Cause

Pinworm infections are usually caused by swallowing the eggs of the pinworm (Enterobius vermicularis) after coming in contact with an infected person or with an object that has eggs on its surface. Infection can also be spread when a person inhales airborne eggs, but this is rare. In rare cases, pinworm infection persists because eggs hatch outside the anus and the young worms crawl back inside the body.