01OverviewDefinition, clinical context and the essential points that orientate the chapter.
Perianal itching is a presentation with several possible mechanisms, often operating together. Small amounts of stool or mucus, moisture, friction and local products can impair the skin barrier. Scratching then produces excoriation and more inflammation, creating an itch–scratch cycle. Patients may respond by washing more frequently or adding multiple haemorrhoid creams, which can increase irritation or introduce a contact allergen. A nonjudgmental history should therefore ask exactly what touches the skin rather than assume inadequate cleanliness.
Bowel function and the surrounding anatomy matter. Loose stool, leakage, prominent tags or prolapsing haemorrhoids can make cleansing difficult or sustain contact with stool. Constipation with overflow is another possibility. The objective is a comfortable soft formed stool, not the same high-fibre instruction for every patient: extra fibre may help a constipated person but a patient with excessive loose stool needs a different assessment. Ask about urgency, leakage, discharge, bleeding and changed bowel habit so that a dermatological complaint does not obscure an anorectal disorder.
Inflammatory dermatoses include irritant and allergic contact dermatitis, eczema, psoriasis and lichen sclerosus. Look beyond the anus when the appearance suggests a broader skin disease: scalp or nail changes can support psoriasis, while ivory-white anogenital skin, purpura, fissuring and scarring suggest lichen sclerosus. Genital and perianal involvement may form a figure-of-eight distribution. A focal persistent nodule, thickening or ulcer in such skin needs prompt reassessment even if background itching is well controlled. A mild steroid used for an episode of dermatitis is not an adequate substitute for a diagnosis-specific lichen sclerosus treatment and surveillance plan.
Infection is another distinct pathway. Candida, dermatophytes, streptococcal infection and selected sexually transmitted infections can cause local symptoms. Threadworms are more characteristic in children but can affect adults, particularly with nocturnal symptoms or household exposure. The pattern and appropriate specimens should support treatment. An antifungal is not a universal anti-itch medicine, and a positive culture must be interpreted with the clinical lesion because colonisation may coexist with another primary dermatosis. Persistent symptoms should lead to renewed examination rather than serial unselected creams.
Key points
- Pruritus ani is a symptom: examine the perianal skin and relevant anorectal findings before choosing treatment.
- Stool leakage, sweating, rubbing and over-cleansing can maintain an itch–scratch cycle; reduce irritants and aim for soft formed stool.
- A persistent unexplained anal ulcer or mass needs a direct referral decision and must not be hidden by repeated empiric steroid courses.
- Use a short mild topical steroid only for a diagnosed suitable inflammatory dermatosis after infection and ulceration have been excluded.
- Treat a demonstrated fungal dermatosis with the appropriate antifungal; the selected plain hydrocortisone product contraindicates infected skin.
- Recheck skin and symptoms after treatment, and investigate persisting contact allergy, bowel disease, atypical lesions or another diagnosis.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Irritants and moisture
Stool residue, mucus, sweat, friction and repeated cleansing can injure the perianal barrier, especially when leakage or local anatomical folds retain moisture.
Specific skin or anorectal disease
Contact allergy, eczema, psoriasis, lichen sclerosus, infection and anorectal pathology can cause or amplify itching through distinct mechanisms.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Barrier breakdown
Irritated skin becomes more vulnerable to moisture and chemical exposures, allowing ordinary cleansing or stool contact to become painful or itchy.
- 2Itch and scratch cycle
Scratching produces excoriation and inflammation, which increases itch and can lead to lichenification, fissuring and sleep disruption.
- 3Allergic sensitisation
A delayed contact reaction to a preservative or therapeutic ingredient can maintain dermatitis despite the patient’s intention to relieve the original symptoms.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Record soaps, wipes, perfumed paper, barrier preparations, local anaesthetics, prescribed creams, condoms and lubricants. Establish the order in which symptoms and treatments appeared. An agent introduced to relieve the itch may now be maintaining it through irritation or contact allergy.
Document erythema, maceration, scale, excoriations, lichenification, fissures, plaques, ulcers and focal induration. Redness can be less conspicuous in darker skin, so texture, symptoms and comparison with surrounding tissue also matter. Do not label a persistent focal lesion as simple scratching without reassessment.
With consent, inspect relevant genital skin and other affected areas when lichen sclerosus, psoriasis, eczema or hidradenitis is possible. Ask about itch elsewhere, joint or bowel symptoms and the effect on sleep and intimacy. Explain why broader examination helps distinguish the cause.
Consider an appropriate digital examination and anoscopy where leakage, haemorrhoidal prolapse, a mass or a fistula is suspected. Active pain may require a more tolerable specialist examination. Look for stool staining but avoid equating it with poor hygiene or assuming it explains every lesion.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Skin microscopy culture and appropriate scrapingFirst step - Why
- Assess a suspected bacterial or fungal contribution before diagnosis-specific therapy.
- Interpretation and limitations
- A swab can identify bacterial or yeast infection; an active scaly edge may be sampled for dermatophytes. PCDS recommends swabbing patients in its pruritus assessment, whereas BAD describes additional tests selected after examination. Interpret the organism with the morphology and course rather than treating every isolate as the sole cause.
- 02
Patch testing for persistent contact allergy - Why
- Investigate a suspected delayed allergy when symptoms persist despite sensible avoidance and treatment.
- Interpretation and limitations
- Specialist testing can identify an allergen in a wipe, preservative or therapeutic product. A relevant positive result needs to match an actual exposure. It does not exclude concurrent leakage, eczema or another local disease.
- 03
Selected biopsy or specialist lesion assessment - Why
- Clarify atypical persistent tissue or suspected neoplasia.
- Interpretation and limitations
- An unexplained anal mass or ulceration supports a direct suspected cancer referral consideration under NG12 without waiting for FIT. In lichen sclerosus, new focal thickening, persistent erythema, ulceration or bleeding warrants prompt specialist review and tissue assessment as indicated.
- 04
Bowel investigations driven by associated findings - Why
- Investigate a luminal or functional cause when the history and examination support it.
- Interpretation and limitations
- Bleeding, changed bowel habit, a rectal mass, fistula symptoms or unexplained leakage may justify a colorectal pathway. Do not send every otherwise typical irritant rash for colonoscopy, but do not let a skin diagnosis cancel a concerning bowel presentation.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Candidal or dermatophyte disease
A compatible rash and appropriate microbiological findings support fungal disease, while an isolated organism without the matching lesion may represent colonisation.
Lichen sclerosus and psoriasis
Ivory-white scarring or a characteristic inflammatory pattern elsewhere helps distinguish these dermatoses from uncomplicated irritant eczema.
Anorectal or cutaneous neoplasia
A persistent focal ulcer, induration or mass can present with itch and needs its own diagnostic assessment even alongside a common inflammatory rash.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Worked caseRemove a demonstrated contact triggerFirst stepA 50-year-old woman has three months of itching and soreness despite using cleansing wipes and several creams.+
- 1Examination shows eczematous perianal skin without an ulcer, fungal morphology, anal mass or features of lichen sclerosus. Stool is formed and there is no leakage. Appropriate skin samples do not identify infection. Specialist patch testing identifies a preservative present in her wipes, providing a relevant exposure-linked diagnosis of allergic contact dermatitis.
- 2She stops the implicated wipes and fragranced preparations, cleans gently with lukewarm water and pats dry. For the diagnosed noninfected dermatitis, she uses the selected hydrocortisone acetate 1% cream sparingly on external affected skin twice daily for an agreed seven-day course, with plain barrier care and a scheduled review. The prescription excludes mucosal application, ulcerated skin and ongoing infection, and she receives fabric-fire and worsening-skin advice.
- 3At one week the erythema and excoriation have substantially improved and the steroid is stopped. She maintains allergen avoidance and simple skin care rather than restarting the original products as soon as the itching recedes. Any new focal ulcer, bleeding or marked deterioration would trigger reassessment.
- 4At four weeks she sleeps without scratching, the skin is intact and there is no recurrent dermatitis. The recorded endpoint is improvement after removal of a demonstrated exposure with resolution on examination; the positive patch test alone was not treated as proof of successful management.
02Barrier and bowel careReduce repeated local irritationThe assessment supports moisture or irritant-related symptoms without a suspicious lesion.+
- 1Clean gently after bowel opening with lukewarm water and avoid rubbing, perfumed wipes, disinfectants and multiple unneeded topical products. Pat dry and use comfortable breathable clothing. Discuss how to reduce prolonged moisture while respecting the person’s work, mobility and continence needs.
- 2Use a simple emollient or barrier preparation suited to the skin and the patient’s preference. Address constipation, diarrhoea or leakage specifically, aiming for formed stool without straining. A brief food-and-symptom diary can test an individual suspected trigger without imposing broad unnecessary dietary exclusions.
- 3EscalationIf an inflammatory dermatosis is confirmed, select an appropriate short topical treatment and review response. Avoid repeated potent-steroid escalation for undifferentiated itch. Markedly white scarred skin or persistent focal disease needs its own diagnosis and treatment plan rather than continued generic barrier care alone.
03Diagnosed infection or persistent symptomsChoose treatment from the demonstrated causeAlternativeItch continues or examination and specimens identify a specific alternative mechanism.+
- 1For clinically compatible candidal dermatitis, the selected clotrimazole 1% cream is applied thinly to affected external skin two or three times daily for at least two weeks; dermatophyte infections require at least a month under its SmPC. Review the response and the diagnosis if symptoms do not improve. Do not add the selected plain hydrocortisone to infected skin.
- 2For bacterial infection, threadworms or a sexually transmitted infection, confirm the relevant pathway and treat the condition and any indicated contacts. A fungal cream will not cover these diagnoses. A painful collection or systemic illness changes the urgency from skin symptom control to source assessment.
- 3If treatment fails, check adherence, persistent exposure, skin sampling and the original morphology. Consider patch testing, a dermatology or colorectal opinion, or biopsy according to the unresolved finding. A persistent unexplained anal ulcer or mass should not wait through repeated empiric treatment cycles.
Key medicines and prescribing safety2 treatments · regimens, roles and cautions+
Sovereign hydrocortisone acetate 1% cream
For a confirmed suitable noninfected perianal dermatitis in an adult, apply a small amount sparingly to affected external skin twice daily; the selected SmPC permits two or three applications daily. The worked case uses seven days followed by review and stopping if resolved. Do not apply inside the anal canal or use an occlusive dressing.Exclude hydrocortisone or excipient hypersensitivity. Do not use on bacterial, viral or fungal skin infection, ulcers or local infection; urticaria and rosacea are also excluded. Avoid use for psoriasis under this SmPC. Prolonged or extensive treatment and moist/flexural or damaged skin increase absorption, atrophy and systemic steroid risk. No specific renal/hepatic adjustment is provided; keep treatment limited and review vulnerable patients. Pregnancy safety is inadequately established, so obtain an individual benefit-risk decision; no neonatal problems are documented for nursing mothers. Stop and reassess worsening infection, marked irritation, rebound burning or visual disturbance. No known interactions are listed. Paraffin-contaminated clothing or dressings burn more readily: avoid smoking and naked flames.
Cooper clotrimazole 1% skin cream
Apply a thin even layer to the affected external skin two or three times daily and rub in gently. A half-centimetre strip covers roughly a hand-sized area. Treat candidal skin infection for at least two weeks and dermatophyte infection for at least one month; reassess a nonresponding or uncertain lesion.Exclude clotrimazole or excipient hypersensitivity; do not use to treat scalp or nail infection. Cetostearyl alcohol and benzyl alcohol can cause local irritation or contact allergy. Avoid eyes and oral use. The product has no separate age schedule and no specified renal/hepatic adjustment; use only the indicated cutaneous formulation. Pregnancy use requires physician or midwife supervision; use during lactation is permitted. Latex contraception may be damaged, so use alternative precautions during treatment and for at least five days afterwards. Keep contaminated fabrics away from cigarettes and flames, and stop for a significant allergic or irritant reaction.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Excoriation and secondary infection
Repeated scratching can break the skin and create painful fissures or a secondary infection that changes the appearance and treatment requirements.
Sleep and quality-of-life impairment
Chronic itching can disrupt sleep, concentration, intimacy and confidence despite a relatively small affected area of skin.
Treatment-related skin injury
Repeated or inappropriate topical steroid use can produce atrophy, rebound inflammation or spread of infection, particularly on sensitive flexural skin.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Review itch, sleep disturbance and skin integrity, recording whether the provoking exposure or leakage has actually changed.
- Reassess after the agreed short steroid course and avoid automatic repeats when the original dermatitis has resolved.
- Check fungal treatment response, adherence and local irritation, and reconsider colonisation or an alternative diagnosis if the appearance does not improve.
- Ensure a patient with lichen sclerosus or another chronic dermatosis has appropriate follow-up and understands the need to report new thickening, ulceration or bleeding.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Diagnosis before potency
A stronger steroid is not a substitute for knowing whether the lesion is eczema, infection, lichen sclerosus or neoplasia.
Preservatives can perpetuate symptoms
A treatment tube or cleansing wipe may contain the relevant allergen; the complete exposure list matters as much as the original trigger.
Explain the product distinction
A cream licensed for dermatitis can have a warning against undifferentiated pruritus. State the actual diagnosed indication rather than assuming all hydrocortisone products have identical instructions.
Judge the combined endpoint
Reduced itch, restored sleep, intact skin and control of leakage or a contact trigger together provide a more useful outcome than a temporary reduction in redness.
11Common pitfallsFrequent interpretation and management errors.
- 01
Over-cleansing with wipes, soaps or antiseptics can maintain inflammation even when the patient is trying carefully to improve hygiene.
- 02
Using a steroid on an undiagnosed fungal eruption can suppress the appearance while leaving the cause untreated.
- 03
Treating a positive swab without examining the lesion can mistake colonisation for the explanation of chronic symptoms.
- 04
Repeated symptom suppression can delay biopsy or referral of a persistent focal ulcer, mass or changing lichen sclerosus lesion.