Chapter 25 — Pruritus Ani
Pruritus ani means itching around the anus. It is one of the most common anorectal complaints. It is often chronic, and can significantly affect quality of life. This chapter explains pruritus ani in full. It covers presentation, examination, differential diagnosis, investigations, and management. This is the same pattern used for every disease chapter in this manual.
25.1 What Is Pruritus Ani
Pruritus ani is persistent itching of the skin around the anus. It is a symptom, not a single disease.
Most cases have no identifiable cause. This is called primary, or idiopathic, pruritus ani. A smaller number of cases have a specific, identifiable underlying cause. This is called secondary pruritus ani.
Distinguishing primary from secondary pruritus ani matters greatly. Secondary cases need the underlying condition treated directly. Primary cases need a different approach, described in Section 25.8.
25.2 Why It Happens
Several anorectal conditions can cause soiling or leakage, which irritates the skin and causes itching. These include haemorrhoids, described in Chapter 10, fissure-in-ano, described in Chapter 11, fistula-in-ano, described in Chapter 12, skin tags, and rectal prolapse, described in Chapter 14.
Several skin conditions can affect this area directly. These include psoriasis, eczema, contact dermatitis from soaps or wipes, and lichen sclerosus.
Infections are a common cause. Fungal infection, particularly candida, is common, especially in a patient with diabetes. Threadworm infection is a common cause in children. Some sexually transmitted infections, described in Chapter 24, can also cause itching.
Systemic conditions can cause pruritus ani as part of a wider pattern. These include diabetes mellitus and liver disease.
Diet can also play a role. Caffeine, alcohol, spicy food, and citrus fruit all worsen symptoms in some patients.
Hygiene habits matter in both directions. Poor hygiene allows irritant residue to remain on the skin. Excessive hygiene, particularly vigorous wiping or scrubbing, damages the skin barrier and makes itching worse, not better.
25.3 The Itch-Scratch Cycle
Scratching gives temporary relief, but damages the skin further. Damaged skin itches more. This creates a self-perpetuating cycle, known as the itch-scratch cycle.
Chronic scratching causes visible changes to the skin. These include excoriation, which is surface damage from scratching, and lichenification, which is thickening and hardening of the skin from long-standing irritation.
Breaking this cycle is central to successful treatment, regardless of the underlying cause. Section 25.8 covers this in full.
25.4 Presentation
Follow the history-taking method described in Chapter 2.
Itching is the main symptom. It may be constant, or it may come and go. It is often worse at night, and often worse after a bowel movement.
Burning or soreness may accompany the itching, particularly once the skin is excoriated.
Ask specifically about hygiene habits, including how the patient cleans the area, and how often.
Ask about diet, including caffeine, alcohol, and spicy food intake.
Ask about associated symptoms. Bleeding, discharge, or a feeling of prolapse suggest a secondary cause, and should prompt a careful search for an underlying anorectal condition.
Ask about diabetes, liver disease, and any new soaps, wipes, or medications applied to the area.
25.5 Examination
Follow the sequence described in Chapter 3.
Inspection, described in Chapter 4, is the most important step. Look for excoriation and lichenification, described in Section 25.3. Look for skin changes suggesting a specific dermatological condition. Look for evidence of moisture, soiling, or discharge. Look specifically for haemorrhoids, a fissure, skin tags, or a prolapse, since any of these can be the underlying cause.
Digital rectal examination, described in Chapter 5, checks for other anorectal pathology.
Proctoscopy, described in Chapter 6, is useful if an underlying anorectal condition is suspected but not clearly seen on inspection alone.
25.6 Differential Diagnosis
Primary, idiopathic pruritus ani — a diagnosis reached only after secondary causes have been carefully excluded, not simply assumed by default.
Anorectal conditions causing soiling — haemorrhoids, fissure, fistula, skin tags, and rectal prolapse, described in Chapters 10, 11, 12, and 14.
Dermatological conditions — psoriasis, eczema, contact dermatitis, and lichen sclerosus. A dermatology referral is appropriate if one of these is suspected but not clearly confirmed.
Fungal or parasitic infection — described further in Section 25.7.
Sexually transmitted conditions, described in Chapter 24.
25.7 Investigations
Pruritus ani is usually a clinical diagnosis, made on history and examination.
A skin scraping or swab can confirm a suspected fungal infection.
A sellotape test, applied to the perianal skin first thing in the morning and examined under a microscope, can confirm threadworm infection, particularly in a child.
Blood glucose testing is reasonable if diabetes is suspected but not already diagnosed.
A skin biopsy is reserved for a persistent, unexplained case, or a case that does not respond to appropriate treatment, to exclude a specific dermatological condition requiring different management.
25.8 Principles of Management
Identify and treat any secondary cause directly. This is the single most important step, and should always be attempted before treating the itching as idiopathic.
General hygiene advice helps every patient, regardless of the underlying cause. Clean the area gently, using water alone or a mild, unperfumed cleanser. Pat the area dry, rather than rubbing it. Avoid vigorous wiping.
Avoid known dietary triggers, if the patient has identified any, such as caffeine, alcohol, spicy food, or citrus fruit.
Break the itch-scratch cycle described in Section 25.3. Keep fingernails short. Consider wearing soft cotton gloves at night, to reduce the damage caused by scratching during sleep.
A barrier cream, such as zinc oxide, protects the skin from further irritation.
A short course of a mild topical steroid can help settle significant inflammation. Use this only for a short, defined period. Prolonged use thins the skin, and can make the underlying problem worse over time.
Treat any specific cause found directly. This includes an antifungal treatment for a fungal infection, an antiparasitic treatment for threadworm, or definitive treatment of an underlying anorectal condition such as haemorrhoids or a fistula.
25.9 Special Situations
A child with pruritus ani — consider threadworm infection first, and examine or treat accordingly.
A patient with diabetes — consider fungal infection, and check that blood glucose control is adequate, since poor control makes fungal infection more likely and harder to clear.
A recalcitrant case, not responding to the measures above — reconsider the diagnosis carefully. A dermatology referral, or a skin biopsy, described in Section 25.7, may be needed at this stage.
25.10 Complications
Skin breakdown, and secondary bacterial infection, from ongoing scratching.
Lichenification, described in Section 25.3, from long-standing irritation.
Significant psychological distress, given the constant, often embarrassing nature of the symptom, and its impact on sleep and daily comfort.
25.11 Common Mistakes to Avoid
Assuming every case is idiopathic, without a careful search for a secondary cause.
Using a topical steroid for a prolonged period, causing skin thinning rather than lasting improvement.
Not addressing the itch-scratch cycle directly, and treating only the underlying cause.
Missing an underlying anorectal condition, such as haemorrhoids or a fistula, that is causing soiling and secondary irritation.
Not asking about hygiene habits, since both insufficient and excessive hygiene can be the true underlying problem.
25.12 Recording and Follow-Up
Record the suspected cause, the examination findings, and the treatment plan. For example: "Pruritus ani, likely secondary to grade 2 haemorrhoids with mucus leakage. Plan: haemorrhoid management, hygiene advice given, barrier cream. Review in 4 weeks." Arrange follow-up to confirm the itching has settled, and to reconsider the diagnosis if it has not.
25.13 Why This Chapter Matters
Pruritus ani is common, often distressing, and often treated as a single, simple problem when it is not. A careful search for a secondary cause, combined with breaking the itch-scratch cycle, resolves the great majority of cases. The next chapter turns to a more serious condition that must always be considered in this region: anorectal malignancy.