What is the differential diagnosis (ddx) and treatment for facial pruritus (itching) and redness?

Differential Diagnosis of Facial Pruritus and Redness

For facial pruritus and redness, prioritize dermatologic causes first—including contact dermatitis, atopic dermatitis, rosacea, and seborrheic dermatitis—before investigating systemic etiologies, as localized facial symptoms rarely represent generalized pruritus requiring extensive workup. 1

Primary Dermatologic Differential

Common Inflammatory Conditions

• Contact dermatitis (allergic or irritant): Look for exposure to cosmetics, jewelry, detergents, or topical products; distribution often corresponds to allergen contact pattern 2, 1
• Atopic dermatitis: History of atopy, xerosis, and eczematous changes; more common in patients with personal or family history of allergic conditions 1
• Seborrheic dermatitis: Greasy, yellowish scales in seborrheic distribution (eyebrows, nasolabial folds, scalp); associated with erythema and pruritus 2
• Rosacea: Persistent facial erythema with flushing episodes, telangiectasias, and possible papulopustular lesions; typically affects central face 3

Other Dermatologic Causes

• Photodermatosis: Erythema and pruritus in sun-exposed areas; temporal relationship with UV exposure 3
• Xerotic eczema: Dry, scaly skin with pruritus; particularly common in elderly patients 4, 1

Systemic Causes (When Facial Symptoms Are Part of Generalized Pruritus)

Hematologic Disorders

• Polycythemia vera: Aquagenic pruritus (triggered by water exposure) is highly suggestive; facial flushing may occur; JAK2 V617F mutation present in up to 97% of cases 5, 3
• Iron deficiency or overload: Check ferritin, iron, and TIBC 5
• Hodgkin lymphoma: Associated systemic symptoms include weight loss, night sweats, fever, and lymphadenopathy 4, 6

Hepatic and Renal Causes

• Cholestatic liver disease: Jaundice, elevated alkaline phosphatase, gamma-GT, and bile acids; pruritus often precedes jaundice 7, 5
• Uremia: Elevated creatinine and BUN; typically occurs in patients with known chronic kidney disease 4, 6

Endocrine and Metabolic

• Thyroid disease: Hyperthyroidism can cause pruritus and flushing; check TSH 6, 1
• Diabetes mellitus: Check fasting glucose or hemoglobin A1C 5
• Carcinoid syndrome: Episodic flushing with diarrhea, wheezing; requires 24-hour urinary 5-HIAA 3

Drug-Induced

• Medication review is essential: 20-30% of generalized pruritus cases have identifiable causes, including drug reactions 5, 6
• Common culprits include opioids, ACE inhibitors, and biologics 4

Infectious Causes

• HIV infection: Consider in appropriate risk contexts 6, 1
• Hepatitis A, B, C: Check serology if risk factors present 7

Diagnostic Approach

Initial Assessment

• Detailed history: Medication review (including over-the-counter products and cosmetics), onset and duration, triggers (water, heat, specific products), associated systemic symptoms (weight loss, night sweats, jaundice) 5
• Skin examination: Identify primary versus secondary lesions; look for scratch-induced changes like lichen simplex chronicus 1
• Distribution pattern: Localized facial involvement suggests dermatologic cause; generalized involvement warrants systemic workup 5

First-Tier Laboratory Testing (If Systemic Cause Suspected)

• Complete blood count with differential 5
• Comprehensive metabolic panel (including liver function tests, creatinine, BUN) 4, 5
• Thyroid-stimulating hormone 5, 6
• Fasting glucose or hemoglobin A1C 5
• Iron studies (ferritin, iron, TIBC) 5

Second-Tier Testing (Based on Clinical Suspicion)

• If polycythemia vera suspected: JAK2 V617F mutation 5
• If cholestasis suspected: Alkaline phosphatase, gamma-GT, bile acids, antimitochondrial antibodies 7, 5
• If malignancy suspected: Chest radiography, CT imaging 5
• If infection suspected: HIV serology, hepatitis panel 7, 5

Skin-Specific Testing

• Skin scraping or culture: If fungal infection suspected 1
• Patch testing: If allergic contact dermatitis suspected 1
• Skin biopsy: If diagnosis unclear or bullous pemphigoid suspected (particularly in elderly) 4, 5

Treatment Algorithm

First-Line Dermatologic Management

• Emollients: Maintain skin hydration; high lipid content preferred in elderly 4, 7
• Topical corticosteroids:
  • Hydrocortisone 1% for mild cases: Apply to affected area 3-4 times daily 2
  • Triamcinolone acetonide 0.1% cream for moderate inflammatory dermatoses 8
  • Use for 2 weeks initially in elderly to exclude asteatotic eczema 4, 5
• Avoid irritants: Discontinue potential allergens (cosmetics, fragrances, harsh soaps) 2

Second-Line Therapies

• Non-sedating antihistamines: Fexofenadine or loratadine for symptomatic relief 7
• Topical doxepin or menthol preparations: For refractory pruritus 7

Systemic Disease-Specific Treatment

Polycythemia Vera-Associated Pruritus

• Cytoreductive therapy, aspirin 300 mg daily, interferon-α, SSRIs, cimetidine, or atenolol 4, 7
• UVB phototherapy or PUVA for refractory cases 4, 7

Cholestatic Pruritus

• Rifampicin (first-line), cholestyramine (second-line), sertraline (third-line) 7
• Avoid gabapentin in hepatic pruritus 7

Uremic Pruritus

• Optimize dialysis parameters, normalize calcium-phosphate balance 7
• BB-UVB phototherapy (Strength of recommendation A) 7
• Avoid cetirizine and long-term sedating antihistamines except in palliative care 7

Lymphoma-Associated Pruritus

• Cimetidine, carbamazepine, gabapentin, or mirtazapine 4, 7
• Oral corticosteroids for incurable lymphoma 4, 7
• BB-UVB for Hodgkin lymphoma; NB-UVB for non-Hodgkin lymphoma 7

Drug-Induced Pruritus

• Trial of medication cessation if risk-benefit analysis acceptable 4, 7
• Naltrexone for opioid-induced pruritus if cessation not possible 7

Critical Pitfalls to Avoid

• Do not overlook medication history: Drug-induced pruritus is common and reversible; review all medications including over-the-counter products 5, 6
• Do not use long-term sedating antihistamines in elderly: Associated with increased dementia risk 7, 5
• Do not dismiss pruritus in elderly patients: May be first sign of bullous pemphigoid or malignancy 4, 5
• Do not perform extensive systemic workup for clearly localized facial dermatitis: Reserve comprehensive testing for generalized pruritus or when systemic symptoms present 5
• Do not delay referral: Refer to dermatology if diagnostic doubt exists or primary management fails after 2-4 weeks 4, 5

Special Considerations for Elderly Patients

• Initial 2-week trial of emollients plus topical steroids to exclude asteatotic eczema before extensive workup 4, 5
• Consider bullous pemphigoid: Pruritus alone can be presenting feature; may require skin biopsy and indirect immunofluorescence 4
• Moisturizers with high lipid content preferred 4
• Regular follow-up essential when underlying cause not immediately evident 5