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Portuguese Man-of-War Sting

The Portuguese man-of-war (also called “bluebottle”) is a jellyfish-like marine animal found in tropical oceans and bays. Man-of-war tentacles have coiled stingers that have a very powerful and painful venom. The tentacles can grow to 165 feet long. The man-of-war sting is meant to paralyze small fish until it can be eaten. In humans, reactions can be mild to moderate. In rare cases, it can be life threatening.

After a sting, the tentacles leave long, stringy red welts on the skin. The welts last from minutes to hours. There is local pain, burning, swelling, and redness. This rash may come and go for up to 6 weeks. Cramps, fever, sweating, weakness, faintness, dizziness, nausea, vomiting and diarrhea may also occur in stronger reactions. Over-the-counter medicines are used to treat generalized symptoms of pain, itching, and swelling. Severe reactions require hospital treatment.

Prevention and care

These tips can help you prevent and care for a sting:

  • Before swimming in oceans or bays, check local beach reports for warnings of Portuguese man-of-wars. Don't swim in the water when they are present.

  • If you find one washed up on the beach, do not touch it. Even dead man-of-wars or detached tentacles can sting.

  • If you are stung, first remove tentacles with a gloved hand, stick, towel, or swim fins. Rinse the area with salt water.

  • Put the affected area in hot salt water for about 20 minutes. If there is no hot water, put rubbing alcohol on the area to inactivate the stinging cells. Leave in place for 30 minutes.

  • Get medical attention for moderate to severe reactions.

Home care

The following guidelines will help you care for yourself at home:

  • If your doctor has given you medicines, take them as directed.

  • Put an ice pack over the injured area for 20 minutes every 2 hours for the first day. Do this 3 to 4 times a day for the next few days until the pain and swelling improve.

  • Over-the-counter creams with hydrocortisone and benzocaine may reduce the itching and local pain.

  • Oral antihistamines containing diphenhydramine can be found at drug stores and groceries. Unless a prescription antihistamine was given, you may use these to reduce itching if large areas of the skin are involved. Use lower doses during the daytime and higher doses at bedtime since the drug may make you sleepy. [NOTE: Do not use antihistamines with diphenhydramine if you have glaucoma or if you are a man with trouble urinating due to an enlarged prostate.] Antihistamines with loratidine cause less drowsiness and may be better for daytime use.

  • You may use ibuprofen for inflammation and pain, unless another pain medicine was prescribed. [NOTE: If you have chronic liver or kidney disease or ever had a stomach ulcer or GI bleeding, talk with your doctor before using these medicines.]

Follow-up care

Follow up with your doctor or as advised by our staff or if you develop a recurring rash.

When to seek medical care

Get prompt medical attention if any of the following occur:

  • Symptoms worsen

  • The rash becomes more red, painful, warm, or drains fluid, or if open sores appear

  • Shortness of breath or chest pain

  • Dizziness, weakness, or fainting

  • Fever of 100.4°F (38ºC) or higher, or as directed by your health care provider

  • Pink or red urine


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