Pinworms get into the body when people ingest or breathe in the microscopic pinworm eggs. These eggs are light and float in the air and can be found on contaminated hands and surfaces, such as:
The eggs pass into the digestive system and hatch in the small intestine. From the small intestine, pinworm larvae go to the large intestine, where they live as parasites (with their heads attached to the inside wall of the bowel).
About one to two months later, adult female pinworms leave the large intestine through the anus (the opening where bowel movements come out). They lay eggs on the skin right around the anus, which triggers itching in that area, usually at night.
When someone scratches the itchy area, microscopic pinworm eggs transfer to their fingers. Contaminated fingers can then carry pinworm eggs to the mouth, where they go back into the body, or stay on various surfaces, where eggs can survive for two to three weeks.
Fortunately, most eggs dry out within 72 hours. In the absence of host autoinfection, infestation usually lasts only four to six weeks.
