Generalized Itching in Adults

Introduction to Causes and Diagnosis

The British College of Dermatology recommends that in a 40-year-old with generalized itching, the most common causes are iron deficiency, followed by chronic kidney disease, liver disease, thyroid disorders, hematological malignancies, and drug reactions 1
Generalized pruritus without visible rash falls into two main categories: secondary pruritus due to underlying systemic disorder, and generalized pruritus of unknown origin (GPUO) when no cause is identified despite thorough workup 1

Iron deficiency is the single most common systemic cause, accounting for 25% of all cases with underlying disease, and iron replacement can lead to complete cessation of pruritus shortly after starting therapy 1
Iron overload (haemochromatosis or hyperferritinaemia) can also cause generalized itching 1, 2
Uraemic pruritus occurs in patients with renal impairment, often associated with xerosis (dry skin) 3, 4
Cholestatic liver disease is a key cause of generalized itching 3
Polycythaemia vera is characterized by aquagenic pruritus (triggered by water contact) 2
Hodgkin lymphoma can cause pruritus, often with night sweats, fever, and weight loss, in up to 30% of patients 2
Solid tumors can cause paraneoplastic pruritus 3
HIV, hepatitis B and C can cause generalized itching 3

All patients with chronic generalized pruritus require full blood count, ferritin levels, liver function tests, urea and electrolytes, and thyroid-stimulating hormone tests 1, 3
Additional investigations based on clinical suspicion include blood film, lactate dehydrogenase, ESR, JAK2 V617F mutation, HIV and hepatitis serology, and tissue transglutaminase antibodies 2, 3

The British College of Dermatology recommends starting with emollients and self-care advice before investigating, including keeping nails short, applying emollients liberally and frequently, and a short trial of non-sedating antihistamine 5
Cause-specific treatment includes iron replacement therapy for iron deficiency, venesection or desferrioxamine for iron overload, and cytoreductive therapy for polycythemia vera 3, 2
Referral to secondary care is recommended when diagnostic doubt exists, the patient is distressed despite primary care management, or symptoms persist after appropriate initial treatment 5, 6

In a 40-year-old, always check iron studies first as iron deficiency is the most treatable and common systemic cause 1
Aquagenic pruritus strongly suggests polycythemia vera 2
Night itching with B symptoms suggests lymphoma 2
Never use sedating antihistamines long-term as they may predispose to dementia 3