Jellyfish Stings

Why and how do jellyfish sting?

Because jellyfish are slow-moving, weak animals, they use stinging tentacles to capture and immobilize their prey. These tentacles are covered with stinging cells called nematocysts that each discharge a tiny, harpoon-like structure that carries venom. These nematocysts can continue to fire even after the tentacle has been detached from the jellyfish.

How do I avoid jellyfish and their sting?

The sea nettle Chrysaora chesapeakei is the species of jellyfish in Chesapeake Bay most responsible for painful stings. Knowledge of the sea nettle's ecology and distribution will help swimmers and anglers avoid this animal and its stinging tentacles.

  • Avoid areas where flotsam might collect. Because sea nettles and other jellyfish are planktonic animals that move with the tides and currents, they often aggregate along windward shorelines or where a flood tide encounters an obstacle.
  • Wear protective clothing. Covering skin with tight clothing and covering exposed areas (such as lips and face) with petroleum jelly will prevent many stings.
  • Swim early or late in the season. Sea nettles are only present in the Bay during the summer (~ May to September) when water temperatures are between 78 to 86o F.
  • Swim in freshwater or the ocean. The sea nettle is limited to a relatively narrow range of salinity (brackish waters of 10 to 16 parts per thousand).
What do I do if I've been stung?

While uncommon, a jellyfish sting can cause an allergic reaction, causing swelling throughout the body and potentially restricting the airway. If this happens, use injectable epinephrine (adrenaline) or an oral antihistamine, and quickly seek medical attention.

To treat a localized sting:

  1. Remove the tentacles: Jellyfish tentacles often detach from the jellyfish and can easily remain stuck to skin and clothing. To remove the tentacles, rinse the stung area gently with salt water, and carefully remove any tentacles with tweezers. Do not rinse vigorously or with fresh water, as this can cause additional tentacles to discharge.
  2. Apply a slurry of baking soda. Even after removing visible tentacles, small pieces and undischarged nematocysts can remain on the skin, and they need to be deactivated to prevent further stinging. The best method for deactivating sea nettle nematocysts is to apply a paste of baking soda and water. DO NOT apply vinegar, alcohol, meat tenderizer, or urine as these have been shown to activate sea nettle nematocysts and cause further envenomation.
  3. Treat the sting: After removing any potential for further stinging, clean and dry the affected area. A topical application of ethanol-Benzocaine blends or a high concentration of lidocaine can help with pain relief. Again, applications of deionized water, meat tenderizer, ethanol, urine, or vinegar are not helpful and can exacerbate the pain.

Please note: The aforementioned treatment suggestions are for the sea nettle Chrysaora chesapeakei. Because jellyfish venoms can differ by species, age, geographic location, and body part (tentacles vs. body), these same  treatment suggestions may not be the most effective in all situations.

  • Seymour, J.E. Are we using the correct first aid for jellyfish? The Medical Journal of Australia 2017, 206 (6): 249-250.
  • Cegelon L, Heymann WC, Lange JH, Mastrangelo G. Jellyfish Stings and Their Management: A Review. Marine Drugs 2013, 11: 523-550.
  • Burnett JW. Treatment of Atlantic cnidarian envenomations. Toxicon 2009, 54:1201-1205.