Typical Patient Profile:
- Typically an anxious and/or overweight male aged 40–60 years.
- Often has a colonic reflex associated with stress.
- Experiences persistent pruritus and constant urge to scratch, causing distress and embarrassment.
Aetiology
Idiopathic Causes:
- Up to a quarter of cases of anal pruritus are idiopathic.
Benign Aetiology:
- Majority of cases result from a combination of faecal soiling and dietary factors.
- Local anorectal disorders and contact dermatitis of the perianal skin may exacerbate the problem.
Faecal Soiling, Diet, and the Itch-Scratch Cycle
Causes of Faecal Soiling:
- Poor hygiene, anatomical abnormalities (e.g., haemorrhoids, fissures, skin tags), or internal anal sphincter dysfunction.
- Abnormal bowel motions, including diarrhoea (food intolerance, antibiotics, laxatives, enemas) and constipation (causing fissures).
Contributing Factors:
- Sweating associated with inappropriate clothing or obesity.
- These factors lead to irritation and subsequent scratching, damaging the perianal skin and worsening the itch-scratch cycle.
Anorectal Conditions
Common Conditions:
- Up to half of patients with pruritus ani have an anorectal disorder, most commonly haemorrhoids.
Serious Conditions:
- Anal cancers, perianal Paget disease, and perianal Bowen disease may present with itch.
Skin Disorders
Contact Dermatitis:
- Caused by a wide range of topical agents (soaps, shower gels, creams, talc, perfumed/bleached toilet paper, baby wipes, latex condoms).
- Patients often overwash with soap products or use over-the-counter products, worsening the problem.
Therapeutic Agents:
- Haemorrhoid preparations can cause contact dermatitis (e.g., benzocaine, a common allergen).
Infections
Fungal Infections:
- Account for up to 15% of cases of pruritus ani.
- Candida is more likely pathogenic in patients with diabetes, after steroid treatment, and after systemic antibiotic use.
Bacterial Infections:
- Include beta haemolytic streptococci and Staphylococcus aureus, causing chronic symptoms.
- Erythrasma, a cutaneous infection by Corynebacterium minutissimum, can be diagnosed by Wood’s light fluorescence.
Parasitic Infections:
- Threadworms, often infect multiple family members.
- Sexually transmissible infections (STIs) including genital warts, genital herpes, syphilis, gonorrhoea, Chlamydia trachomatis, molluscum contagiosum, and scabies.
Investigations
Initial Review:
- Comprehensive history and full physical/dermatological examination are crucial.
- Consider factors like resource limitations, cognitive impairment, depression, or physical disability in the elderly that may lead to neglect of hygiene.
Tests:
- Full blood count (infection, worm infestation, atopy).
- Immunoglobulin E.
- Blood glucose.
- Syphilis serology (if signs of possible syphilis infection).
- Tissue transglutaminase (coeliac screen).
- Swabs for microscopy and culture (fungal, streptococcal, staphylococcal, gonococcal, and Corynebacterium infections).
- Anal PCR swabs for STIs, PCR swabs from lesions for HSV, syphilis, and vaginal swabs.
- Patch tests if contact dermatitis is suspected.
- Nocturnal cellotape test and/or stool test for helminths.
Management
Normalisation of Bowel Motions:
- Additional fibre and adequate fluid intake to achieve well-formed stools.
Cleaning After Defaecation:
- Avoid overzealous cleaning.
- Use non-irritant cleaning methods (bidet, lukewarm water, wet cloth, or moist cotton wool).
Clothing:
- Wear loose, natural fibre clothing.
- Avoid prolonged sitting.
Soaps and Cleansers:
- Advise against using soap; use aqueous cream or soap-free cleanser.
- Cease the use of other creams or potential irritants.
Avoid Scratching:
- Trim fingernails and wear gloves or mittens to bed to prevent scratching during sleep.
Medications:
- Zinc cream.
- Mild hydrocortisone 1% ointment (contains fewer potential preservative irritants).