What is the most likely diagnosis and appropriate management for a burning, pruritic, erythematous, scaly rash that started on the wrists and is spreading proximally up the arms?

Burning, Itchy Red Scaly Rash Beginning at Wrists and Spreading Up Arms

Most Likely Diagnosis: Contact Dermatitis (Irritant or Allergic)

The clinical presentation of a burning, pruritic, erythematous, scaly rash starting at the wrists and spreading proximally is most consistent with contact dermatitis, which should be managed with immediate identification and avoidance of the causative agent, combined with mid- to high-potency topical corticosteroids. 1

Key Diagnostic Features Supporting Contact Dermatitis

• Contact dermatitis characteristically presents with erythematous and pruritic skin lesions with visible borders after contact with a foreign substance 1
• The wrist is a classic location for contact dermatitis due to frequent exposure to jewelry (nickel), watches, elastic bands, soaps, and occupational irritants 2
• Irritant contact dermatitis patients typically report burning and stinging sensations in excess of pruritus, which matches this presentation 3
• The proximal spreading pattern suggests continued exposure or spread of the irritant/allergen along the arms 4
• Scaling and erythema are hallmark features of both irritant and allergic contact dermatitis 1

Critical Life-Threatening Exclusions First

Before proceeding with contact dermatitis management, you must exclude Rocky Mountain Spotted Fever (RMSF), which can be fatal:

• RMSF typically begins with small (1-5 mm) blanching pink macules on ankles, wrists, or forearms appearing 2-4 days after fever onset 5
• However, fewer than 50% of RMSF patients develop rash in the first 3 days, and up to 20% never develop a rash 5
• The CDC recommends initiating doxycycline 100 mg twice daily immediately if ANY of the following are present: fever + rash + headache + tick exposure or endemic area exposure 5
• The case-fatality rate for RMSF is 5-10%, with 50% of deaths occurring within 9 days of illness onset 5, 6

If the patient has fever, headache, myalgias, or any systemic symptoms, treat empirically for RMSF immediately without waiting for laboratory confirmation. 5

Diagnostic Algorithm

Step 1: Assess for systemic symptoms

• Check for fever, headache, severe myalgias, or altered mental status 5
• If present → treat immediately for RMSF with doxycycline 100 mg twice daily 5
• If absent → proceed to Step 2

Step 2: Obtain detailed exposure history

• Ask specifically about new jewelry, watches, elastic bands, gloves, soaps, detergents, occupational exposures, or topical products applied to wrists/arms in the past 2-4 weeks 4, 1
• Determine if symptoms improve with removal from suspected exposure 1
• Occupational history is critical, as contact dermatitis accounts for 95% of occupational skin disorders 3

Step 3: Examine rash characteristics

• Well-demarcated borders with erythema and scaling strongly suggest irritant contact dermatitis 3
• Vesicles or bullae in acute cases suggest allergic contact dermatitis 1
• Lichenification with cracks and fissures suggests chronic contact dermatitis 1

Step 4: Differentiate irritant vs. allergic contact dermatitis

• Irritant contact dermatitis: burning/stinging predominates over itching, well-demarcated lesions, occurs on first exposure 3
• Allergic contact dermatitis: itching predominates, requires prior sensitization, delayed hypersensitivity reaction 1
• Both can coexist and present similarly 3

Immediate Management

Step 1: Remove the causative agent

• Complete avoidance of suspected irritants or allergens is essential 4
• This includes both removal from the environment and promotion of metabolism/expulsion of absorbed allergens 4

Step 2: Initiate topical corticosteroids

• For localized acute allergic contact dermatitis, use mid- or high-potency topical steroids such as triamcinolone 0.1% or clobetasol 0.05% twice daily 1
• Relief should occur within 12-24 hours 1
• Continue for 1-2 weeks until resolution 1

Step 3: Consider systemic corticosteroids if extensive

• If the rash involves greater than 20% body surface area, systemic steroid therapy is required 1
• Use oral prednisone 40-60 mg daily 1
• Taper over 2-3 weeks to prevent rebound dermatitis 1

Step 4: Restore skin barrier

• Apply emollients liberally and frequently to restore barrier function 4
• Use fragrance-free, hypoallergenic moisturizers 4

Step 5: Symptomatic relief

• Oral antihistamines for pruritus (sedating antihistamines at bedtime may be helpful) 4, 7
• Cool compresses for acute weeping lesions 1

When to Perform Patch Testing

• If the diagnosis or specific allergen remains unknown after treatment failure, patch testing should be performed 1
• Patch testing is beneficial for diagnosing contact dermatitis caused by metals (nickel, cobalt, chromium, gold), topical medications, rubber chemicals, and fragrances 7
• Readings at 48,72, and 96 hours are standard 2
• Negative patch testing does not exclude irritant contact dermatitis, which is diagnosed by exclusion 3

Critical Pitfalls to Avoid

• Do not assume absence of fever excludes RMSF—up to 40% of patients report no tick bite history, and rash may be absent or atypical 5
• Do not use rapid steroid tapers (less than 2 weeks) for extensive contact dermatitis, as this causes rebound dermatitis 1
• Do not overlook occupational exposures—obtain detailed work history including use of gloves, chemicals, and protective equipment 3
• Do not assume negative patch testing rules out contact dermatitis—it only excludes allergic contact dermatitis, not irritant contact dermatitis 3
• Do not confuse contact dermatitis with atopic dermatitis or psoriasis—contact dermatitis has well-demarcated borders and clear temporal relationship to exposure 4, 3
• Do not miss systemic contact dermatitis—if topical avoidance fails, consider systemic exposure through diet (nickel in foods) or medications 7

Expected Clinical Response

• Improvement should be seen within 24-48 hours of starting topical corticosteroids and avoiding the causative agent 1
• Complete resolution typically occurs within 1-2 weeks 1
• If no improvement occurs within 3-5 days, reconsider the diagnosis and perform patch testing 1
• Chronic cases may require 2-3 weeks of treatment 1

Alternative Diagnoses to Consider if Treatment Fails

• Psoriasis: characterized by well-demarcated erythematous plaques with silvery scale, often symmetric, may involve extensor surfaces 8
• Atopic eczema: typically involves flexural areas, associated with personal/family history of atopy, less well-demarcated borders 8
• Lichen planus: violaceous, polygonal, flat-topped papules with Wickham striae, often involves wrists but typically more purple than red 4
• Cutaneous T-cell lymphoma: persistent erythematous patches/plaques unresponsive to topical steroids, requires biopsy 8