What is the best approach to evaluate and manage itchiness of the scalp in a patient with no visible lesions?

Evaluation of Scalp Itchiness Without Visible Lesions

Begin with a systematic 2-week trial of high lipid-content emollients to exclude asteatotic eczema, while simultaneously conducting a focused history and targeted laboratory workup to identify systemic, neuropathic, or psychogenic causes. 1, 2

Initial Clinical Assessment

History Taking - Key Elements to Elicit

• Duration and pattern: Acute vs. chronic (>6 weeks), constant vs. intermittent 3, 4
• Medication review: Specifically ask about opioids, chloroquine, biologics, and recent medication changes 1
• Travel history: Consider malaria, strongyloidiasis, schistosomiasis if relevant 1
• Systemic symptoms: Weight loss, night sweats, fatigue (malignancy screening), polyuria/polydipsia (diabetes), jaundice (hepatic), or neurological symptoms 1
• Psychiatric history: Depression, anxiety, or somatoform disorders, particularly in elderly women with diabetes 5
• Aggravating factors: Hot water, specific products, stress 2, 4

Physical Examination - Beyond the Scalp

• Examine entire body surface: Look for secondary lesions (excoriations, lichenification) that may indicate chronic scratching elsewhere 6
• Check finger webs, anogenital region, nails: Rule out scabies or other dermatoses 6
• Neurological assessment: If neuropathic etiology suspected (burning quality, allodynia, hyperesthesia) 5
• Lymph node examination: Particularly if malignancy suspected 1

Diagnostic Workup

First-Line Laboratory Investigations

All patients with chronic scalp pruritus without visible lesions should receive: 1

• Complete blood count with differential: Screen for iron deficiency (ferritin), polycythemia vera, lymphoma 1
• Comprehensive metabolic panel: Urea, electrolytes, creatinine (uremia), liver function tests, fasting glucose or A1C 1, 6
• Inflammatory markers: ESR, LDH if hematological malignancy suspected 1

Second-Line Investigations (Based on Clinical Suspicion)

• Thyroid function tests: Only if additional clinical features suggest endocrinopathy - NOT routine 1
• Infectious serology: HIV, hepatitis A/B/C if risk factors present 1
• JAK2 V617F mutation: If polycythemia vera suspected (elevated hemoglobin/hematocrit) 1
• Bile acids and antimitochondrial antibodies: If hepatic disease suspected 1
• Vitamin D level: May be therapeutic target even without deficiency 1

Specialized Testing When Indicated

• Patch testing: Consider if history suggests contact allergen exposure (hair products, dyes, shampoos), though less common with isolated scalp involvement 1
• Skin biopsy: Reserved for persistent, unexplained cases to exclude cutaneous lymphoma or small fiber neuropathy 1
• Neurological referral: If neuropathic features present (burning, dysesthesia, allodynia) - consider cervical spine imaging, trigeminal nerve assessment 1, 5

Management Algorithm

Step 1: Empiric Trial (Weeks 1-2)

Mandatory initial approach regardless of suspected etiology: 2

• High lipid-content emollients: Apply liberally twice daily to entire scalp 2
• Mild topical corticosteroid: Clobetasone butyrate to scalp if asteatotic eczema suspected 2
• Behavioral modifications: Avoid hot water, harsh shampoos, minimize scratching 2

Step 2: Symptomatic Treatment (If Step 1 Fails)

Topical options: 2

• Topical doxepin: Maximum 8 days, <10% body surface area, ≤12g daily 2
• Menthol preparations: Alternative cooling agent 2
• Avoid: Crotamiton cream (Strength B recommendation against), capsaicin, calamine 2

Systemic options: 2

• Non-sedating H1 antihistamines: Fexofenadine 180mg or loratadine 10mg daily as second-line 2
• Combined H1/H2 blockade: Add cimetidine to fexofenadine for enhanced effect 2
• Absolutely avoid sedating antihistamines (hydroxyzine) in elderly due to dementia risk 2

Step 3: Cause-Specific Treatment

If systemic cause identified: 1, 2

• Drug-induced (opioids): Naltrexone if cessation impossible (Strength B), or trial mirtazapine 30mg, gabapentin 1200mg divided 1, 2
• Hepatic pruritus: Rifampicin first-line (Strength A) 2
• Uremic pruritus: Optimize dialysis, normalize calcium-phosphate, BB-UVB phototherapy (Strength A) 2
• Iron deficiency: Iron replacement (Strength C) 1
• Vitamin D deficiency: Supplementation may help even without documented deficiency 1

Step 4: Neuropathic Scalp Dysesthesia

If burning/dysesthetic quality with negative workup: 5

• Gabapentin: Particularly effective in elderly patients and diabetics 2, 5
• Specialist referral: Neurology if central lesions suspected (cervical spine disease, MS, stroke) 1, 5
• Consider: Post-infectious etiology (COVID-19 association recently described) 5

Critical Pitfalls to Avoid

• Do NOT perform routine thyroid or extensive endocrine testing without specific clinical features - low yield and not recommended 1
• Do NOT pursue extensive malignancy workup unless systemic symptoms present - history and physical examination guide targeted investigation 1
• Do NOT use sedating antihistamines in elderly - significant dementia risk (Strength C against) 2
• Do NOT assume psychogenic etiology until thorough systemic and neuropathic evaluation completed 6, 4
• Do NOT overlook medication review - drug-induced pruritus is common and reversible 1

When to Refer

• Hematology: If polycythemia vera or lymphoma suspected 1
• Hepatology: If significant hepatic impairment identified 1
• Neurology: If neuropathic features with central nervous system signs 1, 5
• Dermatology: If persistent after 4-6 weeks of appropriate management or diagnostic uncertainty 4