How to manage an adult patient with itchy rashes and no significant past medical history?

Management of Itchy Rashes in Adults

Start with second-generation H1 antihistamines (fexofenadine 180 mg daily or loratadine 10 mg daily) combined with liberal emollient application as first-line therapy for most itchy rashes in adults without significant past medical history. 1, 2

Initial Clinical Assessment

Distinguish between urticaria (hives) and other rashes by examining weal duration and characteristics:

• Urticaria weals last 2-24 hours and leave no residual marks; physical urticaria weals typically resolve within 1 hour (except delayed pressure urticaria) 1
• If individual weals persist >24 hours, consider urticarial vasculitis and obtain skin biopsy 1
• Look for primary lesions (indicating diseased skin) versus secondary lesions from scratching (excoriations, lichenification) 3
• Examine finger webs, anogenital region, nails, and scalp systematically 3

Obtain targeted history focusing on:

• Timing: acute (<6 weeks) versus chronic (>6 weeks) 1
• Triggers: foods, medications (especially NSAIDs, ACE inhibitors, opioids), physical factors (pressure, cold, heat, water) 1
• Associated symptoms: angioedema, systemic symptoms 1

First-Line Treatment Algorithm

For Urticaria (Hives)

Step 1: Second-generation H1 antihistamines at standard doses 1, 2

• Fexofenadine 180 mg daily OR loratadine 10 mg daily
• These are the mainstay of therapy with over 40% response rate 1

Step 2: If inadequate response after 2 weeks, increase antihistamine dose up to 4-fold 1

• This is common practice when benefits outweigh risks, even above manufacturer's licensed recommendations 1

Step 3: Add H2 antihistamines or leukotriene antagonists 1

• Combine H1 with H2 antagonists (e.g., fexofenadine plus cimetidine) for enhanced effect 2
• Add antileukotrienes for resistant cases 1

Step 4: Consider sedating antihistamine at night only 1

• Use sparingly and short-term due to dementia risk, especially in elderly 2, 4

Avoid oral corticosteroids except for:

• Severe acute urticaria with mouth/airway angioedema (short course only) 1
• Delayed pressure urticaria or urticarial vasculitis (may require prolonged treatment) 1

For Non-Urticarial Itchy Rashes

Topical therapy:

• Apply emollients with high lipid content liberally (at least once daily, preferably multiple times) to restore skin barrier 2, 4
• Topical corticosteroids: Hydrocortisone 1% applied 3-4 times daily for up to 2 weeks for mild inflammation 5; betamethasone valerate 1-3 times daily for more severe cases 6
• Alternative topical agents: Clobetasone butyrate or menthol preparations 2
• Topical doxepin: Maximum 8 days, limit to 10% body surface area, do not exceed 12g daily 4

Avoid:

• Crotamiton cream (Strength B recommendation against) 4
• Topical capsaicin or calamine lotion for generalized pruritus 4

Investigations (Only When Indicated)

For acute urticaria (<6 weeks): No investigations needed unless history suggests specific allergen 1

For chronic urticaria (>6 weeks) not responding to antihistamines: 1, 2

• Complete blood count with differential (to detect eosinophilia, leucopenia)
• Erythrocyte sedimentation rate (usually normal in chronic ordinary urticaria; elevated in vasculitis)
• Thyroid function tests and thyroid autoantibodies (14% have thyroid autoimmunity vs 6% in controls) 1

For generalized pruritus without primary skin lesions (after 2-week trial of emollients/steroids fails): 2, 7

• Liver function tests, urea and electrolytes, thyroid-stimulating hormone
• Fasting glucose or hemoglobin A1C
• Iron studies
• Consider: bile acids, antimitochondrial antibodies if liver disease suspected 2
• Consider: HIV and hepatitis serologies if risk factors present 2

Special testing:

• Patch testing for suspected allergic contact dermatitis: facial/eyelid involvement, flexural neck involvement, vesicular hand lesions, recalcitrant disease, unusual distribution 1
• Autologous serum skin test (ASST) for suspected autoimmune urticaria (30% of chronic urticaria cases) 1

Critical Pitfalls to Avoid

• Do not use long-term sedating antihistamines except in palliative care due to dementia risk 2, 4
• Do not prescribe inadequate quantities of emollients; patients need sufficient amounts for liberal application 4
• Do not miss secondary bacterial infection in scratched skin—look for crusting, weeping, purulent discharge and treat with doxycycline 100 mg twice daily for at least 2 weeks 4
• Do not perform extensive investigations in mild chronic urticaria responding to antihistamines 1
• Do not ignore medication review—drug-induced pruritus accounts for 12-25% of cases 1, 2

When to Escalate

• Refer to dermatology if:

  • Individual weals persist >24 hours (possible urticarial vasculitis) 1
  • No response to optimal antihistamine therapy after 4-6 weeks 1
  • Suspected autoimmune urticaria requiring immunomodulating therapy 1
  • Diagnostic uncertainty requiring biopsy 1

• Consider systemic disease workup in:

  • Patients >60 years with generalized pruritus <12 months duration (heightened malignancy concern) 8, 3
  • Absence of primary skin lesions with persistent generalized itch despite treatment 2, 7