• Cellulitis is an infection of the epidermis/dermis and subcutaneous tissues.
• Cellulitis is a common reason for emergency department visits.
• Most patients can be managed with oral antibiotics.  Frequently, patients and some clinicians have the expectation that they require intravenous antibiotics to treat the cellulitis.  IV antibiotics treatments clog already crowded EDs, take up nursing and physician and patient time and expose nurses to the risk of needle stick injury.

• Most cases of cellulitis are caused by either staphylococcus aureus or streptococcus species.
• Skin cultures are not helpful.
• Cultures usually not helpful for cellulitis or diabetic foot infections.
• Beware of infections over joints (septic arthritis).
• Beware of hand infections (tenosynovitis – which requires plastic surgery consultation).
• Ultrasound in cellulitis can help to diagnose deep abscesses.
• Oral clindamycin is absorbed as well as IV – no need for IV unless vomiting or toxic.
• Initial management should be with cephalexin 500 mg PO QID for 5-7 days. Allergic patients can be treated with clindamycin 300 mg PO tid x 5-7 days.

• If patients are systemically unwell (sepsis – 2 or more SIRS criteria: HR > 90/min; RR > 20/min; T > 38 degrees C), they may require intravenous antibiotics, but many can still be managed as outpatients. Ceftriaxone 2 grams IV q 24hr or cefazolin 2 grams IV given with 1 gram of PO probenecid (to prolong renal excretion of cefazolin) are reasonable choices.

Special situations:

• Diabetic foot: (cellulitis on areas of body are treated as in non-diabetic patients):
  • Oral: Moxifloxacin 400 mg PO once daily x 7 days
  • IV: Ertepenem 1 gram IV q 24 hr until improvement, then step down to oral.
• Bites: (animal/human): Clavulin 500 mg PO TID x 7 days
• Salt water: (vibrio vulnificans) Ciprofloxacin 500 mg PO BID x 7 days
• Fresh water: (aeromonas hydrophila) Ciprofloxacin 500 mg PO BID x 7 days
• Injection drug user (high risk for MRSA):
  • Oral: Doxycycline 100 mg PO BID x 7 days; (or Septra DS 1 PO BID x 7 days)
  • IV: Vancomycin – weight/renal function based

• Most cases of cellulitis can be managed as an outpatient.
• Patients who are elderly, have multiple co-morbidities, or are unable to return to hospital on a daily basis for IV treatment (if required) may need admission.
• Patients with severe cellulitis and/or sepsis may require admission to hospital.

• If there is a suspicion of possible necrotizing fasciitis (see Necrotizing Fasciitis – Diagnsosis), transfer to a facility with surgical capabilities and ICU is required.

• Suspicion of necrotizing fasciitis necessitates early referral to surgery/plastic surgery.
• Vasculopathic patients (DM, PVD) with severe cellulitis in the leg/foot need referral to vascular surgery.
• Patients not improving/worsening after several days of treatment or patients in whom unfamiliar antibiotics may be indicated will benefit from an infectious diseases consult.
• Ophthalmologic referral for patients with suspected orbital cellulitis.

• Completion of antibiotic prescriptions provided to patients should be emphasized.
• Improvement in erythema and pain is slow and lags behind bacterial cure; tell patients that symptoms will not improve for at least 36 hours following initiation of antibiotics.

1. Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of America

   
   

2. Interventions for cellulitis and erysipelas – cochrane.org

   
   

1. Aboltins CA, Hutchinson AF, Sinnappu RN, Cresp D, Risteski C, Kathirgamanathan R, Tacey MA, Chiu H, Lim K. Oral versus parenteral antimicrobials for the treatment of cellulitis: a randomized non-inferiority trial. J Antimicrob Chemother. 2015 Feb;70(2):581-6. doi: 10.1093/jac/dku397. Epub 2014 Oct 21.