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Pruritus Ani (Anal Itching)

by Parswa Ansari, MD

The perianal skin tends to itch, which can result from numerous causes (see 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.

Etiology

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 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.

Some Causes of Pruritus Ani

Cause

Suggestive Findings

Diagnostic Approach

Anorectal disorders

Inflammatory bowel disease (eg, Crohn disease)

Purulent discharge

Pain in the rectum (sometimes) and/or abdomen (often)

Sometimes draining fistula

Sometimes diarrhea

Anoscopy, sigmoidoscopy, or colonoscopy

Hemorrhoids (internal or external)

With internal hemorrhoids, bleeding (a small amount of blood on toilet paper or in the toilet bowl)

With external hemorrhoids, a painful, swollen lump on the anus

Clinical evaluation

Usually anoscopy or sigmoidoscopy

Infections

Bacterial infection (secondary to scratching)

Inflamed, excoriated area

Clinical evaluation

Candida

A rash around the anus

Clinical evaluation

Sometimes examination of skin scrapings

Pinworms

Usually in children

Sometimes present in several family members

Microscopic examination of transparent tape that was applied to the anal area to check for pinworm eggs (see Diagnosis)

Scabies

Intense itching, usually worse at night

Possibly itching of other body areas

Possibly pink, thin, slightly raised lines or bumps (burrows) on the affected areas

Clinical evaluation

Examination of skin scrapings

Skin disorders

Atopic dermatitis

An itchy, red, oozing, and crusty rash

Clinical evaluation

Perianal carcinoma (eg, Bowen disease,extramammary Paget disease)

Scaly or crusted lesion

Biopsy

Psoriasis

Typical psoriatic plaques

Sometimes plaques on other areas of the skin

Clinical evaluation

Skin tags

Small flap of tissue on anus

Clinical evaluation

Drugs

Antibiotics

Current or recent antibiotic use

Trial of elimination

Foods and dietary supplements

Beer, caffeine, chocolate, hot peppers, milk products, nuts, tomato products, citrus fruits, spices, or vitamin C tablets

Symptoms only after ingestion of substance

Trial of elimination

Hygiene-related problems

Excessive sweating

Excessive sweating described by the person, particularly with wearing of tight and/or synthetic clothing

Trial of measures to limit sweating (eg, wearing loose cotton underwear, changing underwear frequently)

Overly meticulous or aggressive cleansing of the anal area

Poor cleansing

Inappropriate cleansing practices described by the patient

Trial of a change in cleansing practices

Skin irritants

Local anesthetics, ointments, soaps, and sanitary wipes

Use of a possibly irritating or sensitizing substance described by the patient

Trial of elimination

Evaluation

History

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: 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.

Physical examination

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.

Red flags

The following findings are of particular concern:

  • Draining fistula

  • Bloody diarrhea

  • Large external hemorrhoids

  • Prolapsing internal hemorrhoids

  • Perianal fecal soilage

  • Dull or thickened perianal skin

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.

Testing

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.

Treatment

Systemic causes and parasitic or fungal infections must be treated specifically.

Foods and topical agents suspected of causing pruritus ani should be eliminated.

General measures

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.

Key Points

  • Pinworms in children and hygiene-related issues in adults are common causes.

  • Foods and detergents or soaps can cause anal itching.

  • Practicing appropriate, nonirritating hygiene (ie, not too little but not too vigorous, avoiding strong soaps and chemicals) and decreasing local moisture can help alleviate symptoms.

Resources In This Article

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