Do pinworms usually cause your rectum to bleed?

Not the worms: Pinworm infection is caused by enterobius vermicularis a small, white worm w/ pointed tail. In humans, they reside in the lower colon. Typically asymptomatic or cause perianal itching. The tiny worms are not invasive and do not cause rectal bleeding. Severe irritation from aggressive scratching could be source of local, minimal bleeding but is unlikely.