Itchy anus

Itchy anus is a common complaint characterized by intense itching in the perianal area between the buttocks. It can result from infestations, skin infections, inflammatory skin conditions, or rarely, skin tumors. When there is no obvious cause, it is referred to as pruritus ani.

Demographics

Itchy anus affects up to 5% of individuals at some point in their lives. Men are more commonly affected than women, with a male-to-female ratio of 4:1. It is most commonly seen in individuals in their fourth to sixth decades of life.

Causes

Itchy anus can be classified as primary (idiopathic) or secondary.

• Primary Pruritus Ani: More common than secondary and includes factors like
  • perianal hypertrichosis
  • perianal hyperhidrosis
  • deeply set anal opening
  • irritating stools (diarrhea or consumption of acidic/spicy foods)
  • overzealous cleaning, and use of personal care products
  • systemic diseases (e.g., diabetes mellitus, liver disease).
• Secondary Perianal Itch: Results from common skin diseases involving the anogenital area, including :
  • bacterial infections (perianal streptococcal dermatitis)
  • fungal infections (candidal intertrigo), viral infections (anogenital warts)
  • infestations (pinworms)
  • inflammatory skin conditions (atopic dermatitis, seborrheic dermatitis, flexural psoriasis, lichen sclerosus, lichen planus)
  • skin tumors (anal squamous cell carcinoma, extramammary Paget disease).

Clinical Features

Itchy anus is a symptom requiring a detailed history and skin examination to diagnose. Important aspects include the onset and duration of symptoms, bowel habits, cleaning routine, medication history, and the time of day when itching occurs. Physical examination should assess the anogenital skin and the entire skin surface.

Complications

• Lichen simplex
• Contact dermatitis due to treatments
• Secondary skin infections

Diagnosis

Pruritus ani is diagnosed based on a normal examination of the perianal skin, aside from possible secondary excoriations and lichenification. Secondary itchy anus is diagnosed through history and examination, with investigations such as:

• Skin swab for bacteriology
• Skin scraping for mycology
• ‘Sticky tape’ test for pinworm ova
• Patch testing for allergic contact dermatitis
• Skin biopsy for inflammatory disorders or skin cancer

Differential Diagnoses

• Psychogenic pruritus
• Compulsive skin picking

Treatment

General Measures:

• Cleanse gently with plain water, using a bidet or showerhead after defecation.
• Avoid abrasive/fragranced toilet tissue; use cotton wool dipped in water or unscented wet wipes.
• Pat the skin dry, avoid talc, use cool compresses, avoid scratching, and keep fingernails short.
• Wear loose cotton underwear, avoid soaps and detergents, and use light emollients like aqueous cream.
• Increase dietary fiber and avoid exacerbating foods (spicy foods, tea, coffee, alcohol, etc.).

Specific Measures:

• Treat the underlying condition.
• Avoid contact with potential topical allergens.

Topical Treatments for Itch:

• Bland emollient or barrier cream (e.g., white soft paraffin or zinc oxide cream)
• Short-term low-potency topical steroid
• Local anesthetic spray or ointment (e.g., lignocaine)

Systemic and Other Treatments for Itch:

• Sedating antihistamines at night
• Tricyclic antidepressants
• Local methylene blue intradermal injections (anal tattooing)