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Warm water hazard

Sea lice and seabather's eruption

Quail, Myles Thomas MSEd, RN, LNC

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doi: 10.1097/01.NURSE.0000549726.99691.05
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DURING THE COLD WINTER MONTHS, thousands of vacationers travel to beaches in warm climates. ED nurses often see patients who have recently returned from these tropical climates complaining of a severe pruritic dermatitis caused by exposure to jellyfish larvae known colloquially as sea lice (see What's in a name?).

Like beachgoers, many healthcare professionals are unfamiliar with this disorder, even though it was described as early as 1949.1 A localized rash is the most common sign of exposure but some patients, particularly children, experience more serious signs and symptoms such as fever, chills, headaches, and nausea/vomiting.

This article reviews the dermatologic disorder associated with sea lice exposure, known correctly as seabather's dermatitis (SBE), and discusses assessment tips, nursing care, and patient teaching.

Stinging structures

SBE occurs when microscopic marine-life larvae become trapped in a bather's swimwear webbing or elastic band as the bather exits the ocean. The larvae have stinging structures (nematocysts) that discharge a toxin into the bather's skin (see Tiny creatures deliver a sting). Bathers initially do not feel the nematocyst discharge; signs and symptoms typically appear within a few hours to a day after the exposure. In addition, secondary exposure can occur days to weeks later when infested swimwear that was hand-washed and air-dried is reworn.1,2

A history of ocean exposure leading to development of dermatitis within 24 hours after the exposure is the key diagnostic indicator for SBE, although signs and symptoms may be delayed for up to 30 days after exposure in some cases.3 The patient initially complains of urticaria or rash that is erythematous and intensely pruritic, especially at night when it causes insomnia. The rash appears only where the skin was covered with a bathing or wet suit. In some cases, 200 or more stings may be visible in these areas.1,3 The duration of irritation averages around 7 days, but secondary infection may result from intense scratching.1,4

At higher risk are bathers or surfers who wear a one-piece bathing suit, wet suit, or T-shirt because the garments entrap and hold the larvae against a larger surface area. Long hair is also problematic because the nematocysts attach to the hair as the bather exits the ocean. Children are especially susceptible to developing a significant rash because they repeatedly enter and leave the ocean during play.1,3

Fewer than 10% of patients with SBE experience systemic effects such as abdominal cramping, arthralgia, chills, conjunctivitis, diarrhea, dyspnea, fatigue, fever, headache, lethargy, malaise, muscle spasms, nausea, sneezing, and vomiting.1,2 Some of these effects may be due to the ingestion of infected seawater or a systemic immune response. Children are more likely to have febrile reactions than adults.1-3

Nursing assessment

The triage nurse must first isolate and triage the patient away from other patients. Although SBE is not contagious, all rashes must be examined to rule out a communicable disease.

Immediately assess the patient for signs and symptoms of a serious allergic reaction. Assess and support the patient's ABCs and obtain vital signs, including temperature.

When obtaining a health history, ask about the patient's recent travel history, especially recent ocean exposure. Also document the onset of signs and symptoms; location, duration, and characteristics of lesions; associated, aggravating, and relieving factors; and any treatments and response to treatment. Ask the patient to describe how the rash looked at first and whether it has spread or changed in appearance.5

Also assess for possible alternative causes for the rash, such as recent medication changes or newly prescribed medications; use of new detergent products, soaps, or shampoos; recent illness or immunizations; and exposure to pets or other animals. Ask if any other family members are affected.5

Physical assessment includes visual inspection and palpation of the skin. Assess the rash to determine the following:5

  • type of lesion
  • morphology of individual lesions
  • configuration of multiple lesions (such as scattered, grouped, or linear)
  • distribution of lesions
  • color, consistency, and feel of lesions.

In SBE, lesions are inflammatory papules that often become vesicular or pustular. The distribution of lesions matches areas covered by a bathing suit, wet suit, or points of pressure, such as the wristbands of diving suits.5,6

Nursing interventions

Treatment for SBE is symptomatic; skin lesions typically resolve spontaneously within 2 weeks. The standard regimen is a combination of oral antihistamines, topical antipruritic agents such as calamine lotion, and topical corticosteroids. Oral corticosteroids may be prescribed in severe cases.1,4,7

A secondary bacterial infection may occur due to a patient's intense scratching. Purulent lesions that do not resolve require further medical attention. Bathers and surfers who reexpose themselves to contaminated oceans may have multiple episodes of SBE requiring systemic treatment with oral corticosteroids and/or hospitalization.1,4,7

Discharge instructions should reinforce the treatment recommended by the clinician, including teaching the patient about the appropriate use of prescribed medication and possible adverse reactions the patient should report. Teach the patient to observe for any increase in rash area, to avoid scratching, and to monitor for signs and symptoms of infection. Tell the patient to call the primary care provider if signs and symptoms persist beyond 2 weeks.

Prevention and patient teaching

Public beaches raise warning flags or post signage at their entrances to alert bathers and surfers of specific ocean conditions and hazards (private beaches usually do not post signage). A purple flag and/or sign indicates dangerous marine life in the ocean. Teach patients to check for any such signage before bathing in the ocean and to heed warnings.

Clothing is another important factor in SBE prevention. Teach women that wearing two-piece bathing suits reduces the risk, and advise all bathers to avoid wearing T-shirts in the water. If possible, bathers should immediately remove their wet suit after leaving the ocean and before showering, because fresh water may cause nemocytes to discharge. Inform patients that multiple machine washings with hot water and detergent may be needed to rid the swimwear of all the nematocysts.2,8,9

Immediately removing contaminated suits and showering is the best defense against SBE. Evidence indicates that strategies such as towel drying, showering with very hot or very cold water, and applying lotion or ointments after a shower do not prevent SBE because by then, the nematocysts have already discharged toxin into the skin.6

As the season for tropical beach vacations progresses, nurses should become familiar with SBE and its classic presentation. Teaching patients about preventive measures will make for a safer and more enjoyable vacation.

Tiny creatures deliver a sting

The larvae most commonly implicated in SBE are released by “thimble jellyfish” (Linuche unguiculata); however, larvae from other species such as corals, hydroids, and sea anemones such as Edwardsiella lineata may also cause SBE.2 Larvae are most likely to appear in warm ocean waters from March until August, depending on the species and territorial region.8,9

As a defense mechanism, thimble jellyfish larvae have hundreds of stinging structures (nematocysts) that discharge an irritating toxin into the bather's skin.2 Discharges occur due to mechanical pressure when the bathing suit drains and the larvae rub against the bather's skin. Discharges may also occur from osmotic changes from evaporation or when the bather rinses off a bathing suit with fresh water or sits in a wet suit.2,9

Accounts of sea lice exposure have been increasing over the last few years, with reports from Florida, the Bahamas, Bermuda, Brazil, Caribbean Islands including Cuba and Puerto Rico, Mexico, New Zealand, Philippines, and Papua New Guinea. Although most reports are from tropical and subtropical waters, epidemic episodes have transpired as far north as Long Island, New York.8,9

What's in a name?2,9

In the context of SBE, “sea lice” is a misnomer. The culprits causing SBE are not lice at all; rather, they are larvae of the thimble jellyfish and other sea creatures. Other terms used to describe SBE include beach lice, diver's dermatitis, ocean itch, and pica-pica.


1. Rossetto AL, Da Silveira FL, Morandini AC, Haddad V, Resgalla C. Seabather's eruption: report of fourteen cases. An Acad Bras Cienc. 2015;87(1):431–436.
2. Rademaker M. Sea bather's eruption. DermNet NZ. 2014.
3. Russell MT, Tomchik RS. Seabather's eruption, or “sea lice”: new findings and clinical implications. J Emerg Nurs. 1993;19(3):197–201.
4. Freudenthal AR, Joseph PR. Seabather's eruption. N Engl J Med. 1993;329(8):542–544.
5. Goldstein BG, Goldstein AO. Approach to dermatologic diagnosis. UpToDate. 2018.
6. Wilson ME. Skin lesions in the returning traveler. UpToDate. 2017.
7. Marcus EN, Isbister GK. Jellyfish stings. UpToDate. 2016.
8. Brown CW Jr. Seabather's eruption treatment and management. Medscape. 2018.
9. Prohaska J, Tanner LS. Seabathers Eruption. StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2018.

dermatitis; diver's dermatitis; SBE; sea lice; seabather's eruption

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