Anal Itching: A Merck Manual of Patient Symptoms podcast

The perianal skin tends to itch, which can result from numerous causes (see Table 1: Anorectal Disorders: 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 Anorectal Disorders: 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.

Table 1
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Some Causes of Pruritus Ani Cause Suggestive Findings Diagnostic Approach Anorectal disorders Inflammatory bowel disease (eg, Crohn's 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 Nematodes (Roundworms): 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's disease, extramammary Paget's 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 Some Causes of Pruritus Ani Cause Suggestive Findings Diagnostic Approach Anorectal disorders Inflammatory bowel disease (eg, Crohn's 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 Nematodes (Roundworms): 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's disease, extramammary Paget's 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 Anorectal Disorders: 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) 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 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. HydrocortisoneSome Trade Names
CORTEF
SOLU-CORTEF
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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.

Last full review/revision July 2012 by Parswa Ansari, MD

Content last modified November 2012