Causes

Jellyfish deliver their venom through stinging cells on their tentacles. These stings produce a mild burning and stinging sensation and long, whiplike marks that develop on the skin. In most cases these stings can be treated using first aid. If the reaction is severe, however, call your doctor immediately.

Floating colonies of Portuguese man-of-war are easily spotted, but their transparent tentacles can trail invisibly for up to 60 feet. The pain and burning from these stings can be worse than those of jellyfish stings. They may cause breathlessness, stomach cramps, nausea, and shock.

Symptoms

Symptoms of marine-life stings may include:

• Skin rash
• Muscle cramps
• Severe burning pain
• Nausea or vomiting
• Difficulty in breathing
• Shock due to severe allergic reaction

First Aid

• Do not raise a venomous sting above the level of the person’s heart or give the person aspirin, stimulants, or pain medication unless told to do so by your doctor.
• To slow the rate at which the venom spreads in the person’s body, keep the person still. If necessary, carry the person to safety. Remove any rings or other tight items in case the injured area swells. If pain continues, call your doctor.
• Be careful with tentacle pieces. A tentacle can sting even after it is removed from the body of the jellyfish. Carefully remove any embedded tentacles using tweezers, pliers, or forceps, or wrap cloth around your hands. Never rub tentacles off! This will activate more stinging cells.
• Try to find out what caused the sting, if you can do so quickly and without endangering yourself.
• If the sting is not bleeding severely, clean the wound and rinse with seawater or saltwater. Marine-life stings need to be thoroughly cleaned to remove sand, spines, bristles, shell fragments, or coral. If the sting is bleeding heavily, cover it with a towel and apply direct pressure.
• After washing, apply a thick (heavy enough to stick on) paste of baking soda or a vinegar solution (1/3 cup vinegar to 2/3 cup water). Scrape off the paste after half an hour and reapply the solution. Don’t rub the wound or rinse it with fresh water
  because this may discharge stinging cells. If a dangerous reaction or signs of shock occur, call 911.
• Place ice wrapped in cloth or a cold compress on the sting. Be careful not to touch the area with an unprotected hand.
• Call your doctor if pain continues after using self-care.