Portuguese Man-of-War Sting

The Portuguese man-of-war (also called a 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 they 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, don' touch it. Even dead man-of-wars or detached tentacles can sting.

  • If you are stung, rinse the area with saltwater. Apply concentrated vinegar solution if available. This will inactivate the stingers and prevent the release of more toxin. Then with a gloved hand try to remove the tentacles.

  • Put the affected area in hot saltwater for about 20 minutes.

  • Get medical care for moderate to severe reactions.

Home care

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

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

  • Well after the sting was treated and all tentacles were removed, put an ice pack over the injured area for 20 minutes. Do this 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. To make an ice pack, put ice cubes in a plastic bag that seals at the top. Wrap the bag in a clean, thin towel or cloth. Never put ice or an ice pack directly on the skin.

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

  • Oral antihistamines containing diphenhydramine can be found at pharmacies and grocery stores. Unless a prescription antihistamine was given, you may use these to reduce itching if large areas of the skin are affected. Use lower doses during the daytime and higher doses at bedtime since the medicine may make you sleepy. Don't use antihistamines with diphenhydramine if you have glaucoma or if you are a man with trouble urinating due to an enlarged prostate. Some antihistamines cause less drowsiness and are a good choice for daytime use.

  • You may use ibuprofen for pain and swelling, unless another pain medicine was prescribed. Talk with your healthcare provider before using these medicines if you have chronic liver or kidney disease or if you have ever had a stomach ulcer or GI (gastrointestinal) bleeding.

Follow-up care

Follow up with your healthcare provider, or as advised. Also follow up if you have a rash that keeps coming back.

Call 911

Call 911 if any of these occur:

  • Shortness of breath or chest pain

  • Dizziness, weakness, or fainting

When to get medical advice

Call your healthcare provider right away if any of these occur:

  • Symptoms get worse

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

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

  • Pink or red urine

Was this helpful?

Yes No

Tell us more.

Check all that apply.

Last question: How confident are you filling out medical forms by yourself?

Not at all A little Somewhat Quite a bit Extremely

Thank You!

© 2000-2020 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.