Medicine for the Outdoors
Medicine for the Outdoors

Dr. Paul Auerbach is the world's leading outdoor health expert. His blog offers tips on outdoor safety and advice on how to handle wilderness emergencies.

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Hot Water for Jellyfish Stings

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There are multiple therapies recommended for field therapy (first aid) for jellyfish stings. These include topical decontaminants, such as vinegar (acetic acid), rubbing alcohol, papain, citrus juice, ammonia, and others; rapid decontamination combined with removal of nematocysts (by scraping, shaving, or abrasion); application of ice or cold packs; and application of heat. In addition, there is the consideration of therapy for an allergic reaction to jellyfish venom(s).

Application of heat, in the form of hot water "to tolerance" (non-scalding) is a relatively new therapy, in comparison to others that have been recommended for years in one form or another. The major proponents for this therapy are Australians, who have observed and evaluated this therapy clinically, predominately in victims of the Australian species of man-of-war jellyfishes. Their observations have been that this therapy is very helpful, as the victims improve clinically, particularly in showing relief from pain.

I am encouraged by this finding, and hope that it proves to be true over the long haul, and not just until it falls out of favor based upon some new recommendation. So, until further notice, here is general advice about how to manage a jellyfish sting:

The following is recommended for all unidentified jellyfish and other creatures with stinging cells, including the box jellyfish, Portuguese man-of-war (“bluebottle”), Irukandji, fire coral, stinging hydroid, sea nettle, and sea anemone:

1. If the sting is felt to be from the box jellyfish (Chironex fleckeri), immediately flood the wound with vinegar (5% acetic acid). Keep the victim as still as possible. Continually apply the vinegar until the victim can be brought to medical attention. If you are out at sea or on an isolated beach, allow the vinegar to soak the tentacles or stung skin for 10 minutes before you attempt to remove adherent tentacles or further treat the wound. In Australia, surf lifesavers (lifeguards) may carry antivenom, which is given as an intramuscular injection at the first-aid scene. There is recent discussion in the medical literature about whether or not antivenom against box jellyfish as currently administered to humans is beneficial. Until further notice, it is likely to be used by clinicians. Notably, the pressure immobilization technique is no longer recommended as a therapy for jellyfish stings.

2. For all other stings, if a topical decontaminant (vinegar or isopropyl [rubbing] alcohol) is available, pour it liberally over the skin or apply a soaked compress. Some authorities advise against the use of rubbing alcohol on the theoretical grounds that it has not been proven beyond a doubt to help. However, many clinical observations support its use. Since not all jellyfish are identical, it is extremely helpful to know ahead of time what works against the stinging creatures in your specific geographic location. For instance, vinegar may not work as well to treat sea bather’s eruption, which is commonly seen in certain Mexican coastal waters; a better agent (also subject to some differing opinions) may be a solution of papain (such as unseasoned meat tenderizer). For a fire coral sting, citrus (e.g., fresh lime) juice that contains citric, malic, or tartaric acid may be effective, with emphasis on the word "may."

Until the decontaminant is available, you can rinse the skin with seawater. Do not rinse the skin gently with fresh water or apply ice directly to the skin, as these may worsen the envenomation. A brisk freshwater stream (forceful shower) may have sufficient force to physically remove the microscopic stinging cells, but nonforceful application is more likely to cause the stinging cells to discharge, increasing the envenomation. A nonmoist ice or cold pack may be useful to diminish pain, but take care to wipe away any surface moisture (condensation) prior to its application.

As I mentioned above, observations from Australia suggest that hot (nonscalding) water application or immersion may diminish the sting of the Portuguese man-of-war from that part of the world. The generalization of this observation to treatment of other jellyfishes, particularly in North America, should not automatically be assumed, because of the fact that application of fresh water worsens certain envenomations. However, the concept is intriguing, and I intend to try it the next time I am stung if hot water is available. (How hot is hot? The upper limit of temperature should be 113 degrees Fahrenheit or 45 degrees Centigrade.) Otherwise, I will continue to use vinegar (e.g., StingMate) or another of the useful topicals.

3. Apply soaks of vinegar or rubbing alcohol for 30 minutes or until pain is relieved. Baking soda powder or paste is recommended to detoxify the sting of certain sea nettles, such as the Chesapeake Bay sea nettle. If these decontaminants are not available, apply soaks of dilute (quarter-strength) household ammonia. A paste made from unseasoned meat tenderizer (do not exceed 15 minutes of application time, particularly not upon the sensitive skin of small children) or papaya fruit may be helpful. These contain papain, which may also be quite useful to alleviate the sting from the thimble jellyfish that cause sea bather’s eruption. Do not apply any organic solvent, such as kerosene, turpentine, or gasoline. While likely not harmful, urinating on a jellyfish, or any other marine, sting has never been proven to be effective.

4. After decontamination, apply a lather of shaving cream or soap and shave the affected area with a razor. In a pinch, you can use a paste of sand or mud in seawater and a clamshell.

5. Reapply the vinegar or rubbing alcohol soak for 15 minutes.

6. Apply a thin coating of hydrocortisone lotion (0.5 to 1%) twice a day. Anesthetic ointment (such as lidocaine hydrochloride 2.5% or a benzocaine-containing spray) may provide short-term pain relief.

7. If the victim has a large area involved (an entire arm or leg, face, or genitals), is very young or very old, or shows signs of generalized illness (nausea, vomiting, weakness, shortness of breath, chest pain, and the like), seek help from a doctor. If a child has placed tentacle fragments in his mouth, have him swish and spit whatever potable liquid is available. If there is already swelling in the mouth (muffled voice, difficulty swallowing, enlarged tongue and lips), do not give anything by mouth, protect the airway, and rapidly transport the victim to a hospital.

To prevent jellyfish stings, an ocean bather or diver should wear, at a minimum, a synthetic nylon-rubber (Lycra [DuPont]) dive skin. Safe Sea® Sunblock with Jellyfish Sting Protective Lotion, which is both a sunscreen and jellyfish sting inhibitor, has been shown to be effective in preventing stings from many jellyfish species.

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Dr. Paul S. Auerbach is the world’s leading authority on wilderness medicine.

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