Background: Seabather's eruption (SE) is a highly pruritic eruption under swimwear that occurs after bathing in the ocean. Its cause has been unknown. Few data have been collected since the classic description by Sams in 1949.
Objective: Our purpose was to describe the clinical and histopathologic findings in SE and to confirm the cause.
Methods: Patients with a pruritic eruption that developed after swimming were seen within 1 week of onset. Skin biopsy specimens and sera were obtained in selected cases. Water samples taken from areas of active SE outbreaks were examined for a causative organism. Sera were tested by enzyme-linked immunosorbent assay for reactivity to this organism.
Results: In southeast Florida, during a 4-month period, 70 patients with SE were seen. Inflammatory papules and pruritus were noted within hours of exposure. Eruptions were maximal in areas covered by a bathing suit. Children were more likely than adults to have systemic symptoms. The average duration of the eruption and pruritus was 12.5 days, with recurrences in 4.3% of patients. Histopathologic examination revealed a superficial and deep perivascular and interstitial infiltrate consisting of lymphocytes, neutrophils, and eosinophils. Water samples contained many cnidarian larvae, later grown to maturity and identified as Linuche unguiculata (thimble jellyfish). Enzyme-linked immunosorbent assay demonstrated in patients' sera high IgG levels specific for L. unguiculata.
Conclusion: SE is a severely pruritic marine dermatosis that resolves spontaneously within 2 weeks. Therapy is symptomatic but often ineffective. Sera from affected persons showed specific reactivity to L. unguiculata.