Print OverviewJellyfish stings are fairly common problems for people swimming, wading or diving in oceans. The long tentacles trailing from the jellyfish can inject venom from thousands of microscopic barbed stingers. Most often jellyfish stings cause instant pain and inflamed marks on the skin. Some stings may cause more whole-body (systemic) illness. And in rare cases they're life-threatening. Most jellyfish stings get better over a few days or weeks with home treatment. Severe reactions likely need emergency medical care.Products & ServicesA Book: Mayo Clinic Family Health BookNewsletter: Mayo Clinic Health Letter — Digital EditionShow more products from Mayo Clinic SymptomsSymptoms of jellyfish stings include: Burning, prickling, stinging pain Welts or tracks on the skin — a "print" of the tentacles' contact with the skin Itchiness (pruritus) Swelling Throbbing pain that radiates up a leg or an arm Severe jellyfish stings can affect multiple body systems. These reactions may appear rapidly or several hours after the stings. Symptoms of severe jellyfish stings include: Stomach pain, nausea and vomiting Headache Muscle pain or spasms Faintness, dizziness or confusion Difficulty breathing Heart problems The severity of a reaction depends on: The type and size of the jellyfish The age, size and health of the person affected, with severe reactions more likely in children How long the person was exposed to the stingers How much of the skin is affected When to see a doctorSeek emergency treatment if you have severe symptoms. See your health care provider if your symptoms worsen or the wound shows symptoms of infection. Request an appointment CausesJellyfish stings are caused by brushing against a jellyfish tentacle. Tentacles have thousands of microscopic barbed stingers. Each stinger has a tiny bulb that holds venom and a coiled, sharp-tipped tube. When you brush against a tentacle, tiny triggers on its surface release the stingers. The tube pierces the skin and releases venom. It affects the area of contact and may enter the bloodstream. Jellyfish that have washed up on a beach may still release venomous stingers if touched. Types of jellyfishMany types of jellyfish are fairly harmless to humans. Others can cause severe pain and a full-body (systemic) reaction. These jellyfish cause more-serious problems in people: Box jellyfish. Box jellyfish can cause intense pain and, rarely, life-threatening reactions. The more dangerous species of box jellyfish are in the warm waters of the Pacific and Indian oceans. Portuguese man-of-war. Also called bluebottle jellyfish, Portuguese man-of-war jellyfish live mostly in warmer seas. This type has a blue or purplish gas-filled bubble that keeps it afloat. Sea nettle. Common in both warm and cool seawaters. Lion's mane jellyfish. These are the world's largest jellyfish, with a body diameter of more than 3 feet (1 meter). They're most common in cooler, northern regions of the Pacific and Atlantic oceans. Risk factorsConditions that increase the risk of jellyfish stings: Swimming when jellyfish appear in large numbers (a jellyfish bloom) Swimming or diving in jellyfish areas without protective clothing Playing or sunbathing where jellyfish are washed up on the beach Swimming in a place known to have many jellyfish ComplicationsPossible complications of a jellyfish sting include: Delayed skin reaction, causing blisters, rash or other irritation Irukandji syndrome, which causes chest and stomach pain, high blood pressure, and heart problems PreventionThe following tips can help you avoid jellyfish stings: Wear a protective suit. When swimming or diving in areas where jellyfish stings are possible, wear a wet suit or other protective clothing. Diving stores sell protective "skin suits" or "stinger suits" made of thin, high-tech fabric. Consider protective footwear, as stings can also occur while wading in shallow water. Get information about conditions. Talk to lifeguards, local residents or officials with a local health department before swimming or diving in coastal waters, especially in areas where jellyfish are common. Avoid water during jellyfish season. Stay out of the water in jellyfish areas when jellyfish numbers are high. By Mayo Clinic Staff Request an appointment Diagnosis & treatment May 14, 2024 Print Show references Tintinalli JE, et al. Marine trauma. In: Tintinalli's Emergency Medicine: A Comprehensive Study Guide. 9th ed. McGraw Hill; 2020. http://accessmedicine.mhmedical.com. Accessed April 28, 2022. Cegolon L, et al. Jellyfish stings and their management: A review. Marine Drugs. 2013; doi:10.3390/md11020523. Briggs JK. Bites, marine animal. In: Triage Protocols for Aging Adults. Wolters Kluwer; 2019. Li L, et al. Interventions for the symptoms and signs resulting from jellyfish stings. Cochrane Database of Systematic Reviews. 2013; doi:10.1002/14651858.CD009688.pub2/abstract. Ward NT, et al. Evidence-based treatment of jellyfish stings in North America and Hawaii. Annals of Emergency Medicine. 2012; doi:10.1016/j.annemergmed.2012.04.010. Auerbach PS. In reply to evidence-based treatment of jellyfish stings in North America and Hawaii. Annals of Emergency Medicine. 2013; doi:10.1016/j.annemergmed.2012.07.128. Marine envenomations: Jellyfish & hydroid stings. Divers Alert Network. https://dan.org/alert-diver/article/marine-envenomations-jellyfish-hydroid-stings/. Accessed April 28, 2022. Hornbeak KB, et al. Marine envenomation. Emergency Medicine Clinics of North America. 2017; doi:10.1016/j.emc.2016.12.004. Lakkis NA, et al. Jellyfish stings: A practical approach. Wilderness & Environmental Medicine. 2015; doi:org/10.1016/j.wem.2015.01.003. Marcus EN, et al. Jellyfish stings. https://www.uptodate.com/contents/search. Accessed April 28, 2022. 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