# Pruritus Ani > Pruritus ani in FMGE Surgery: idiopathic and secondary causes, pinworm diagnosis, dietary triggers, hygiene rules and when to biopsy a plaque. - Canonical URL: https://prepelephant.com/topics/fmge/surgery/pruritus-ani - Exam / course: FMGE · Subject: Surgery - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Pruritus Ani", PrepElephant, https://prepelephant.com/topics/fmge/surgery/pruritus-ani ## Direct answer Nocturnal perianal itching in a child means pinworms until excluded, and in adults the same symptom runs a long differential that most often ends as idiopathic pruritus ani — a diagnosis made only after excluding every secondary cause. The systematic list covers parasitic (Enterobius vermicularis, confirmed by a cellophane tape test in the early morning), fungal (Candida, especially in diabetics), dermatological (psoriasis, lichen sclerosus, contact dermatitis from over-washing and medicated wipes), anorectal conditions with soilage (haemorrhoids, fissure, fistula, mucosal prolapse, poor sphincter function), dietary irritants (coffee, tea, cola, chocolate, citrus, tomatoes, beer and spicy food) and systemic disease (diabetes mellitus, jaundice, uraemia). Management is anti-itch discipline before drugs: gentle water cleansing without soap, thorough drying, loose cotton underwear, short fingernails, a two-week exclusion diet for suspected triggers, and treatment of the specific cause found — with biopsy of any thickened, unilateral or non-healing plaque to exclude anal Bowen's disease or squamous carcinoma. ## What you must remember - **Frequency hierarchy:** idiopathic pruritus ani is the single largest group once secondary causes are excluded; among identifiable causes, anorectal soilage conditions and dermatitis dominate. - **Parasitic classic:** Enterobius vermicularis — nocturnal perianal itch from egg-laying female worms, tape test in the morning is diagnostic, treated with albendazole or mebendazole (treat the household). - **Fungal and infective:** Candida intertrigo in diabetics and after antibiotic use; bacterial infection; sexually transmitted causes including condylomata in at-risk adults; scabies when itching is nocturnal and familial. - **Dermatological:** psoriasis (silvery scale, extensor surfaces), lichen sclerosus (atrophic white plaques), contact dermatitis from soaps, wipes and topical anaesthetics — the "itch-scratch cycle" sustains all of them. - **Anorectal sources:** internal haemorrhoids, mucosal prolapse, fissure, fistula and incontinence cause subclinical soiling whose moisture and irritant leakage drives the itch; treat the source. - **Dietary triggers worth quoting:** coffee, strong tea, cola, chocolate, citrus fruits, tomatoes, beer and heavily spiced food — withdraw for two weeks and reintroduce one at a time. - **Systemic screen:** random glucose (diabetes), liver function (jaundice, cholestasis), renal function (uraemia), and thyroid status where indicated. - **Red-flag rule:** a unilateral, thickened, fixed, ulcerated or bleeding lesion is biopsy territory — anal Bowen's disease, Paget's disease or squamous cell carcinoma present as "intractable itching". ## How to work through a resistant case A 48-year-old man has scratched his perianal skin for two years, has seen three practitioners and used assorted creams that helped briefly and then flared. The consult restarts from zero: examination shows excoriated, macerated skin but also second-degree internal haemorrhoids that prolapse on straining — a plausible soiling source. Step one is hygiene correction: stop all creams including the steroid he has been using (topical steroid overuse thins perianal skin and perpetuates itching), wash with plain water after each stool, pat dry, cotton underwear. Step two is a two-week exclusion of coffee and beer, his heavy staples. Step three is definitive treatment of the haemorrhoids by banding, closing the soiling tap. A short course of a mild topical steroid for no more than a week or two settles the inflamed skin meanwhile. In the child version of this consult, the same discipline applies in reverse order: tape test first, albendazole for the whole family, nails cut, pyjamas and bed linen washed — and the night-time itch vanishes. ## How the exam frames it Question writers attach the itch to its cause and expect pattern-matching: child with nocturnal itch — pinworms and tape test; diabetic with satellite lesions — Candida; any adult with a unilateral thickened plaque — biopsy for malignancy before another word of treatment. The pharmacology crossover is emollients and mild steroids versus prolonged potent-steroid harm, and the parasitology crossover is the household-treatment rule for Enterobius. ## Frequently asked questions ### Which parasite classically causes nocturnal perianal itching? Enterobius vermicularis (pinworm); female worms migrate to the perianal skin at night to lay eggs, detected by a morning cellophane tape test. ### What is the first-line management of idiopathic pruritus ani? Perianal hygiene discipline — water cleansing without soap, thorough drying, cotton underwear, breaking the itch-scratch cycle — followed by elimination of dietary triggers. ### When is a skin biopsy mandatory in pruritus ani? For any unilateral, thickened, ulcerated, fixed or bleeding lesion, to exclude anal intraepithelial neoplasia, Bowen's disease, Paget's disease or squamous carcinoma. ### Which anorectal conditions drive pruritus through soiling? Internal haemorrhoids, mucosal prolapse, fissure, fistula and sphincter weakness, whose mucus and faecal leakage irritate perianal skin. ### Why should prolonged topical steroids be avoided? Potent steroids applied long-term thin and damage the perianal skin, deepening the itch-scratch cycle — they are limited to short courses under review.