### Human:\nwhy does my anus only itch at night ( 20 years old male)? . for the past week around evening time i feel extreme itching goes away after a few hours. starts again the next day at the same time\n\n### Assistant: you could have pinworms. the live in your rectum and come out at night (don't ask me how they know it is night! ) and lay eggs around your anal ring. this is one common cause of "pruritis ani" (latin for "itchy anus"). you will need to have your medical provider order a pinworm test. if this is not the cause then you will need to see your medical provider for an exam to see if their are other treatable reasons.