Pruritus ani

Pruritus ani is the irritation of the skin at the exit of the rectum, known as the anus, causing the desire to scratch. The intensity of anal itching increases from moisture, pressure, and rubbing caused by clothing and sitting. At worst, anal itching causes intolerable discomfort that often is accompanied by burning and soreness.

Causes
Anal itching can be caused by irritating chemicals in the foods we eat, such as are found in spices, hot sauces, and peppers. It also can be caused by the irritation of frequent liquid stools, diarrhea, or escape of small amounts of stool (incontinence). Another main cause is yeast infection or Candidiasis.

Some diseases increase the possibility of yeast infections, such as diabetes mellitus or HIV infection. Treatment with antibiotics can lead to a yeast infection and irritation of the anus. Psoriasis also can irritate the anus. Abnormal passageways (fistulas) from the small intestine or colon to the skin surrounding the anus can form as a result of disease (such as Crohn's disease), and these fistulas bring irritating fluids to the anal area. Other problems that can cause anal itching include pinworms, hemorrhoids, tears of the anal skin (fissures), and skin tags (abnormal local growth of anal skin).

Prurido anal