Accidentally swallowing or breathing in pinworm eggs causes a pinworm infection. The tiny (microscopic) eggs can be carried to your mouth by contaminated food, drink or your fingers. Once swallowed, the eggs hatch in the intestines and mature into adult worms within a few weeks.

How does a person get pinworms?

Pinworm infection is spread by the fecal-oral route, that is by the transfer of infective pinworm eggs from the anus to someone's mouth, either directly by hand or indirectly through contaminated clothing, bedding, food, or other articles.

Why do pinworms exist?

The cause of a pinworm infection is the worm Enterobius vermicularis. The entire lifecycle – from egg to adult – takes place in the human gastrointestinal tract of a single human host. This process is two to eight weeks.