Anal Itching: A Merck Manual of Patient Symptoms podcast
The perianal skin tends to itch, which can result from numerous causes (see Table 1: Some Causes of Pruritus Ani). This condition is also known as pruritus ani. Occasionally, the irritation is misinterpreted by the patient as pain, so other causes of perianal pain (eg, abscess) should be ruled out.
Most anal itching is
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 Some Causes of Pruritus Ani).
In the very young and elderly, fecal and urinary incontinence predisposes 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.
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History of present illness should note whether the problem is acute or recurrent. The patient should be asked about topical agents applied to the anus, including wipes, ointments (even those used to treat itching), sprays, and soaps. Diet and drug profiles should be reviewed for causative agents (see Table 1: Some Causes of Pruritus Ani), particularly acidic or spicy foods. A general sense of hygiene should be obtained by asking about frequency of showers and baths.
Review of systems should seek symptoms of causative disorders, including urinary or fecal incontinence (local irritation), anal pain or lump, blood on toilet paper (hemorrhoids), bloody diarrhea and abdominal cramps (inflammatory bowel disease), and skin plaques (psoriasis).
Past medical history should identify known conditions associated with pruritus ani, particularly prior anorectal surgery, hemorrhoids, and diabetes.
General examination should obtain a sense of overall hygiene and note any signs of anxiety or obsessive-compulsive behavior.
Physical examination focuses on the anal region, particularly looking for perianal skin changes, signs of fecal staining or soilage (suggesting inadequate hygiene), and hemorrhoids. External inspection should also note the integrity of the perianal skin, whether it appears dull or thickened (suggesting chronicity), and the presence of any cutaneous lesions, fistulas, excoriations, or signs of local infection. Sphincter tone is assessed by having the patient contract the sphincter during digital rectal examination. The patient should then be asked to bear down as if for a bowel movement, which may show prolapsing internal hemorrhoids. Anoscopy may be necessary to further evaluate the anorectum for hemorrhoids.
Dermatologic examination may reveal scabies burrows in the inter-digital webbing or scalp or signs of any other contributing systemic skin disease.
The following findings are of particular concern:
Interpretation of findings:
Hygiene issues, use of topical agents, and local disorders (eg, candidal infection, hemorrhoids—see Hemorrhoids) are usually apparent by history and examination.
In adults with acute itching without obvious cause, ingested substances should be considered; a trial of eliminating these substances from the diet may be useful. In children, pinworms should be suspected.
In adults with chronic itching and no apparent cause, overly aggressive anal hygiene may be involved.
For many patients, a trial of empiric, nonspecific therapy is appropriate unless particular findings are noted. For example, biopsy, culture, or both of visible lesions of uncertain etiology should be considered. If pinworms, which occur most often in school-aged children, are suspected, eggs can be detected by patting the perianal skinfolds with a strip of cellophane tape in the early morning; the tape is placed side down on a glass slide and viewed microscopically.
Systemic causes and parasitic or fungal infections must be treated specifically.
Foods and topical agents suspected of causing pruritus ani should be eliminated.
Clothing should be kept loose, and bed clothing should be light. After bowel movements, the patient should clean the anal area with absorbent cotton or plain soft tissue moistened with water or a commercial perianal cleansing preparation for hemorrhoids; soaps and premoistened wipes should be avoided. Liberal, frequent dusting with nonmedicated talcum powder or cornstarch helps combat moisture. Hydrocortisone acetate 1% ointment, applied qid for a brief period (< 1 wk), may relieve symptoms. Sometimes, higher potency topical corticosteroids may be needed.
Last full review/revision July 2014 by Parswa Ansari, MD
Content last modified July 2014