers with the edge of an ID card or a credit card. Avoid getting sand on the wound. And don't rinse with fresh water or rub the area with a towel, as these actions may activate more stingers.
- Rinse with vinegar or apply a baking soda paste. Rinse the affected area with vinegar for about 30 seconds. Or apply a paste of baking soda and seawater. Each method may deactivate the stingers of some types of jellyfish.
- Take a hot shower or apply ice packs. Hot water — as hot as you can tolerate but not above 113 F (45 C) — and ice packs may help ease pain.
- Take a pain reliever and apply lotions. Apply calamine lotion or lidocaine to help relieve itching and discomfort.
Remedies to avoid
These remedies are unhelpful or unproved:
- Human urine
- Meat tenderizer
- Solvents, such as formalin, ethanol and gasoline
- Pressure bandages
source: http://www.mayoclinic.org/diseases-conditions/jellyfish-stings/basics/lifestyle-home-remedies/con-20034045