Stings are most common during summer months because that’s when the beaches are the most active. Fortunately, most stings from jellyfish in US waters only cause pain, with little risk for allergic reactions or death. Symptoms of envenomation in humans vary with the species but can range from a mild sting to agonizing pain and systemic symptoms. Anaphylaxis can occur.
The first thing to do when dealing with a jellyfish sting is to assess for loss of responsiveness, signs of shock or anaphylaxis and call 9-1-1 if present. Begin CPR as indicated.
If there is no sign of an allergic reaction, remove any remaining tentacles by lifting or pulling while avoiding manual contact. Rinsing the affected area with sea water can also be done.
Following removal of remaining tentacles, use hot water immersion/irrigation for 20 minutes or until pain is relieved. The temperature of the water should be around 106-113°F or as hot as tolerable that is not scalding. If a tub for hot water immersion or a shower is not available, a chemical heat pack can be applied over the affected area.
Vinegar (acetic acid) was confirmed to result in worsening stinging from some species of jellyfish, and is therefore no longer recommended in the majority of jellyfish stings in US coastal waters.
If topical lidocaine gel is available it can be applied to any stinging cells that may be remaining on the skin to start to relieve pain.