Cephalexin Duration for Facial Cellulitis
For an otherwise healthy adult with uncomplicated facial cellulitis and no β‑lactam allergy, prescribe cephalexin 500 mg orally four times daily for exactly 5 days if clinical improvement occurs; extend only if warmth, tenderness, or erythema have not improved within this timeframe. 1, 2
Standard Treatment Regimen
Cephalexin 500 mg orally every 6 hours (four times daily) is the preferred oral beta‑lactam for uncomplicated facial cellulitis, providing consistent drug levels against beta‑hemolytic streptococci (especially Streptococcus pyogenes) and methicillin‑sensitive Staphylococcus aureus, the primary pathogens in typical cellulitis 1, 2.
Beta‑lactam monotherapy achieves approximately 96% clinical success in typical non‑purulent cellulitis, confirming that MRSA coverage is usually unnecessary for straightforward cases 1, 2.
Treatment Duration: The 5‑Day Rule
Treat for exactly 5 days when clinical improvement is evident—defined as resolution of warmth and tenderness, improving erythema, and absence of fever 1, 2.
Extend treatment beyond 5 days only if the infection has not improved within this initial period; do not automatically prolong therapy to 7–10 days based on residual erythema alone, as some inflammation persists even after bacterial eradication 1, 2.
High‑quality randomized controlled trial evidence demonstrates that 5‑day courses are as effective as 10‑day courses for uncomplicated cellulitis, achieving 98% clinical resolution at 14 days with no relapses by 28 days 1.
Traditional 7–14‑day regimens are no longer necessary for uncomplicated cases and promote antimicrobial resistance without improving outcomes 1, 2.
When Cephalexin Monotherapy Is Appropriate
Use cephalexin alone for typical non‑purulent facial cellulitis without drainage, exudate, or systemic signs 1, 2.
MRSA is an uncommon cause of typical cellulitis even in high‑prevalence settings; a landmark randomized trial showed that adding trimethoprim‑sulfamethoxazole to cephalexin provided no additional benefit for uncomplicated cellulitis 1, 3.
Do not add MRSA coverage routinely without specific risk factors, as this represents overtreatment and increases antibiotic resistance 1, 2.
When to Add MRSA Coverage (Facial Cellulitis Requires Extra Caution)
Add MRSA‑active antibiotics only when any of the following risk factors are present:
- Penetrating trauma (e.g., nasal piercing, recent nasal surgery, facial laceration) 1.
- Visible purulent drainage or exudate at the infection site 1.
- Known MRSA colonization or prior MRSA infection 1.
- Systemic inflammatory response syndrome (fever > 38°C, heart rate > 90 bpm, respiratory rate > 24 breaths/min) 1.
- Failure to respond to beta‑lactam therapy after 48–72 hours 1.
If MRSA coverage is required:
- Clindamycin 300–450 mg orally every 6 hours provides single‑agent coverage for both streptococci and MRSA, but use only if local MRSA clindamycin resistance is < 10% 1.
- Alternative combination regimens include trimethoprim‑sulfamethoxazole 1–2 double‑strength tablets twice daily plus cephalexin, or doxycycline 100 mg twice daily plus cephalexin 1.
Special Considerations for Facial Cellulitis
Facial cellulitis warrants closer monitoring because of proximity to critical structures (orbit, sinuses, central nervous system) 1.
Reassess patients within 24–48 hours to verify clinical response; treatment failure rates of approximately 21% have been reported with some oral regimens 1.
If odontogenic origin is suspected (dental abscess, recent dental procedure), consider amoxicillin‑clavulanate 875/125 mg twice daily instead of cephalexin to cover oral anaerobes 1, 4.
Hospitalization Criteria
Admit patients with facial cellulitis when any of the following are present:
- Systemic inflammatory response syndrome (fever, tachycardia, hypotension, altered mental status) 1.
- Signs of orbital or periorbital involvement (vision changes, ophthalmoplegia, proptosis) 1.
- Severe pain out of proportion to examination, skin anesthesia, rapid progression, or "wooden‑hard" tissue suggesting necrotizing infection 1.
- Severe immunocompromise or neutropenia 1.
- Failure of outpatient therapy after 24–48 hours 1.
For hospitalized patients requiring IV therapy:
- Cefazolin 1–2 g IV every 8 hours is the preferred IV beta‑lactam for uncomplicated cellulitis 1.
- For severe cellulitis with systemic toxicity, use vancomycin 15–20 mg/kg IV every 8–12 hours plus piperacillin‑tazobactam 3.375–4.5 g IV every 6 hours 1.
Essential Adjunctive Measures
Elevate the head of the bed to promote gravity drainage of facial edema 1.
Treat predisposing conditions such as nasal trauma, chronic rhinitis, nasal vestibulitis, or dental infections to reduce recurrence risk 1, 2.
Examine for tinea pedis and interdigital toe web abnormalities if lower extremity cellulitis is also present, as treating these eradicates colonization and reduces recurrent infection 1, 2.
Common Pitfalls to Avoid
Do not reflexively extend treatment to 7–10 days based on residual erythema alone; extend only if warmth, tenderness, or erythema have not improved after 5 days 1, 2.
Do not add MRSA coverage routinely for typical facial cellulitis without the specified risk factors 1, 2.
Do not use doxycycline or trimethoprim‑sulfamethoxazole as monotherapy for typical cellulitis, as they lack reliable activity against beta‑hemolytic streptococci 1.
Do not delay surgical consultation if signs of orbital involvement, necrotizing infection, or systemic toxicity develop 1.
Do not use first‑generation cephalosporins like cephalexin for Lyme disease; they are ineffective for erythema migrans 2.