Derm

Swimmer's Itch

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Swimmer's Itch, Cercarial Dermatitis

  • Pathophysiology
  1. Predominately fresh water exposure
    1. Distribution
      1. Northern United States
      2. Canada
    2. Episodic outbreaks related to snail maturation
      1. Bright, warm days of summer induce snail shedding
      2. Most outbreaks occur near shore
  2. Inflammatory reaction to parasitic cercariae (larvae)
    1. Carriers: Snails
    2. Organisms
      1. Non-human schistosomes (parasitic flatworm)
      2. Flukes
    3. Mechanism
      1. Larvae penetrate Epidermis with water evaporation
      2. Larvae die once embedded
      3. Inflammatory reaction depends on sensitization
  • Symptoms and symptoms
  1. Areas affected limited to exposed areas
  2. Initial Pruritus from Acute Urticarial reaction
    1. Pruritus within 1 hour (minimal to intense)
  3. Later papular eruption occurs
    1. First Exposure
      1. Papules within 5 to 13 days
    2. Subsequent Exposure (Sensitized)
      1. Pruritic Papules within hours
      2. Symptoms peak within 2-3 days
      3. Resolution within 7 days
  • Differential Diagnosis
  1. Seabather's Eruption (limited to bathing suit area)
  2. Aquagenic Pruritus
  1. Antihistamines
  2. Cool compresses
  3. Sarna or Calamine lotion
  4. Low to medium potency Topical Corticosteroids
  • Complications
  1. Secondary infection related to excoriation
  • Prevention
  1. Dry Skin immediately after bathing
  • Course
  1. Lesions clear completely in 1 to 2 weeks
  • References
  1. Habif (1996) Clinical Dermatology, 3rd ed, Mosby, 486
  2. Mulvihill (1990) Cutis 46:211-3 [PubMed]
  3. Pharis (1997) J Am Acad Dermatol 36:448-59 [PubMed]