Jellyfish Stings and Prevention

Check out this video about jellyfish stings from TED-Ed

Jellyfish use their stinging tentacles to catch prey, however these stingers can hurt humans and impact activities across the globe. Worldwide, there are an estimated 150 million jellyfish stings annually [1]. Common symptoms of jellyfish stings are burning pain, a rash or welts along the sting site, with more severe symptoms including headache, nausea and vomiting, difficulty breathing, and even heart problems [2]. The severity of the reaction depends on the type and size of the jellyfish, the victim's age, size and health (children and those in poor health can get more severe reactions), how long the stingers were on the skin and how much skin was affected [2].  

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The Hong Kong Hospital Authority does not keep statistical records of jellyfish stings [3]. Most stings are likely taken care of on-site and not reported to hospitals. The Hong Kong Poison Information Centre 2018 Annual Report notes that all types of bites and stings make up only 10% of their cases (395 reported). Of these, bees and wasps were the more common, and fewer than 50 reported "fish stings". Severe jellyfish stings are rare enough that Hong Kong hospitals do not carry jellyfish antivenom [4],  however there has been a reported case with serious consequences [5].

Some jellyfish occurrences can be predicted by accounting for environmental factors (wind, waves, etc.) that influence their movements and aggregation [6,7]. This information can be used to protect human activities and industry. 

With your help, the Hong Kong Jellyfish Project hopes to be able to gain more knowledge about jellyfish presence and the environmental or other factors that can influence their occurrence in Hong Kong waters.

Nematocyst from Cronodon.jpg

How do jellyfish sting?

Jellyfish sting by using thousands of specialized structures along their tentacles called cnidocytes. Within these structures are stinging cells called nematocysts, containing barbed tubules that can inject venom into their prey, paralyzing or killing it. A physical or chemical stimulation can trigger the nematocysts [8]. 

There is evidence that the length of the tubule within the nematocyst can determine the amount of pain felt by an unlucky swimmer. A longer tubule penetrates the human skin further and stimulates more pain receptors [9]. Jellyfish toxin is similar to bees or snakes, in that the toxins injected are a mix of multiple toxins working in concert to paralyze or kill prey [10]. Jellyfish toxins are different between species, with varying strengths, compositions and effects. This means that the necessary treatment for jellyfish stings differs across species as well [8]. The basic treatment suggestions are below.  

See a nematocyst firing in microscopic detail in this video from SmarterEveryDay

Prevention

The easiest way to prevent jellyfish stings is to avoid going into the water when jellyfish are present. Some beaches will have warnings, flags or notices posted to not enter the water. With modern technology, there are  phone apps that will send notifications of jellyfish alerts. Even if jellyfish are washed ashore, their tentacles are still capable of stinging, so avoid picking up or touching jellyfish on land. 

While swimming, wear a wetsuit or other covering that covers all limbs and the torso. As research continues into providing protection from jellyfish stings, bio-inspired options emerge. Safe sea lotion is a topical sting inhibitor that has been shown to reduce stings by up to %80 [1]. Fascinatingly, this lotion is based on the mucous coating of clownfish, who need protection from the sea anemones they live in. 

Treatment [2,8,11]

Don't pee on people you like! There is a popular misconception that jellyfish stings can be treated by urinating on them. This is not correct and isn't sanitary (it is a myth that human urine is "sterile"). In truth, different jellyfish stings have different treatments and there is no single treatment for all types of stings. Because of the variety of jellyfish and the lack of controlled studies on their stings, most sting management techniques have weak evidence and require further research.

Much of jellyfish sting care involves pain management and preventing further stings.

DO:

  • Get out of the water to get away from the jellyfish and prevent further stings.

  • Wash the area in sea water to clean off tentacles. Using a vinegar solution (4%–6% acetic acid) can deactivate some nematocysts, though this will not work for all species!.

  • Remove any stinging cells that remain on the skin using tweezers. Some organizations recommend a hard-edged object like a credit card, but others say the pressure can activate more nematocysts increasing the pain level. 

  • A hot water soak (hot, not scalding!) up to 20 minutes to help deactivate some types of venom. Smaller stings or other       types of stings may use a cold pack for pain management. 

  • The Hong Kong Hospital Authority says that medical professionals decide case-by-case whether to use a topical pain reliever or anti-inflammatory to reduce the pain of the sting and an antihistamine to control swelling. 

DON'T:

  • Do not rub the affected area with a towel or use fresh water to remove, as these actions may cause more nematocysts to   fire, injecting more venom. 

  • Do not use a pressure immobilization bandage on the affected area. That may cause more venom to be injected. 

  • Other home remedies like baking soda, meat tenderizer and alcohol either will not work or will make the problem worse.  

In case of severe reactions, immediately seek advanced medical care! In some hospitals, antivenin is available, though it is species-specific and not available in Hong Kong. 

References:

1. Boulware, D. R. (2006). A Randomized, Controlled Field Trial for the Prevention of Jellyfish Stings With a Topical Sting Inhibitor. Journal of Travel Medicine, 13(3), 166–171. https://doi.org/10.1111/j.1708-8305.2006.00036.x

2. Mayo Clinic. (2020). Jellyfish stings—Symptoms and causes. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/jellyfish-stings/symptoms-causes/syc-20353284. 

3. Hospital Authority. Access to Information request. Personal communication. December 24, 2020. 

4. Chan, Y. (2013). Marine Envenomation. The Hong Kong Medical Diary, 18(3), 36.

5 Lam, S. C., Hung, Y., Chow, E. C., Wong, C. W., Tse, W., & Ho, P. (2014). Digital ischaemia: A rare but severe complication of jellyfish sting. Hong Kong Medical Journal, 20(5), 460–463. https://doi.org/10.12809/hkmj134155

6. Aouititen, M., Bekkali, R., Nachite, D., Luan, X., & Mrhraoui, M. (2019). Predicting Jellyfish Strandings in the Moroccan North-West Mediterranean Coastline. European Scientific Journal ESJ, 15. https://doi.org/10.19044/esj.2019.v15n2p72

7. Gershwin, L., Lewis, M., Gowlett-Holmes, K. L., & Kloser, R. J. (2014). The Medusae. In: Pelagic Invertebrates of South-Eastern Australia: A field reference guide. (Version 1.1).

8. Lakkis, N., Maalouf, G. J., & Mahmassani, D. (2015). Jellyfish Stings: A Practical Approach. Wilderness and Environmental Medicine, 26(3).

9. Kitatani, R., Yamada, M., Kamio, M., & Nagai, H. (2015). Length Is Associated with Pain: Jellyfish with Painful Sting Have Longer Nematocyst Tubules than Harmless Jellyfish. PLoS ONE, 10(8). https://doi.org/10.1371/journal.pone.0135015

10. ScienceDaily. (2020). What makes a giant jellyfish’s sting deadly? ScienceDaily. https://www.sciencedaily.com/releases/2020/06/200610120958.htm

11. Cegolon, L., Heymann, W. C., Lange, J. H., & Mastrangelo, G. (2013). Jellyfish Stings and Their Management: A Review. Marine Drugs, 11(2), 523–550. https://doi.org/10.3390/md11020523