The phenomenon of itching in the anus every night is mostly caused by perianal diseases and systemic lesions, and the specific causes include the following: 1. itching symptoms caused by parasitic infections, especially pinworm disease, pinworm disease is an intestinal parasite, especially at night, often crawl out of the anus, around the anus, thus causing itching symptoms. 2. itching symptoms caused by hemorrhoids . The symptoms of hemorrhoids are mainly caused by the occurrence of varicose veins around the anus, which can form many thrombi or venous blood clusters around the anus, which are stimulated by intestinal fluids at night, thus causing itching and even painful symptoms. 3, itchy symptoms caused by anal eczema. The skin around the anus will have eczema-like changes.