What is the best treatment approach for a patient with a history of eczema who develops cellulitis?

Treatment of Cellulitis in Patients with Eczema

For a patient with eczema who develops cellulitis, treat with a beta-lactam antibiotic (cephalexin 500 mg four times daily or dicloxacillin 250-500 mg every 6 hours) for 5 days if clinical improvement occurs, while simultaneously managing the underlying eczema with emollients and topical corticosteroids to address the predisposing skin barrier defect. 1, 2

First-Line Antibiotic Selection

Beta-lactam monotherapy is the standard of care for typical uncomplicated cellulitis, with a 96% success rate, even in patients with underlying eczema. 1 The most common pathogens are β-hemolytic streptococci (especially Streptococcus pyogenes) and methicillin-sensitive Staphylococcus aureus, both adequately covered by first-generation cephalosporins or penicillinase-resistant penicillins. 1, 3

Recommended oral regimens include:

• Cephalexin 500 mg orally every 6 hours (four times daily) 1, 4
• Dicloxacillin 250-500 mg every 6 hours 1, 4
• Amoxicillin (alternative option) 1
• Clindamycin 300-450 mg every 6 hours if penicillin-allergic 1, 4

Treatment Duration

Treat for exactly 5 days if clinical improvement has occurred; extend only if symptoms have not improved within this timeframe. 1, 2 Five-day courses are as effective as 10-day courses for uncomplicated cellulitis based on high-quality randomized controlled trial evidence. 1, 2 Do not reflexively extend treatment to 7-10 days based on residual erythema alone, as some inflammation persists even after bacterial eradication. 1

When to Add MRSA Coverage

MRSA is an uncommon cause of typical cellulitis and routine coverage is unnecessary, even in hospitals with high MRSA prevalence. 1, 4 Add MRSA-active antibiotics ONLY when specific risk factors are present: 1, 4

• Penetrating trauma or injection drug use 1, 4
• Purulent drainage or exudate 1, 4
• Evidence of MRSA infection elsewhere or known nasal colonization 1, 4
• Systemic inflammatory response syndrome (SIRS) with fever, tachycardia, or hypotension 1, 4

If MRSA coverage is needed, use:

• Clindamycin 300-450 mg orally every 6 hours (covers both streptococci and MRSA) 1, 4
• Trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily PLUS a beta-lactam 1, 4
• Doxycycline 100 mg twice daily PLUS a beta-lactam 1, 4

Managing the Underlying Eczema

Eczema is a critical predisposing factor for cellulitis that must be addressed to prevent recurrence. 5 Patients with atopic eczema have impaired skin barrier function with dry skin and increased susceptibility to bacterial colonization, particularly Staphylococcus aureus. 5, 6

Essential eczema management measures include:

• Emollients: Apply liberally after bathing to provide a surface lipid film that retards evaporative water loss from the epidermis. 5 These are most effective when applied immediately after bathing. 5

• Topical corticosteroids: Use the least potent preparation required to control the eczema, stopping for short periods when possible. 5 For lichenified eczema, ichthammol 1% in zinc ointment or paste bandages can be particularly useful. 5

• Avoid irritants: Use dispersible cream as a soap substitute rather than soaps and detergents, which remove natural lipid from the skin surface. 5 Avoid woolen clothing next to the skin; cotton is preferred. 5

• Treat secondary bacterial infection: Bacterial infection in eczema is suggested by crusting or weeping. 5 Flucloxacillin is the most appropriate antibiotic for S. aureus, which is the commonest pathogen. 5 Erythromycin may be used with penicillin allergy. 5

Adjunctive Measures to Hasten Resolution

• Elevate the affected extremity above heart level for at least 30 minutes three times daily to promote gravity drainage of edema and inflammatory substances. 1, 4

• Examine interdigital toe spaces for tinea pedis, fissuring, scaling, or maceration, as treating these eradicates colonization and reduces recurrent infection risk. 1, 4

• Address venous insufficiency and lymphedema with compression stockings once acute infection resolves, as these predispose to recurrence. 1, 6

• Consider systemic corticosteroids (prednisone 40 mg daily for 7 days) in non-diabetic adults to reduce inflammation, though evidence is limited. 1, 2

Hospitalization Criteria

Admit patients with any of the following: 1, 4

• Systemic inflammatory response syndrome (fever >38°C, heart rate >90, respiratory rate >24, WBC >12,000 or <4,000) 1
• Hypotension or hemodynamic instability 1
• Altered mental status or confusion 1
• Severe immunocompromise or neutropenia 1
• Concern for deeper or necrotizing infection (severe pain out of proportion to examination, skin anesthesia, rapid progression, gas in tissue, bullous changes) 1

For hospitalized patients, use IV cefazolin 1-2 g every 8 hours or vancomycin 15-20 mg/kg every 8-12 hours if MRSA coverage is needed. 1, 4

Common Pitfalls to Avoid

• Do not routinely add MRSA coverage for typical cellulitis without specific risk factors, as this represents overtreatment and increases antibiotic resistance. 1, 4

• Do not use doxycycline or trimethoprim-sulfamethoxazole as monotherapy for typical cellulitis, as their activity against beta-hemolytic streptococci is unreliable. 1, 4

• Do not confuse cellulitis with eczema flares or contact dermatitis. 3, 7 Cellulitis presents with acute onset of unilateral erythema, warmth, swelling, and tenderness, whereas eczema is typically bilateral, chronic, and pruritic without acute warmth. 5, 3

• Do not overlook herpes simplex infection in eczema patients, which presents with grouped, punched-out erosions or vesiculation and requires oral acyclovir. 5

Prevention of Recurrent Cellulitis

Annual recurrence rates are 8-20% in patients with previous cellulitis, particularly those with predisposing factors like eczema. 1, 6 For patients with 3-4 episodes per year despite treating predisposing factors, consider prophylactic antibiotics: 1

• Oral penicillin V 250 mg twice daily for 4-52 weeks 1
• Oral erythromycin 250 mg twice daily 1
• Intramuscular benzathine penicillin every 2-4 weeks 1

The key to preventing recurrence is aggressive management of the underlying eczema with consistent emollient use, appropriate topical corticosteroids, and avoidance of irritants. 5, 6