American Oceans

Can a Portuguese Man o’ War Kill You?

The Portuguese Man o’ War is not often deadly to humans, but it can certainly do some damage!

portuguese man o' war capable to kill human

This not-quite jellyfish may be very pretty to look at, but it is certainly not a creature you want to shake hands – or tentacles! – with.

How Dangerous is a Portuguese Man o’ War?

A Portuguese Man o’ War is not famous for killing humans, but it is famous for harming them!

portuguese man o' war dangerous sting

Traveling in groups of up to 1000, you do not want to get stuck swimming with them. There are two ways that a Portuguese Man o’ War is dangerous other than its’ actual sting. 

First, the dangerous creature looks like a blue plastic bag, and likes to swim relatively close to the surface. What you may think is trash is certainly not your treasure!

Second, the tentacles of the Man o’ War can stretch to unimaginable lengths: up to 100 feet. Just because you can’t see the jellyfish-like creature doesn’t mean it can’t reach you.

What Happens If A Portuguese Man o’ War Stings You?

A Portuguese Man o’ War sting is rarely dangerous, but it is certainly not a fun experience.

portuguese man o' war stings warning on beach

The tentacles of this oceanic creature have a purpose of delivering venom in order to kill or paralyze fish. In humans, it can cause angry welts to appear on the skin.

The stings are not just painful. They have, in some instances, caused intense allergic reactions and even heart failure in some people (though rare). 

What To Do If a Portuguese Man o’ War Stings you?

If a Portuguese Man o’ War stings you, leave the water and find help. If the tentacles are still on you, do not take them off with your bare hands.

portuguese man o' war tentacles do stings

Instead, wash them off with salt water (not fresh water as it could cause the sting to become more intense).

Icing the stung area is also recommended to decrease swelling and help with the pain.

If you feel lightheaded, dizzy, or are having trouble breathing, seek immediate medical attention. 

portuguese man o' war on salt water seaside

How to Avoid getting Stung by a Portuguese Man o’ War?

First, always listen to the lifeguards! They will often ask people to get out of the water if they suspect a Portuguese Man o’ War (or anything else potentially dangerous!) in the water.

If you are going to a beach without a lifeguard, look to see if there are any signs warning of Portuguese Man o’ War in that area.

If you see a Portuguese Man o’ War when you are swimming (again, it looks like a blue plastic bag but beneath the surface of the water) leave the water immediately.

Tell a lifeguard what you saw and they will determine if it is safe or not. If you see the creature on the beach, do not touch it, even if it is dead.

Portuguese Man o’ War can sting even days after its death, so while it may be tempting to touch, it won’t have a great outcome for you.

Research the location you are planning to go swimming at. Portuguese Man o’ War are a common site in tropical and subtropical waters.

If your beach vacation is in a warm part of the world, it may be best to do some research and be on the lookout!


The Portuguese Man o’ War is a pretty creature with a big sting. While it is best to avoid this jellyfish-like being, it is always a good idea to know what to do if you are ever stung by one.


  • I came across a massive one in a beach in west wales. I’m so glad I didn’t touch it. It was the size of a rubber tyre. Purple and blue with incredibly long tentacles. This was before smart phones so I don’t have a picture.

  • My dear friend G. Jeanette Thorbecke MD PhD (1929-2001) while swimming in Hawaii got stung by a CNIDARIA and died from the toxin (anaphylactic shock).

  • I got stung by one yesterday at Panama City Beach Florida. I was just past the pier next to the Alvin’s that is 3 minutes from Bikini Bottom Resort. I thought it was a jelly fish until researching the nausea.

  • I got stung by one while at Surfside (south part of Galveston Island along the Texas coast of Gulf of Mexico). It hurt soo bad! Not initially, but as soon as I left the water I was pretty much in tears. That was 3 days ago. I’m home now but suffering from nausea and sever migraines. I’ve been stung by jelly fish many times in the past, this is a new level. It’s starting to burn again, and I’m worried that it’s why I’m having nausea and migraines. I’m highly allergic to bees and wasps. Do I need to see my doctor or go to the ER?