The rash caused by a jellyfish sting is often red and swollen, and it may even bleed.
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Jellyfish Stings, First Aid 

Picture of Jellyfish Stings, First Aid: The rash caused by a jellyfish sting is often red and swollen, and it may even bleed. Divider line
The rash caused by a jellyfish sting is often red and swollen, and it may even bleed.
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First Aid Guide
Jellyfish are aquatic invertebrates that can sting people who come into direct contact with them. The stingers, which are typically located on the ends of the jellyfish tentacles, contain poisons that are often toxic to humans.

Although most jellyfish are not especially dangerous to people, some are extremely toxic.

Portuguese man-of-war is not actually a jellyfish but rather a colony of small, predatory animals (hydrozoan). However, due to their similarity with jellyfish, this information applies to Portuguese man-of-war stings as well.

First Aid Guide
The rescuer should take care to avoid injury by wearing gloves and protective clothing or any readily available barrier.

  1. Remove the affected individual from the water.
  2. Wipe stingers or tentacles off with a towel.
  3. Wash the affected area with salt water.
Some self-care measures will help some jellyfish stings but will cause an adverse reaction in other types. For that reason, the following should be avoided without advice from a medial professional.
  • DO NOT wash or soak the affected area with fresh water if the injury occurred in salt water.
  • DO NOT apply vinegar, urine, alcohol, or meat tenderizer/water solution to the affected area.
  • DO NOT rub the affected area.
  • DO NOT raise the affected area above the level of the heart.
  • DO NOT give the person medication.
Who's At Risk
Stings from jellyfish most often occur in salt water, while swimming or wading, when a person accidentally comes into contact with the jellyfish. Stings from some jellyfish may also occur if a person comes into contact with jellyfish that have washed onto the beach or detached tentacles in the water. Certain jellyfish tentacles that have become detached are still capable of causing stings for 2 weeks or more. Jellyfish stings sometimes occur in fresh water as well.
Signs and Symptoms
A jellyfish itself consists of a bell shape with suspended tentacles. They open and close their bell-like body to drift and slowly swim in the water.

The sting of a jellyfish may appear swollen, red, and bleeding. The affected area may burn and feel painful.

Additionally, the person who has been stung by a jellyfish may experience the following:
  • Nausea or vomiting
  • Paralysis
  • Sweating
  • Weakness
  • Difficulty breathing
  • Cramps
  • Diarrhea
  • Pain in unaffected areas, such as the groin or armpit
When to Seek Medical Care
Seek medical care if the person is having difficulty breathing, is bleeding profusely, or other body-wide (generalized) symptoms are occurring, such as the following:
  • Nausea or vomiting
  • Paralysis
  • Sweating
  • Weakness
  • Cramps
  • Diarrhea
  • There is pain in an area not directly affected by the jellyfish sting, such as the groin or armpit
Treatments Your Provider May Prescribe
In the case of some jellyfish stings, such as a sting from the box jellyfish of Australia, an antivenin may be necessary to treat the symptoms of anaphylactic shock.

The treatment may vary depending on the type of jellyfish sting. General treatment measures for most jellyfish stings are as follows:
  1. Immerse the sting area in hot water until pain is relieved.
  2. Remove tentacles (if still present) with forceps.
  3. Remove stingers (nematocysts) with shaving cream and a razor.
  4. Administer pain reliever and treat itching.

References/Trusted Links
References

Handal KA; American Red Cross. Part 2: first aid. In: The American Red Cross First Aid and Safety Handbook. 1st ed. Boston, MA: Little, Brown and Company; 1992:59-62.
Last Updated: 22 Dec 2008