Since 1997
Portuguese Man-of-War
by DAN Medical Team on March 4th, 2016

​While honeymooning in the Caribbean, my wife and I were snorkeling about 50 feet/15 meters offshore. Suddenly, my wife screamed and began wrenching her body, trying to pull something off of her, even though I couldn't see anything. We made it back to shore, but she began vomiting uncontrollably within seconds. She felt spasms in her back and had trouble breathing and standing. She had deep red lash marks on her forearm area, extending around to her elbow and neck.

Since returning home, we have been trying to determine several things: What stung her? Is she allergic, or was it merely a severe sting in a sensitive area? What can she do to prevent a fatal recurrence? Is there a way to test if she is allergic? We have also been told that the next time she is stung could be worse because she is sensitised - is this true?
​Your experience is consistent with the sting of a Portuguese man-of-war (Physalia physalis). There are other members of the coelenterate phylum which can produce a similar reaction, but Physalia is the most common offender. The animal has a "sail" which floats on the surface and moves the animal in the direction of the wind. There are one or more long tentacles extending 33 feet/10 meters or more, and they are responsible for most stings.

In rough weather, the tentacles may become separated from the sail and drift just below the surface, where they are practically invisible. The toxin is potent enough to have produced the entire problem your wife experienced without an allergic component. However, the toxin is a potent antigen and probably produced an immune response so that she now may be allergic to the venom as well as susceptible to the toxic effects. Another exposure may consequently be more severe. Fatalities, however, are rare and usually appear to result from drowning because the pain and the sting's toxic effects sometimes weaken swimming abilities.

​Prevention of injury is best accomplished by avoiding contact with the animal. They are frequently found together in large numbers. When many "sails" are visible, swimming or snorkeling is not a good idea. Since the man-of-war remains near the water surface, diving might be possible - provided it's done with great care during entry and exit. Protective apparel such as full wetsuit or thick dive skin prevents contact of the toxin-containing nematocysts. Keep in mind that nematocysts can remain potent for hours and be transferred from dive apparel and gear to bare skin when handled. If the wind is blowing onshore (from the ocean toward land) the animals are more likely to be present than with an offshore wind. In the event of a repeat sting, the EpiPen (which contains epinephrine) might modify the allergic component of the reaction, but it would not relieve the toxic effects.

Posted in Dive Safety FAQ    Tagged with no tags


St.Elmo - June 18th, 2016 at 2:42 AM
Ok , but what is recommended treatment if stung ?
Gerry Potgieter - June 21st, 2016 at 12:29 PM
When I was a Kid swimming off the beaches of Durban South Africa there where frequent stings by what we knew as Blue Bottles , my mother all ways had some vinegar with her which provided some relieve and warm thermo flask water. Not a medical solution to people with allergies but brothers,sisters and other kids survived to swim again.
Dr Frans J. Cronje - June 23rd, 2016 at 4:04 AM
Thanks for the comments and questions.

The main principles with all Hazardous Marine Life Injuries are:

(1) ABC's - life support as needed;
(2) Removing or neutralizing the primary injury, toxicity or allergy, and then;
(3) Preventing or mitigating any secondary complications.

So, for the Portuguese Man-of-War stings, the initial emphasis is:

(1) To ensure that the person does not drown (due to pain, paralysis or anaphylactic shock); then

(2) Any remaining tentacles can be neutralised and rinsed off with (ideally) vinegar or - if this is not available - clean sea water - to avoid additional stinging cell discharges. Vinegar is also effective - due to the superficial nature of this type of envenomation - in neutralizing the venom through its acidity. For deeper forms of envenomation:

(3) hot compresses or immersion in hot water (45 degrees centigrade) for 15 minutes at a time and thereafter as pain returns for a total of 90 minutes. Hot water is usually unnecessary for Portuguese Man-o-War stings. However, it is the only practical alternative to break down the venom in the case of deeper stings - such as with lion fish, stone fish or stingrays. Then, after the initial treatment, local anaesthetic cream (e.g., EMLA) or cortisone containing creams may be applied to reduce the inflammation and pain that follows the initial envenomation. Medical attention is recommended for any effects involving cardio-respiratory or nervous system function (e.g., fainting or altered consciousness), or any open wounds or blistering of the skin.

All marine life injuries carry the potential risk for tetanus. So it is important to consider whether an affected individual is immunized against tetanus.

Thanks for the questions!
Leave a Comment