What causes anal pruritis?

Causes of Anal Pruritus

Anal pruritus is primarily caused by anorectal diseases, infections, dermatological conditions, and systemic diseases that require targeted evaluation and treatment based on the underlying etiology. 1

Common Etiologies

Anorectal Causes

• Anorectal diseases: Hemorrhoids, anal fissures, anal spasm, and occult mucosal prolapse 2
• Perianal abscesses: Originating from obstructed anal crypt glands 3
• Fecal soiling: Due to poorly formed stools or incomplete evacuation (affects 48-50% of patients) 4

Infectious Causes

• Fungal infections:
  • Candida species
  • Dermatophytes 2
• Parasitic infections:
  • Enterobius vermicularis (pinworm/threadworm): Causes intense perianal itching, especially at night 3
  • Hookworm (Ancylostoma duodenale/Necator americanus): Can cause "ground itch" 3
  • Strongyloides stercoralis 3
  • Tapeworms (Taenia species) 3
• Sexually transmitted infections 1

Dermatological Conditions

• Psoriasis 4
• Erythrasma 4
• Contact dermatitis: From soaps, detergents, or topical medications 5

Systemic Diseases

• HIV infection: Pruritus typically occurs at late stages but can be a presenting feature 3
  • Correlates directly with viral load
  • Often associated with eosinophilia
  • Can be related to xerosis, drug therapies, photosensitivity, or specific dermatoses like eosinophilic folliculitis 3
• Hepatitis (A, B, C, E): Causing cholestatic pruritus 3
• Diabetes mellitus 6

Drug-Induced Causes

• Medications: Many drugs can cause pruritus with or without rash 3
  • Opioids: Affect 2-10% of patients receiving oral, 10-50% intravenous, and 20-100% epidural/intrathecal administration 3
  • Epidural dexamethasone 3

Other Factors

• Dietary factors: Certain foods may trigger pruritus in susceptible individuals 4
• Excessive hygiene: Overzealous cleaning and application of multiple medications can worsen symptoms 4
• Psychological factors: Stress and anxiety can exacerbate symptoms 3

Diagnostic Approach

1. Visual examination: Assess for abnormalities using classifications like the Washington classification 1
2. Digital anorectal examination: Essential for detecting anorectal diseases 1
3. Anoscopy: To exclude anorectal diseases or suspicious masses 1
4. Laboratory investigations:
   • Complete blood count (to check for eosinophilia)
   • Stool examination for ova and parasites
   • Skin scrapings for fungi
   • Blood glucose levels
   • Liver function tests 6
5. "Sellotape test": For diagnosing pinworm infection by placing adhesive tape on perianal skin and examining for ova 3

Management Principles

Triple Approach Strategy

1. Proper hygiene: Clean the area gently without excessive rubbing 1, 4
2. Elimination of irritants: Identify and remove dietary triggers and irritating products 1, 4
3. Skin care and protection: Apply appropriate barrier creams 1

Treatment Based on Specific Causes

• Anorectal diseases: Treat the underlying condition first before considering antifungal therapy 2
• Parasitic infections:
  • Pinworm: Albendazole 400 mg or mebendazole 100 mg as a single dose 3
  • Hookworm: Albendazole 400 mg daily for 3 days 3
  • Threadworm: Albendazole 400 mg twice daily for 21 days with monitoring of liver function and blood count 3
• Fungal infections: Topical azole preparations if infection persists after treating underlying conditions 7, 2
• HIV-related pruritus: Consider indomethacin 25 mg three times daily or hypnosis 3

Topical Treatments

• Mild hydrocortisone cream: For idiopathic pruritus ani 4
• Other options: Capsaicin, tacrolimus, and methylene blue intradermal injections for refractory cases 1

Important Considerations

• Patients often delay seeking medical attention due to embarrassment 1
• Many patients are concerned about cancer as a cause and need reassurance 4
• Treatment has a good prospect of regression of symptoms and skin changes when the underlying cause is addressed 5
• Avoid overzealous cleaning and application of multiple medications as these can worsen symptoms 4

Remember that treating the underlying anorectal condition often resolves the pruritus without the need for specific antifungal or antipruritic treatments 2.