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Seabather's eruption in Adult
Other Resources UpToDate PubMed

Seabather's eruption in Adult

Contributors: David O'Connell MD, Robert Norris MD, Joanne Feldman MD, MS, Susan Burgin MD
Other Resources UpToDate PubMed


Seabather's eruption is caused by envenomation by and subsequent hypersensitivity to the larval form of marine coelenterates encountered in seawater. Larvae of the thimble jellyfish, Linuche unguiculata, are the cause of eruptions in the Atlantic Ocean off the southeastern coastline of Florida, Mexico, and the Caribbean. It has also been noted to occur in the Philippines and other areas of coastal Southeast Asia with Linuche aquila as the causative organism. While the adult jellyfish measures 5-20 mm (up to 3/4 inch), the larval form is only 0.5 mm. Off the coast of the mid-Atlantic up through New York, the larvae of the sea anemone Edwardsiella lineata have also been identified as causal. Most cases occur between March and August.

Some refer to seabather's eruption as "sea lice," although this is a misnomer, as true sea lice are skin parasites of fish that do not affect humans.

Envenomation, primarily triggered by pressure and friction, occurs when the larvae get caught beneath swimwear and stinging cells (nematocysts) discharge into the skin.

The condition typically presents within minutes to 1-2 days after patient emerges from seawater as a pruritic, urticarial, and/or papular rash in the distribution of their bathing suit or other areas of pressure including surfboard contact. Symptoms usually persist for 5-7 days but may persist for up to 2 weeks or longer. Some patients may develop fever, headache, malaise, and emesis (especially children). Conjunctivitis and urethritis may develop if exposure to those mucous membranes occurs. Systemic hypersensitivity reactions, including anaphylaxis, are rare in jellyfish envenomations. Rarely, the rash may recur within 2 weeks, and atopic individuals may have lesions for up to 6 weeks.

Risk factors include age younger than 16 years, a past history of seabather's eruption, and surfing. Showering without a bathing suit after seawater exposure has been found to be protective. Having a history of seabather's eruption increases the risk of future episodes, which supports the theory that this condition is due to underlying hypersensitivity. Some individuals are apparently immune, however, and do not develop a rash despite similar, repeated exposures in the same seawater as those who are symptomatic. No deaths have been reported.


T63.691A – Toxic effect of contact with other venomous marine animals, accidental, initial encounter

238534006 – Sea bather's eruption

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Differential Diagnosis & Pitfalls

  • Pseudomonas folliculitis – Also called hot tub folliculitis, may also be accentuated under swimwear.
  • Patients with swimmer's itch (animal schistosomes) have lesions outside the bathing suit area.
  • Seaweed dermatitis is more severe and leads to blistering and desquamation; it is also endemic to Hawaii, where seabather's eruption has not been reported.
  • "Dogger Bank itch" (Bryozoa dermatitis) is an algae-induced seaweed dermatitis. This condition is found in dockworkers along the North Sea and the Mediterranean. The lesions are chronic and can be disabling.
  • Rashes caused by other ocean-dwelling organisms (hydromedusae, crab larvae)
  • Acute schistosomiasis – Heavy exposure to human schistosomes may result in acute schistosomiasis, which may be associated with urticarial rash, pruritus, limb edema, lymphadenopathy, fever, nausea, and diarrhea.
  • Varicella
  • Scabies
  • Contact dermatitis
  • Folliculitis
  • Insect bites
  • Urticaria
  • Mite dermatitis – Oak mite bites occur in the US Midwest; neck and torso bites may resemble seabather's eruption.

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Last Reviewed:06/18/2019
Last Updated:01/09/2020
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Patient Information for Seabather's eruption in Adult
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Seabather's eruption in Adult
A medical illustration showing key findings of Seabather's eruption : Primarily truncal distribution, Surfer, Pruritus, Ocean swimming, Wheal, Smooth papules, Bathing suit distribution
Clinical image of Seabather's eruption - imageId=253952. Click to open in gallery.  caption: 'Myriads of erythematous papules on the trunk (areas that were beneath a bathing suit).'
Myriads of erythematous papules on the trunk (areas that were beneath a bathing suit).
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