gastrointestinal disorders
Pruritus Ani (Anal Itching)
Etiology of Pruritus Ani
Most anal itching is Idiopathic (the majority) Hygiene-related Too little cleansing leaves irritating stool and sweat residue on the anal skin. Too much cleansing, often with sanitary wipes and strong soaps, can be drying or irritating or occasionally cause a contact hypersensitivity reaction. Large external Hemorrhoids can make postdefecation cleansing difficult, and large internal hemorrhoids can cause mucus drainage or fecal soilage and consequent irritation. Other distinct causes are rarely identified, but a variety of factors have been implicated (see table). In the very young and old, fecal and urinary incontinence predispose to local irritation and secondary candidal infections. Once itching occurs, resulting from any cause, an itch-scratch-itch cycle can begin, in which scratching begets more itching. Often, skin becomes excoriated and secondarily infected, causing yet more itching. Also, topical treatments for itching and infection may be sensitizing, causing further itching. 