What is the next best step for a female patient with a spreading, itchy lesion on her inner left thigh, who has been taking Claritin (loratadine) and Keflex (cephalexin) for a week, with continued symptoms of itching, scratching, and mild drainage?

Management of Spreading Inner Thigh Lesion Despite Antibiotic Therapy

This patient likely has a fungal infection (tinea cruris) rather than bacterial cellulitis, and should be started on topical antifungal therapy while discontinuing the current antibiotics. 1

Clinical Reasoning

The key clinical features pointing away from bacterial cellulitis include:

• Location in the inner thigh (groin area) - a classic site for dermatophyte infections 1
• Prominent itching as the primary symptom - bacterial cellulitis typically presents with pain, warmth, and tenderness rather than pruritus 1
• Failure to respond to appropriate anti-streptococcal/anti-staphylococcal coverage (cephalexin) after one week - bacterial cellulitis should show clinical improvement within 5 days of appropriate therapy 1
• Spreading despite antibiotics - suggests a non-bacterial etiology 1

Immediate Management Steps

Discontinue Current Therapy

• Stop cephalexin - continuing ineffective antibiotics promotes resistance and provides no benefit 2
• Stop Claritin - antihistamines alone are insufficient for fungal infections, though may continue for symptomatic itch relief 1

Initiate Antifungal Treatment

• Start topical antifungal cream (clotrimazole 1% or terbinafine 1%) applied twice daily to affected area and 2-3 cm beyond the visible border 1
• Treat any concurrent tinea pedis (athlete's foot) if present, as this is a common predisposing factor for groin infections 1
• Keep area dry - moisture promotes fungal growth in intertriginous areas 3

Symptomatic Management

• Non-sedating antihistamine (cetirizine 10 mg or loratadine 10 mg daily) for daytime itch control 1
• Low-potency topical corticosteroid (hydrocortisone 1%) may be used sparingly in the groin area for severe itching, but avoid high-potency steroids due to risk of skin atrophy in this location 3
• Avoid scratching - this can cause secondary bacterial superinfection 1

Reassessment Timeline

Evaluate after 2 weeks 1:

• Fungal infections typically show improvement within 1-2 weeks of appropriate antifungal therapy
• If no improvement or worsening, consider alternative diagnoses

Alternative Diagnoses to Consider if No Response

Secondary Bacterial Superinfection

• Look for purulent drainage, increased warmth, or expanding erythema 3
• If present, obtain bacterial culture and consider restarting antibiotics targeting Staphylococcus aureus 1
• MRSA coverage is generally NOT needed for typical cellulitis unless there is purulent drainage, penetrating trauma, or evidence of MRSA elsewhere 1

Drug Reaction

• Symmetric drug-related intertriginous and flexural exanthema (SDRIFE) can occur with beta-lactam antibiotics like cephalexin 4
• Presents with symmetric involvement of flexural areas with prominent itching 4
• However, this typically occurs during or shortly after drug exposure, not before treatment initiation 4

Contact Dermatitis

• Consider if there's been exposure to new soaps, detergents, or topical products 3
• Would expect improvement with topical corticosteroids alone 3

Critical Pitfalls to Avoid

• Do not continue ineffective antibiotics - this promotes resistance without clinical benefit 1, 2
• Do not use high-potency topical steroids in the groin - increased risk of skin atrophy and can worsen fungal infections 3
• Do not assume MRSA coverage is needed - typical cellulitis in immunocompetent patients without purulent drainage responds to beta-lactams targeting streptococci 1
• Do not ignore tinea pedis - untreated foot fungus serves as a reservoir for recurrent groin infections 1

When to Refer to Dermatology

Refer if 1, 3:

• No improvement after 2 weeks of appropriate antifungal therapy
• Diagnosis remains uncertain
• Severe or widespread involvement
• Signs of severe cutaneous adverse drug reaction develop