What is the best treatment approach for an adult or child with infected eczema and a history of allergy to amoxicillin (amoxicillin)?

Treatment of Infected Eczema in Patients with Amoxicillin Allergy

For patients with infected eczema and amoxicillin allergy, use erythromycin as the first-line systemic antibiotic while continuing topical corticosteroids and liberal emollient application. 1

Immediate Assessment Priorities

Confirm the infection: Look for clinical signs of secondary bacterial infection including crusting, weeping, pustules, or increased erythema beyond baseline eczema activity. 1 Bacterial infection is the most common cause of deterioration in previously stable eczema. 1

Identify the pathogen: Staphylococcus aureus is the most common bacterial pathogen in infected eczema, followed by β-hemolytic streptococci. 1 Send bacteriological swabs if patients do not respond to initial treatment. 1

Rule out viral superinfection: Examine for grouped, punched-out erosions or vesiculation, which indicate herpes simplex infection (eczema herpeticum)—a medical emergency requiring immediate oral or intravenous acyclovir. 1, 2

First-Line Antibiotic Selection with Penicillin Allergy

Erythromycin is the recommended alternative antibiotic when penicillin allergy (including amoxicillin) is present. 1 This macrolide antibiotic provides coverage against both S. aureus and streptococcal species commonly implicated in infected eczema.

Standard Dosing

• Adults: Erythromycin 250-500 mg four times daily for 7-10 days 1
• Children: Dose according to weight and age-appropriate guidelines 1

Important Caveat

Flucloxacillin would be the first-line choice for S. aureus infection in patients without penicillin allergy. 1, 3, 2 Phenoxymethylpenicillin is preferred if β-hemolytic streptococci are isolated. 1 However, both are contraindicated in your patient with amoxicillin allergy due to cross-reactivity within the penicillin class.

Concurrent Topical Anti-Inflammatory Therapy

Continue or initiate topical corticosteroids during bacterial infection—do not withhold them. 2 The infection requires systemic antibiotics, but the underlying eczema inflammation still needs topical anti-inflammatory treatment.

Topical Corticosteroid Selection

• Adults: Use moderately potent topical corticosteroids applied twice daily to affected areas. 3, 2
• Children and infants: Use only low-potency corticosteroids (hydrocortisone 1%) due to increased risk of systemic absorption and HPA axis suppression. 3
• Sensitive areas (face, neck, flexures, genitals): Avoid very potent corticosteroids regardless of age due to higher risk of skin atrophy. 2

Apply the least potent preparation that controls symptoms, and implement short "steroid holidays" when possible. 2, 4

Essential Emollient Therapy

Liberal emollient application remains the cornerstone of treatment even during infection. 1, 3, 2 Apply emollients at least twice daily to the entire body, not just affected areas. 3

• Use fragrance-free, ointment-based emollients for maximum occlusion. 3
• Apply after bathing to provide a surface lipid film that retards water loss. 2
• Continue emollients even when eczema appears controlled—this has steroid-sparing effects. 3

Managing Pruritus During Infection

Sedating antihistamines may be used short-term at night if sleep is significantly disrupted. 3, 2 Their therapeutic value resides principally in their sedative properties, not direct anti-pruritic effects. 1

Non-sedating antihistamines have little to no value in atopic eczema and should not be used. 1, 2

Critical Pitfalls to Avoid

Never delay systemic antibiotics when infection is clinically evident. Deterioration in previously stable eczema is commonly due to secondary bacterial infection. 1

Do not use topical antibiotics alone for infected eczema. Systemic antibiotics are required for established infection. 1

Never use medium, high, or very potent corticosteroids in infants. The risk of HPA axis suppression is dramatically increased. 3

Avoid oral corticosteroids for infected eczema. They are associated with rebound flares and should only be used to "tide over" acute crises after exhausting all other options. 1, 2

Reassessment Timeline

Reassess after 1-2 weeks to evaluate treatment response. 3 If no improvement or worsening occurs, consider:

• Poor treatment adherence 3
• Unrecognized viral superinfection (eczema herpeticum) 3, 2
• Antibiotic resistance requiring culture-directed therapy 1
• Development of contact dermatitis 1
• Need for specialist referral 3

When to Refer or Escalate

Immediate referral for suspected eczema herpeticum (grouped vesicles, punched-out erosions, sudden deterioration with fever). 2 This is a medical emergency requiring immediate antiviral therapy.

Refer to dermatology if:

• Failure to respond to appropriate systemic antibiotics and optimized topical therapy after 2-4 weeks 1, 3
• Recurrent infections requiring repeated antibiotic courses 5, 6
• Need for systemic immunosuppressive therapy for severe underlying eczema 1, 2