Can someone explain to me how come my anus is itching?

Anal itching: Dietary factors and fecal soilage account for the majority of patients with anal itching, or pruritus. Coffee, cola, beer, tea, tomatoes, and citrus fruits are some possible dietary irritants. Other less common causes include anorectal diseases (hemorrhoids, fistulas, fissures), infections (including sexually-transmitted ones), or skin diseases, such as psoriasis.