💡 Pruritus (itch) is defined as an unpleasant cutaneous sensation provoking the desire to scratch. It may be localized (e.g., eczema, scabies) or generalised (e.g., liver disease, renal failure, haematological malignancy). Persistent or unexplained itch should prompt systemic evaluation.

📝 Clinical History

Onset & Duration: Acute vs chronic, intermittent vs persistent.
Distribution: Localised (limbs, scalp, genitals) or generalised.
Associated Skin Changes: Rash, excoriations, dryness, burrows, plaques.
Systemic Symptoms: Jaundice, weight loss, night sweats, uraemia symptoms.
Exposures: New medications, contact with pets, detergents, recent travel.
PMH: Atopy, liver/renal disease, diabetes, malignancy, psychiatric history.
FH: Atopic disorders, psoriasis, systemic diseases.

🩺 Physical Examination

Dermatological: Look for primary lesions (eczema, psoriasis plaques, urticaria wheals) and secondary changes (excoriations, lichenification).
Systemic:
- Liver disease: Jaundice, hepatomegaly, scratch marks on limbs/back.
- Renal disease: Pallor, uraemic frost, xerosis.
- Haematological: Lymphadenopathy, splenomegaly (lymphoma).
Neurological: Signs of peripheral neuropathy in diabetes or post-herpetic itch.

🔬 Investigations

Basic bloods: CBC, U&E, LFTs, TFTs, fasting glucose, iron studies.
Dermatology-specific: Skin scrapings (scabies), biopsy if uncertain diagnosis.
Imaging: Ultrasound (biliary obstruction), CXR (lymphoma suspicion).
Allergy & Immunology: Patch testing, IgE levels if atopy suspected.

📊 Causes of Pruritus

Cause	Diagnostic Tests	Management
🌿 Atopic Dermatitis	Clinical diagnosis; biopsy rarely	Topical steroids, emollients, antihistamines, tacrolimus if severe
🍂 Allergic Contact Dermatitis	Patch testing; clinical history	Avoid allergen, topical steroids, emollients
🧩 Psoriasis	Clinical, PASI scoring, biopsy if atypical	Topical therapy, phototherapy, systemic agents (methotrexate, biologics)
🐜 Scabies	Skin scrapings, nocturnal itch, burrows	Pemitrethin cream, oral ivermectin, treat contacts, environmental cleaning
🌸 Urticaria	Clinical; allergy testing if trigger suspected	Antihistamines, short steroid course if severe, trigger avoidance
🟡 Liver disease (cholestasis)	LFTs, bilirubin, USS for obstruction	Ursodeoxycholic acid, cholestyramine, transplant in severe cases
💧 CKD (uraemia)	Renal function, dialysis adequacy	Optimise dialysis, emollients, antihistamines, gabapentin
🩸 Iron Deficiency Anaemia	CBC, ferritin	Iron supplementation, investigate source of loss
🍬 Diabetes (neuropathy)	HbA1c, nerve conduction studies	Glycaemic control, capsaicin cream, gabapentin/pregabalin
💊 Drug-induced	Temporal link with new meds	Withdraw culprit drug, antihistamines, corticosteroids if severe

⚠️ Red Flags

Generalised pruritus without rash → may indicate systemic disease (renal, liver, lymphoma).
Pruritus + weight loss/night sweats → consider haematological malignancy.
New-onset severe pruritus in elderly → exclude cholestasis, renal disease, malignancy.

💊 Management Principles

General: Emollients, avoid irritants, keep nails short to reduce excoriations.
Topical: Corticosteroids for dermatitis, calamine lotion, menthol creams for relief.
Systemic: Antihistamines (non-sedating first-line), gabapentin/pregabalin for neuropathic itch.
Treat underlying cause: e.g., H. pylori eradication in IDA, dialysis in CKD, ursodeoxycholic acid in cholestasis.

🧑‍⚕️ Case Vignettes

Case 1: 👩 A 23-year-old student presents with intense nocturnal itching, worse in the webs of her fingers and wrists. Her flatmates also report itching. ✅ Diagnosis: Scabies infestation. 📌 Management: Permethrin cream for patient & close contacts, environmental decontamination.

Case 2: 👨 A 65-year-old man with weight loss and jaundice reports severe generalised itch, worse at night. Exam shows scratch marks on arms and scleral icterus. ✅ Diagnosis: Cholestatic pruritus from obstructive jaundice. 📌 Management: Ursodeoxycholic acid, cholestyramine, and referral for possible ERCP.

📚 References

NICE CKS: Pruritus (2023)
Kumar & Clark’s Clinical Medicine, 10th Edition
British Association of Dermatologists: Pruritus Guidelines

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Pruritis