What antibiotic regimen and home‑care instructions should I give a patient with cellulitis, including dosing, MRSA risk, allergy alternatives, limb elevation, dressing, activity limits, warning signs, and special considerations for diabetes or immunosuppression?

Cellulitis Patient Instructions

Antibiotic Regimen

For typical uncomplicated cellulitis, prescribe a beta-lactam antibiotic for exactly 5 days if clinical improvement occurs—extending only if warmth, tenderness, or erythema have not improved. 1

First-Line Oral Options (Choose One)

• Cephalexin 500 mg orally every 6 hours 1
• Dicloxacillin 250–500 mg orally every 6 hours 1
• Amoxicillin 500 mg orally three times daily 1

These achieve 96% clinical success because beta-hemolytic streptococci and methicillin-sensitive Staphylococcus aureus cause the vast majority of cases. 1, 2

When to Add MRSA Coverage

Add MRSA-active antibiotics ONLY when specific risk factors are present: 1

• Visible purulent drainage or exudate 1
• Penetrating trauma or injection drug use 1
• Known MRSA colonization or prior MRSA infection 1
• Systemic inflammatory response syndrome (fever >38°C, heart rate >90, respiratory rate >24) 1
• Failure to respond to beta-lactam after 48–72 hours 1

If MRSA coverage is needed, use: 1

• Clindamycin 300–450 mg orally every 6 hours (single-agent coverage for both streptococci and MRSA, but only if local MRSA clindamycin resistance <10%) 1, 3
• Trimethoprim-sulfamethoxazole 1–2 double-strength tablets twice daily PLUS cephalexin or amoxicillin (combination required because TMP-SMX lacks reliable streptococcal coverage) 1, 3
• Doxycycline 100 mg orally twice daily PLUS a beta-lactam (never use doxycycline alone; it misses streptococci) 1

Penicillin Allergy Alternatives

• For non-immediate reactions: Cephalexin remains safe (cross-reactivity only 2–4%) 1
• For true penicillin allergy: Clindamycin 300–450 mg every 6 hours (if local resistance <10%) 1, 3

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Home Care Instructions

Limb Elevation (Critical and Often Neglected)

Elevate the affected extremity above heart level for at least 30 minutes three times daily. This promotes gravity drainage of edema and inflammatory substances, hastening clinical improvement. 1

Activity Limits

• Rest the affected area during the first 48–72 hours 4
• Avoid strenuous activity until warmth and tenderness resolve 1
• Return to normal activity gradually once symptoms improve 1

Dressing and Wound Care

• Keep the area clean and dry 1
• If purulent drainage is present, the primary treatment is incision and drainage—not antibiotics alone 1, 3
• Cover any open wounds with clean, dry dressings 1

Pain Management

• Ibuprofen 400 mg every 6 hours for 5 days may hasten resolution of inflammation and reduce pain 5
• Avoid NSAIDs in patients with renal impairment or gastrointestinal bleeding risk 5

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Warning Signs Requiring Immediate Medical Attention

Return to the emergency department or call your doctor immediately if you develop: 1

• Severe pain out of proportion to the appearance (suggests necrotizing infection) 1
• Rapid expansion of redness despite antibiotics 1
• Fever, confusion, or altered mental status 1
• Skin blisters, blackening, or areas that feel "wooden-hard" 1
• Numbness or loss of sensation in the affected area 1
• Hypotension or dizziness 1

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Special Considerations

Diabetes

• Diabetic foot infections require broader antimicrobial coverage than simple cellulitis 1
• For mild diabetic foot cellulitis: amoxicillin-clavulanate 875/125 mg twice daily 1
• For moderate infections: ceftriaxone, ampicillin-sulbactam, or ertapenem 1
• For severe infections: piperacillin-tazobactam, imipenem-cilastatin, or vancomycin plus ceftazidime 1
• Maintain optimal blood glucose control to improve infection clearance 1
• Avoid systemic corticosteroids in diabetic patients—diabetes is an absolute contraindication 1

Immunosuppression

• Immunocompromised patients have specific MRSA risk factors that mandate empirical MRSA-active therapy regardless of purulence 1
• Consider hospitalization for severe immunocompromise or neutropenia 1
• Broader-spectrum IV antibiotics (vancomycin plus piperacillin-tazobactam) are often required 1

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Preventing Recurrence

Address predisposing conditions to reduce recurrence risk (annual recurrence rates are 8–20%): 1

• Examine interdigital toe spaces for tinea pedis (athlete's foot), fissuring, scaling, or maceration—treating these eradicates colonization 1
• Manage venous insufficiency with compression stockings once acute infection resolves 1
• Treat chronic edema and lymphedema 1
• Control obesity and eczema 1

For patients with 3–4 episodes per year despite treating predisposing factors, consider prophylactic antibiotics: 1

• Penicillin V 250 mg orally twice daily 1
• Erythromycin 250 mg orally twice daily 1

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Follow-Up

Reassess within 24–48 hours to verify clinical response—treatment failure rates of 21% have been reported with some oral regimens. 1 If no improvement after 48–72 hours, consider resistant organisms (MRSA), undrained abscess, deeper infection, or alternative diagnoses. 1

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Common Pitfalls to Avoid

• Do not routinely add MRSA coverage for typical cellulitis without specific risk factors—this represents overtreatment and increases resistance 1
• Do not use doxycycline or TMP-SMX as monotherapy for typical cellulitis; they lack reliable streptococcal coverage 1, 3
• Do not automatically extend therapy to 7–10 days; extend only if warmth, tenderness, or erythema persist after 5 days 1
• Do not delay surgical consultation when signs of necrotizing infection are present—these progress rapidly and require debridement 1
• Residual redness after completing antibiotics does not automatically indicate ongoing infection—inflammation may persist for 1–2 weeks while tissue remodels 1