Adult pinworms live in the intestine and colon. At night, the female adult worms deposit their eggs outside the rectum or anal area.
One way to diagnose pinworms is to shine a flashlight on the anal area. The worms are tiny, white, and threadlike. If none are seen, check for two or three additional nights.
The best way to diagnose this infection is to do a tape test. The best time to do this is in the morning before bathing, because pinworms lay their eggs at night. Firmly press the sticky side of a 1-inch strip of cellophane tape over the anal area for a few seconds. The eggs stick to the tape. The tape is then transferred to a glass slide, sticky side down. Your health care provider needs to examine the slide to confirm that there are eggs.
The tape test may need to be done on three separate days to improve the chances of detecting the eggs.