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Clinical Summary

Marine dermatitis, also known as “sea bather’s eruption,” is a pruritic condition commonly mislabeled as sea lice. Symptoms usually occur a few minutes to 12 hours after exposure. The offending organisms are probably numerous and include the larval form of the thimble jellyfish and the planula form of the sea anemone, Edwardsiella lineata. The rash consists of erythematous wheals and papules, which may be extremely itchy. Systemic manifestations include fever, malaise, headache, conjunctivitis, and urethritis. Unlike cercarial dermatitis, marine dermatitis primarily affects areas of the body covered by caps, fins, and bathing suits.

FIGURE 16.117

Marine Dermatitis. Typical appearance of marine dermatitis. (Photo contributor: Richard A. Clinchy III, PhD.)

FIGURE 16.118

Cercarial Dermatitis. The discrete and highly pruritic papules of schistosome cercarial dermatitis commonly occur on exposed body areas. (Photo contributor: Edgar Maeyens, MD. Reproduced with permission from Auerbach PS, Cushing TA, Harris NS, eds. Auerbach’s Wilderness Medicine, 7th ed. Philadelphia, PA: Elsevier; 2017. Copyright © Elsevier.)

Cercarial dermatitis, or “swimmer’s itch,” occurs when humans become accidental hosts of schistosomes that usually infect nonhuman hosts. This causes an immune response, resulting in itching, erythema, and mild edema. After 60 minutes, the classic signs are red macules that later become pruritic papules 3 to 5 cm in diameter and surrounded by erythema.

Management and Disposition

Marine dermatitis is self-limited, rarely persisting beyond 2 weeks. The dermatitis may be partially prevented by a vigorous soap-and-water scrub after saltwater bathing. Treatment is symptomatic. Calamine lotion with 1% menthol may bring relief. Topical steroids may provide additional relief. In severe cases, oral antihistamines and corticosteroids may be necessary.

Cercarial dermatitis is treated with isopropyl alcohol or calamine lotion. Severe cases may require systemic corticosteroids, while bacterial infection may require topical or oral antibiotics.


  1. Marine dermatitis primarily affects areas covered by caps, fins, and bathing suits.

  2. During late spring and summer, incidence increases along the US east coast. In one reported outbreak, 25% of individuals entering the water were affected.

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