Pruritus Ani

Condition

Itching of the perianal skin. Persistent scratching usually causes lichenification; symptoms are often exacerbated by stress. Associated with dermatitis, psoriasis, and lichen planus. Not caused by lack of hygiene, incontinence, or poor wiping technique, though these can make the problem worse.

Consider when diagnosing: skin conditions elsewhere on the body; irritant dermatitis (sweat, faecal incontinence, allergens, overzealous cleaning); other anal pathology (fissures, skin tags, haemorrhoids); Crohn’s disease; in children — threadworm, streptococcal perianal dermatitis.

Demographics: adult males; children (threadworm).

History and examination

Perianal itching, often worse at night, in hot weather, and during exercise; may be worse with stress. Examination shows perianal irritation and excoriation, with lichenification if long-standing.

Investigations

Rule out infection if the skin is weeping, ulcerated, or blistered. Stool examination for suspected parasites.

Management

Treat the underlying cause if known; break the itch-scratch cycle.

General measures: clean gently with moistened cotton wool; soap substitute; emollients; promote bulkier stool with a bulk-forming laxative.

If no underlying cause is found and conservative measures fail, trial a topical steroid: methylprednisolone aceponate 0.1% (Advantan) fatty ointment daily for up to 4 weeks (if lichenified, use betamethasone valerate 0.05% daily for up to 4 weeks first, followed by the above to prevent recurrence).

Once resolved, continue general measures — this is a chronic condition requiring ongoing treatment; use a steroid again at the first sign of itch. Refer for expert (dermatology) advice if not responding.