Anal Pruritus

Anal pruritus is chronic itching of the perianal skin (pruritus ani), often worse at night, which provokes scratching and a cycle of itch, skin damage and further itch. It affects 1 to 5% of the population, with men affected 4 times more than women, and a peak age of 40 to 60 years.

• Primary (idiopathic) pruritus ani accounts for about 50 to 90% of cases, when no cause is found after assessment. Secondary pruritus has an identifiable cause.
• Secondary causes:
  • Faecal soiling and seepage from loose stools, incomplete evacuation, anal leakage, haemorrhoids, skin tags, fissures, fistulae, prolapse and a flat or deep natal cleft.
  • Dermatological: irritant and allergic contact dermatitis (soap, wipes, perfumes, topical anaesthetics, neomycin), atopic dermatitis, seborrhoeic dermatitis, psoriasis (inverse), lichen simplex chronicus, lichen sclerosus, and lichen planus.
  • Infections: Candida, dermatophytes, erythrasma (Corynebacterium), perianal streptococcal dermatitis (especially in children), threadworm (Enterobius vermicularis), scabies, pediculosis, anal warts, herpes simplex, and sexually transmitted infections.
  • Systemic: diabetes mellitus, iron deficiency, liver disease, chronic kidney disease, thyroid disease, lymphoma and other malignancy, and HIV.
  • Neoplasia: Bowen disease, extramammary Paget disease, anal intraepithelial neoplasia, and anal squamous carcinoma.
  • Irritants and diet: excessive washing, soap, moist wipes, perfumed products, tight synthetic clothing, sweating, spicy foods, caffeine (coffee, tea, cola), tomatoes, citrus fruit, beer, chocolate, nuts, and milk products in some patients.
  • Medicines: colchicine, quinidine, mineral oil, antibiotics (diarrhoea, candidiasis), and laxatives.
  • Psychological: anxiety, stress, obsessive scratching, and neuropathic itch (sacral nerve root irritation).
• Mechanism in primary pruritus ani: low grade faecal contamination (especially from a high pressure or poorly closing anal canal, with internal sphincter dysfunction), moisture, and mechanical trauma from over cleaning, which damage the skin barrier, followed by an itch scratch cycle.

• Intense itching around the anus, most severe in the evening and at night, after a bowel movement, with sweating, and in warm conditions. It may extend to the perineum, scrotum or vulva. Burning, soreness and a sense of moisture may accompany it.
• Examination (with the patient in the left lateral position, with good lighting, with a chaperone and consent):
  • Early: erythema or a pale, thickened, white, macerated skin, with excoriations.
  • Chronic: lichenification (thickened, leathery skin with accentuated markings), fissuring, radial linear cracks, and pigment changes, or skin tags.
  • Secondary infection: weeping, crusting, pustules.
  • Specific signs: fiery red, sharply demarcated, moist rash (Candida or streptococcal), a well demarcated scaly plaque (psoriasis, tinea), a white atrophic figure-of-eight pattern (lichen sclerosus), perianal fissures, haemorrhoids and prolapse, warts, and an eczematous or ulcerated plaque that does not heal (Paget disease, Bowen disease, cancer).
• Differential diagnosis: all causes listed, including anal fissure, abscess or fistula, proctitis, inflammatory bowel disease, and a pilonidal condition.
• Red flags: a visible lump, a non-healing ulcer or plaque, bleeding, weight loss, a change in bowel habit, pain, persistent symptoms beyond 6 weeks of treatment, lymph node enlargement, a history of anal intraepithelial neoplasia or HIV, and age over 50 years with new symptoms.
• Complications: sleep loss, skin breakdown, secondary infection, contact sensitisation from topical agents, steroid atrophy from excess use, psychological distress, and sexual dysfunction.

• Careful history: duration, timing, hygiene practices, products used (soap, wipes, creams), diet, bowel habit and soiling, anal symptoms (bleeding, pain, prolapse), skin disease, medicines, diabetes, sexual history, contacts with itching (threadworm and scabies), and previous treatments.
• Examination: perianal skin, the anal verge, digital rectal examination, and proctoscopy (anoscopy) to look for haemorrhoids, fissures, fistulae, rectal prolapse, and masses. Examine the rest of the skin and the genitalia, and check for scabies, psoriasis, lichen sclerosus, and tinea.
• Tests as indicated:
  • Skin scraping for fungus (potassium hydroxide preparation) and swab for bacterial and Candida culture when weeping or infected.
  • Adhesive tape test for threadworm ova or inspection for worms at night (obtain 3 morning samples).
  • Fasting glucose or HbA1c, full blood count, ferritin, liver and renal function, and thyroid function tests.
  • Patch testing for suspected contact allergy when the cause is unclear or the itch persists.
  • Stool tests (culture, parasites, calprotectin) when diarrhoea or soiling is present.
  • Sexually transmitted infection testing when risk factors exist.
  • Biopsy of any non-healing, pigmented or ulcerated area, or an atypical plaque (for Bowen disease, Paget disease, or cancer), and when the diagnosis remains in doubt after 6 weeks of treatment.
  • Colonoscopy or flexible sigmoidoscopy for a change in bowel habit, bleeding, anaemia, or age over 50 years with persistent symptoms.
  • Anorectal physiology in selected patients with soiling.

• Explain that the condition is common and treatable, that scratching and over washing worsen it, and that treatment may take 2 to 4 weeks.
• Hygiene and skin care (the foundation):
  • Stop all soaps, wipes, perfumed products, powders, and over-the-counter creams. Clean the area gently after a bowel movement with plain lukewarm water (a shower, bidet, or a hand held jug), and pat dry with soft tissue or a hairdryer on a cool setting. Do not rub or scrub.
  • Apply a barrier cream (zinc oxide paste or dimethicone) after cleaning and at night, to protect the skin from moisture and stool.
  • Wear loose cotton underwear, change after sweating, and avoid tight synthetic clothing. Place a small piece of cotton wool or soft gauze at the anal verge to absorb moisture in soiling, and change it regularly.
  • Keep nails short, and wear cotton gloves at night to reduce scratching damage. Do not use dry toilet tissue repeatedly.
• Dietary changes: reduce coffee, tea, cola, chocolate, beer, spicy foods, tomatoes, citrus, and milk products for 2 to 4 weeks, then reintroduce individually. Add fibre (ispaghula husk 3.5 g once to twice daily, with 200 mL water) to bulk the stool and reduce seepage, and use loperamide 2 mg after loose stools when diarrhoea contributes.
• Topical corticosteroid for inflamed, itchy skin: hydrocortisone 1% cream or ointment applied thinly 1 to 2 times daily for 2 weeks, then once daily for 1 week, then stop (a maximum of 4 weeks). Avoid potent steroids (risk of skin atrophy, thinning and striae), except for lichen sclerosus. For severe or chronic eczema, mometasone furoate 0.1% ointment once daily for up to 1 to 2 weeks may be used under supervision, followed by tapering.
• Candida and other fungal infection: clotrimazole 1% cream, or miconazole 2% cream, applied 2 to 3 times daily for 2 to 4 weeks, with a hydrocortisone 1% and clotrimazole 1% combination when inflamed (up to 2 weeks). Fluconazole 150 mg orally once weekly for 2 to 3 doses for resistant or extensive infection.
• Bacterial infection: mupirocin 2% ointment 3 times daily for 7 days, or fusidic acid 2% cream 3 times daily for 7 days, for localised infection. Perianal streptococcal dermatitis: phenoxymethylpenicillin 500 mg orally 6 hourly for 10 days (child 12.5 mg/kg 6 hourly), or amoxicillin 500 mg 8 hourly for 10 days. Erythrasma: clarithromycin 500 mg 12 hourly for 14 days, or topical clindamycin 1% twice daily for 2 weeks.
• Threadworm: mebendazole 100 mg orally as a single dose, repeated after 2 weeks (age over 6 months), or albendazole 400 mg once, repeated after 2 weeks, for the patient and all household contacts, with hygiene measures (washing hands, trimming nails, washing bedding and underwear at 60 C, and morning showers) for 6 weeks. Avoid in the first trimester of pregnancy, so use hygiene measures alone.
• Scabies: permethrin 5% cream applied to the whole body from the neck down, left for 8 to 12 hours and washed off, repeated after 7 days, with treatment of all household contacts at the same time.
• Lichen sclerosus: clobetasol propionate 0.05% ointment once daily for 4 weeks, then on alternate days for 4 weeks, then twice weekly for 4 weeks, with specialist review and long term follow up because of a risk of squamous carcinoma (about 3 to 5%).
• Psoriasis: hydrocortisone 1% ointment for up to 2 weeks (calcipotriol 0.005% ointment with caution on thin skin), with dermatology review.
• Contact dermatitis: identify and stop the allergen or irritant, and use emollient and a mild steroid.
• Refractory primary pruritus ani (after 4 to 6 weeks of hygiene and a short course of steroid):
  • Capsaicin 0.006% cream applied 4 times daily for 4 weeks, which gives relief in about 70% (burning is the main adverse effect, which usually settles within the first week).
  • Tacrolimus 0.1% ointment applied twice daily for 4 to 6 weeks, in specialist care, as a steroid sparing treatment (burning on application is common).
  • Oral antihistamine at night for sleep and scratching: hydroxyzine 10 to 25 mg orally at night, or chlorphenamine 4 mg at night (avoid in the elderly, glaucoma, prostatic enlargement). Non-sedating antihistamines are of little benefit.
  • Neuromodulators for neuropathic or chronic itch: amitriptyline 10 mg orally at night, increased by 10 mg weekly to 25 to 50 mg, or gabapentin 100 mg at night, titrated to 300 mg 3 times daily, or sertraline 25 to 50 mg daily, when anxiety is prominent.
  • Intradermal methylene blue injection (a total of 10 to 30 mL of a 0.25 to 1% solution into the perianal skin, under local anaesthetic) in specialist care, which gives relief in 60 to 90% for months, with a risk of skin ulceration and necrosis.
  • Botulinum toxin injection for refractory cases, and treatment of internal sphincter dysfunction in selected patients.
• Treat underlying anorectal disease: haemorrhoids (fibre, topical therapy, banding), fissures (glyceryl trinitrate 0.4% ointment 2 to 3 times daily for 6 to 8 weeks, or diltiazem 2% ointment twice daily), fistula (surgery), skin tags (removal only if hygiene is impaired), and prolapse (surgical review). Treat diabetes, iron deficiency, and other systemic causes.
• Surgery and tumour treatment: excision for Paget disease and Bowen disease, and oncological care for cancer.
• Special groups:
  • Children: the commonest causes are threadworm, perianal streptococcal dermatitis, constipation with soiling, and eczema. Treat the cause, apply zinc oxide, and use hydrocortisone 1% for up to 1 week. Examine for sexual abuse when the findings or history are concerning.
  • Pregnancy: use hygiene measures, barrier cream, and hydrocortisone 1% for short periods. Treat haemorrhoids and constipation, and avoid mebendazole in the first trimester.
  • Elderly: consider faecal incontinence, dementia, skin atrophy, malignancy, and systemic causes. Use barrier creams and avoid prolonged steroid use.
  • Diabetes: optimise glucose control, treat Candida, and examine for urinary leakage.
  • Immunosuppressed and HIV: screen for anal intraepithelial neoplasia, herpes, warts, and opportunistic infection.
• Follow up: review at 2 to 4 weeks. Review the diagnosis if there is no improvement at 6 weeks, and refer to a colorectal surgeon or dermatologist for refractory symptoms, suspected neoplasia, or the need for biopsy or injection therapy. Advise long term hygiene measures to prevent relapse, which occurs in about 30 to 50%.