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. Jellyfish tentacles often detach from the jellyfish and can easily remain stuck to skin and clothing, where the nematocysts can continue to sting. 

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 by calling 911.

To treat a localized sting:

  1. Inactivate the tentacle discharge with a topical application of 5% acetic acid (full-strength vinegar—do not use water!)
  2. Remove tentacles by plucking with tweezers (do not scrape or rub, which can cause additional release of venom)
  3. Immerse the affected area in hot water up to 113°F (45°C) for 30-90 minutes
  4. Pat the skin dry
  5. Apply a 4% lidocaine spray to the skin (available over the counter at drug stores)

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.

What NOT to do if you've been stung

There are a number of "home remedies" that medical research shows to be ineffective:

  1. Do not rinse with fresh water or shave the skin, as this can cause additional tentacles to discharge 
  2. Do not apply alcohol, baking soda, meat tenderizer, shaving cream, or urine as these are not helpful and some may exacerbate the pain.