• Intestinal infection with Enterobius vermicularis
    • Characterized by perineal and perianal itching
    • Usually worse at night
  • System(s) affected: gastrointestinal; skin/exocrine
  • Synonym(s): enterobiasis


Predominant age: 5 to 14 years


  • Most common helminthic infection in the United States
    • 20 to 42 million people harbor the parasite.
  • ~30% of children are infected worldwide.

Pediatric Considerations
More common in children, who are more likely to become reinfected

Etiology and Pathophysiology

  • Small white worms (2 to 13 mm) inhabit the cecum, appendix, and adjacent portions of the ascending colon following ingestion; associated with multiple case reports of appendicitis
  • Female worms migrate to the perineal areas at night to deposit eggs; this causes local irritation and itching.
  • Scratching leads to autoingestion of the eggs and continuation of pinworm’s life cycle within the host. Eggs incubate 1 to 2 months in the host small intestine. When mature, female pinworms migrate to the colon where they lay eggs around the anus at night, and the lifecycle continues.
  • Infestation by the intestinal nematode E. vermicularis (1)

Risk Factors

  • Institutionalization (prevalence >50%)
  • Crowded living conditions
  • Poor hygiene
  • Warm climate
  • Handling of infected children’s clothing or bedding

General Prevention

  • Hand hygiene, especially after bowel movements
  • Clip and maintain short fingernails.
  • Wash anus and genitals at least once a day, preferably during shower.
  • Avoid scratching anus and putting fingers near nose (pinworm eggs can also be inhaled) or mouth.

Commonly Associated Conditions

  • Pruritus ani
  • Appendicitis

There's more to see -- the rest of this topic is available only to subscribers.