What is jellyfish stings?

Problems from jellyfish or Portuguese man-of-war stings may develop right away or be delayed for several hours or days. A severe allergic reaction (anaphylaxis) may affect any body system and require emergency care. Symptoms can include:

• Shock.
• Severe pain.
• Swelling of the lips, tongue, mouth, throat, neck, ears, eyelids, palms, or soles of the feet (angioedema). Swelling is most serious when it involves the airway and interferes with breathing.
• Coughing, wheezing, difficulty breathing, or a feeling of fullness in the mouth, throat, or neck.
• Lightheadedness, confusion, or agitation.
• Headache, dizziness, or vertigo.
• Nausea, vomiting, diarrhea, and stomach cramps.
• Fever and chills.
• Hives and flushing of the skin. These symptoms often occur with other symptoms of a severe reaction.
• Muscle spasm, muscle cramps, joint pain, or generalized aching.

The reaction that you have to a jellyfish or Portuguese man-of-war sting depends on many things. The potency of the venom changes with the type of jellyfish and also is stronger during some seasons than in others. Other things that affect the severity of your reaction include:

• Your size, age, and general health.
• The location and how much of your body (surface area) was stung.
• The size or number of jellyfish or tentacles that stung you.

The pain from jellyfish and Portuguese man-of-war stings may be intense and may last for several hours. The skin at the site of the stings may look dusky or bluish purple. Blisters and deep sores (ulcers) may develop. Healing is generally a slow process that may take many weeks. Permanent scars may occur at the site of a sting.

Small children are at risk for stings in the mouth if they put a jellyfish or portion of a tentacle in their mouths. A sting to the mouth or throat can cause sudden and severe swelling, which can be life-threatening.

The rash and skin irritation that occurs with minor jellyfish or Portuguese man-of-war stings will usually go away with home treatment. Seabather's eruption is a rash that develops from the stings of jellyfish or sea anemone larvae. Although these rashes are annoying, they are not a serious medical problem.

When an itchy rash occurs several days to weeks after a sting, the rash may mean a delayed skin reaction has occurred. A delayed reaction can occur many times over the course of 1 to 2 months following a sting. You may have a fever, weakness, or joint stiffness or swelling. Medical treatment may ease the discomfort and prevent complications from a delayed reaction.

Jellyfish or Portuguese man-of-war stings may cause blisters or small, shallow sores (ulcers). The skin at the site of the stings may look dusky or bluish purple. Healing may take many weeks. Permanent scars may occur at the site of a sting.

Sores usually heal without medical treatment. Wounds should be cleaned 3 times each day and covered with a thin layer of antiseptic ointment. But when a deep sore develops, you may need medical treatment to help the sore heal and prevent infection.