Description

• Intense and often unpleasant anal and perianal itching
• Usually acute
• Common complaint seen by many physicians in primary care, dermatology, gastroenterology, and colorectal surgery
• Must be differentiated from other primary dermatologic disorders

Epidemiology

• The incidence ranges from 1–5% of the general population
• Predominant age: 40–70
• Predominant sex: Male > Female (4:1)

Prevalence
Difficult to estimate the prevalence as many cases are likely unreported, or actually related to hemorrhoids

Risk Factors

• Overweight
• Excess perianal hair growth, excessive perspiration
• Underlying anorectal pathology
• Underlying anxiety disorder

General Prevention

• Practice good perianal hygiene:
  • Absorb excess sweat with talcum powder or cornstarch.
• Avoid mechanical irritation of skin (vigorous cleaning or rubbing, harsh soaps or perfumed products, excessive cleansing with dry toilet paper or “baby wipes,” scratching with fingernails, or tight or synthetic undergarments).
• May wear cotton gloves at night if difficulty with nocturnal scratching
• Minimize moisture in perianal area (absorbent cotton in anal cleft may help keep area dry).
• Avoid laxative use (loose stool is an irritant).
• Eat yogurt or take Acidophilus supplements when taking broad-spectrum antibiotics:
  • Malt extract also may help.

Pathophysiology

• Perianal itching usually due to irritant in stool:
  • Excess alkalinity with antibiotics, tomatoes, wine, caffeine, intermittent stool seepage
• Itch–scratch cycle may be initiated via other mechanical or inflammatory factors and perpetuated by the resulting lichenification caused by scratching.

Etiology

• 50–90% idiopathic vs. 10–50% associated with colonic or anorectal pathology:
  • Hemorrhoids, anal fissures, skin tags, rectal prolapse, polyps, or—rarely—cancers of the colon, rectum, or anus
• In 50–75% of cases, the associated skin irritation is from feces:
  • Poor hygiene
  • Loose or leaking stool pathology that makes cleansing difficult
  • Laxity of the internal sphincter mechanism
• In the remaining cases, the inciting irritation may be caused by:
  • Dermatologic disorders:
    • Allergic contact dermatitis (e.g., to soaps, perfumes or dyes in toilet paper, topical anesthetics, oral antibiotics)
    • Excess skin moisture due to hyperhidrosis
    • Psoriasis: Lesions tend to be poorly demarcated, pale, and non-scaling.
    • Erythrasma (Corynebacterium infection)
    • Atopic dermatitis ± lichen simplex chronicus: Patients likely to have asthma and/or eczema
    • Eczema can result from dietary components (citrus, vitamin C supplements, milk products, coffee, tea, cola, chocolate, beer, wine).
    • Seborrheic dermatitis
    • Lichen planus: May be seen in patients with ulcerative colitis and myasthenia gravis
    • Local malignancy: Uncommon, but may be presenting symptom of Bowen or Paget disease.
  • Colorectal and anal: Rectal prolapse, internal hemorrhoids, anal fissures, anal fistulas, chronic diarrhea/constipation, papillomas, polyps, and cancer
  • Infection with dermatophytes (Tinea), bacteria (Staphylococcus aureus, β-hemolytic Streptococcus), virus (HSV, HPV), parasites (pinworms, rarely scabies, or pediculosis)
  • Mechanical factors: Vigorous cleaning and rubbing, tight-fitting clothes, or synthetic undergarments
  • Systemic disease: Diabetes mellitus (most common), chronic liver disease, renal failure, leukemia or lymphoma, hyperthyroidism, or anemia
  • Chemical irritation from chemotherapy or alkaline diarrhea
  • Psychogenic: Anxiety–itch–anxiety cycle

Commonly Associated Conditions

See above listing of conditions causing perianal irritation.