The night-time itch: Understanding pinworm infection

Introduction 

Pinworm infection or Enterobiasis is a common cause of night-time perianal itching, especially  in children. It is caused by Enterobius vermicularis, also known as pinworm. It is one of the  most common helminth infections worldwide, affecting around one billion people. It  commonly occurs among pre-school and school-going children, institutionalized persons and  household members of those with pinworm infection.  

Habitat and transmission 

Humans are the only hosts of pinworms and the worms inhabit the large intestine, mainly the  caecum and appendix. Pinworm infection transmitted via the faeco-oral route: mainly by  ingestion of infective eggs on contaminated hands and fomites. As the eggs are very small and  float in air, rarely infection may occur through inhalation of eggs as well.  

Pathophysiology and life cycle  

The adult female lays eggs in perianal folds of humans. Infection occurs though eggs which  are transferred to the mouth via hands that have scratched the perianal area or exposed to eggs  on fomites such as bed linen and furniture. The eggs are hatched in the small intestine and  larvae turn into adults and live in the caecum. The adult gravid female migrates to the anus at  night and deposits eggs in the perianal skin. The eggs become infective in about four to six  hours. These eggs will contaminate hands or fomites. The eggs also may hatch and larvae can  migrate into rectum through anal skin, giving rise to retro-infection. 

Clinical manifestations 

Often asymptomatic, the most common symptom is perianal itching which occurs due to  irritation of perianal skin caused by eggs and larvae. This may lead to disturbed sleep at night,  irritability, perianal excoriation, sometimes complicated by secondary bacterial infection.  Rarely, worms may migrate to perianal region and give rise to vulvo-vaginitis, urinary tract  infections and pelvic or peritoneal granulomas.  

Diagnosis 

Microscopic identification of eggs collected using an adhesive cellulose tape or paddle placed  in perianal area early morning before defecation is the mainstay of laboratory diagnosis. Seeing  adult worms in perianal area is also diagnostic. As eggs are not usually seen in stools, stool  examination is not recommended.  

Treatment and prevention 

Mebendazole, pyrantel pamoate, and albendazole are used for treatment. Either of these three  drugs can be given as a single dose, and another single dose 2 weeks later. All household  members need to be treated at once. Good hygienic practices are essential to prevent spread  and reinfection. Bed-linen and clothes should be washed in hot water and dried in direct sun  light. Infected persons should change underclothes and bed linen each morning and shower to  remove eggs on clothes and skin. Hand washing using warm water and soap after using the  toilet, changing diapers and before handling food is an important measure. Fingernails should  be cut short and nail biting should be avoided. Children should be taught the importance of  washing their hands to prevent infections. 

Conclusion 

Although pinworm infection is usually mild and doesn’t cause serious morbidity, recognizing  its characteristic symptoms and ensuring proper treatment of all household members are key to  preventing reinfection and controlling its spread. 

References 

CDC - DPDx - Enterobiasis n.d. https://www.cdc.gov/dpdx/enterobiasis/index.html (accessed  April 3, 2026). 

Rojelio Mejia, Jill Weatherhead, and Peter J. Hotez. Intestinal Nematodes (Roundworms).  Principles and practice of infectious diseases. 9th edition, ELSEVIER; 2020, p. 3439.

Assessed and Endorsed by the MedReport Medical Review Board