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Description of Medical Condition

An acute, spreading infection of the dermis and subcutaneous tissue. Several entities are recognized:

  • Cellulitis of the extremities — characterized by an expanding, red, swollen, tender or painful plaque with an indefinite border that may cover a wide area
  • Recurrent cellulitis of the leg after saphenous venectomy — patients have an acute onset of swelling, erythema of the legs arising months to years after coronary artery bypass. (Surgery using lower extremity veins for bypass grafts.)
  • Dissecting cellulitis of the scalp — recurrent painful, fluctuant dermal and subcutaneous nodules
  • Facial cellulitis in adults — a rare event. Patients usually develop pharyngitis, followed by high fever, rapidly progressive anterior neck swelling, tenderness and erythema associated with dysphagia.
  • Facial cellulitis in children — potentially serious. Swelling and erythema of the cheek develop rapidly, usually unilateral.
  • Perianal cellulitis — bright perianal erythema extending from the anal verge approximately 2 to 3 cm onto the surrounding perianal skin
  • Pseudomonas cellulitis — may be a localized phenomenon or it may occur during pseudomonas septicemia


System(s) affected: Skin/Exocrine

Genetics: No known genetic pattern

Incidence/Prevalence in USA: Unknown

Predominant age:

  • Perianal cellulitis — principally in children
  • Facial cellulitis — in adults, usually older than 50 years. In children, between 6 months and three years.

Predominant sex: Male = Female (perianal cellulitis more common in boys)

Medical Symptoms and Signs of Disease


  • Local tenderness
  • Pain
  • Erythema
  • Malaise
  • Fever, chills
  • Involved area is red, hot, and swollen
  • Borders of the area are not elevated and not demarcated
  • Regional lymphadenopathy is common

Recurrent cellulitis

  • Same as above
  • Edema
  • High fever, chills and toxicity

Dissecting cellulitis of the scalp

  • Purulent drainage from burrowing interconnecting abscesses

Facial cellulitis in adults

  • Malaise
  • Anorexia
  • Vomiting
  • Itching
  • Burning
  • Dysplasia
  • Anterior neck swelling

Facial cellulitis in children

  • Irritability
  • Upper respiratory tract infection symptoms

Perianal cellulitis

  • Intense perianal erythema
  • Pain on defecation
  • Blood streaked stools
  • Perianal pruritus

What Causes Disease?

By site

  • Cellulitis of the extremities: Group A streptococcus, Staphylococcus aureus
  • Recurrent cellulitis of the leg: Non-group A beta hemolytic Streptococci (group C,G,B)
  • Dissecting cellulitis of the scalp: Staphylococcus aureus
  • Facial cellulitis in adults: H. influenzae type B
  • Facial cellulitis in children: H. influenzae type B, over 3 years with portal of entry:
    • staphylococcal and streptococcal
  • Synergetic necrotizing cellulitis: Mixed aerobic-anaerobic flora
  • Intravenous drug use: Staphylococcus aureus. Streptococci, Enterobacteriaceae, Pseudomonas, Fungi
  • Synergetic necrotizing cellulitis: Mixed aerobic-anaerobic flora

Specific diseases

  • Diabetes mellitus: Staphylococcus aureus.

Streptococci, Enterobacteriaceae, Anaerobes

  • Human bites: Eikenella corrodens
  • Animal bites (cat and dog): Staphylococci, Pasteurella multocida

Patient groups

Oneonates: Group B streptococcus Olmmunocompromised

  • Bacteria (Serratia, Proteus and other Enterobacteriaceae)
  • Fungi (Cryptococcus neoformans)
  • Atypical mycobacterium
  • Children with nephrotic syndrome: E. coli
  • Environmental and occupational exposures
  • Erysipelothrix rhusiopathiae

Vibrio species

  • Aeromonas hydrophilia

Rare causes

  • Anaerobic
  • Clostridium perfringens (gas forming cellulitis)
  • Tuberculosis
  • Syphilitic gumma
  • Fungal: Mucormycosis, Aspergillosis

Risk Factors


  • Previous trauma (laceration, puncture, human or animal bite)
  • Underlying skin lesion (furuncle, ulcer)
  • Surgical wound
  • Recurrent cellulitis
  • Post coronary artery bypass in patients whose saphenous veins have been removed
  • Lower extremity lymphedema secondary to a) radical pelvic surgery b) radiation therapy c) neoplastic involvement of pelvic lymph nodes
  • Mastectomy
  • Diabetes mellitus
  • Intravenous drug use
  • Immunocompromised host
  • Burns
  • Environmental and occupational factors

Diagnosis of Disease

Differential Diagnosis

Perianal cellulitis OCandida intertrigo

  • Psoriasis
  • Pinworm infection
  • Inflammatory bowel disease
  • Behavioral problem
  • Child abuse


  • Acute gout
  • Fasciitis/myositis
  • Mycotic aneurysm
  • Ruptured Baker’s cyst
  • Thrombophlebitis
  • Osteomyelitis OHerpetic whitlow
  • Cutaneous diphtheria
  • Pseudogout


  • Aspirates from the point of maximum inflammation. Yield a 45% positive culture rate as compared to a 5% from leading edge culture.
  • Blood cultures — potential pathogens isolated in 25% of patients
  • Mild leucocytosis with a left shift
  • A mildly elevated sedimentation rate
  • CBC

Drugs that may alter lab results: Previous antibiotic therapy may alter the results

Disorders that may alter lab results: N/A

Pathological Findings

Biopsy of skin shows marked infiltration of the dermis with eosinophils and inflammatory changes

Special Tests

  • Serial serological testing with antistreptolysin 0, anti-deoxyribonuclease B, and anti-hyaluronidase tests may be successful in diagnosing cellulitis caused by group A, C, or G hemolytic streptococci
  • Sinus drainage and culture of aspirate


Gas forming cellulitis

  • Plain x-rays show gas bubbles in the soft tissue
  • CT shows gas and myonecrosis

Diagnostic Procedures

  • Skin biopsy
  • Lumbar puncture should be considered for all children with H. influenzae type B cellulitis

Treatment (Medical Therapy)

Appropriate Health Care

Outpatient for mild cases, inpatient for severe infections

General Measures

  • Immobilization and elevation of the involved limb to reduce swelling may be needed in H. influenzae type B
  • Sterile saline dressings to decrease local pain
  • Moist heat to localize the infection
  • Cool aluminum acetate (Burow’s solution) compresses for pain relief

Surgical Measures

  • Debridement for gas/purulent collections
  • Intubation or tracheotomy may be needed for cellulitis of the head or neck
  • Hand infections — wide filleting incision in necrotizing cellulitis


Ambulatory in mild infection; bedrest in severe infection


Regular diet

Patient Education

  • Good skin hygiene
  • Avoid skin traumas
  • Report early skin changes to physician

Medications (Drugs, Medicines)

Drug(s) of Choice

Treat 10-30 days. Guided by culture results whenever possible.

  • Mild early suspected streptococcal etiology: Aqueous penicillin G, 600,000 U, then IM procaine penicillin at 600,000 Uq8-12hrs
  • Staphylococcal infection or no clues to etiology: penicil-linase-resistant penicillin (e.g., oxacillin 0.5-1.0 g poq6 hrs)
  • Severe infection: penicillinase-resistant penicillin (e.g. nafcillin 1.0-1.5 g IV q4 hrs)
  • Gram negative bacillus as possible etiology: aminogly-coside (gentamicin) plus a semisynthetic penicillin
  • Rapidly progressive cellulitis after a fresh water injury: penicillinase-resistant penicillin plus gentamicin or chloramphenicol
  • Human bites: amoxicillin-clavulanate (Augmentin)
  • Animal bites (cellulitis at the saphenous site): penicillin or nafcillin, in high dosage, IV for 7 days before switching to oral therapy
  • Facial cellulitis in adults and children: (H. influenza B) cefotaxime IV
  • Gas forming cellulitis: Aqueous penicillin G 10-20 million U/day IV
  • Diabetes mellitus: Cefoxitin or if toxic, clindamycin and gentamicin
  • Intravenous drug abuse: Vancomydn and gentamicin
  • Compromised hosts: clindamycin and gentamicin
  • Burn patients: vancomycin and gentamicin

Contraindications: Allergies to the antibiotic

Precautions: Renal failure, other organ failure

Significant possible interactions: Refer to manufacturer’s literature

Alternative Drugs

Mild infection

  • Penicillin allergy: erythromycin, 500 mg po q6 hrs

Severe infection

  • Vancomycin 1.0-1.5 g/day IV
  • Human bite and animal bites: IV cefoxitin

Gas forming cellulitis

  • Metronidazole 500 mg IV q6h
  • Clindamycin 600 mg IV q8h

Fluoroquinolones (adults)

Patient Monitoring

  • A blood culture at the end of treatment to ensure cure
  • Repeat needle aspirate culture
  • Repeat blood count if patient was toxic
  • Repeat lumbar puncture in case of meningitis

Prevention / Avoidance

  • Treatment of tinea pedis with antifungal (such as clotrimazole) will prevent recurrent cellulitis of the legs in patients who have had coronary bypass
  • Avoid trauma
  • Avoid swimming in fresh water or salt water in the presence of skin abrasion
  • Avoid human or animal bite
  • Support stocking with peripheral edema
  • Good skin hygiene
  • For recurrent cellulitis — prophylactic penicillin G (250-500 mg po bid)
  • H. influenzae cellulitis — rifampin prophylaxis for entire family of index case or in day-care classroom in which one or two children exposed. Dosage: 20 mg/kg/day (maximum: 600 mg/day) for 4 days.

Possible Complications

  • Bacteremia
  • Local abscesses
  • Super infection with gram negative organisms
  • Lymphangitis especially in recurrent cellulitis
  • Thrombophlebitis of lower extremities in older patients
  • Dissecting cellulitis of the scalp — scarring; alopecia
  • Facial cellulitis in children — meningitis in 8% of patients
  • Gas forming cellulitis — gangrene; amputation; 25% mortality

Expected Course / Prognosis

With adequate antibiotic treatment, outlook is good


Associated Conditions

Facial cellulitis in children

  • Upper respiratory tract infection
  • Unilateral or bilateral otitis media in 68% of patients
  • Meningitis in 8% of patients

Perianal cellulitis

  • Pharyngitis may precede the infection

Frontal sinus in adult OSubacute bacterial endocarditis

  • Scarlet fever
  • Vaccinia
  • Herpes simplex
  • Herpes zoster

Age-Related Factors

Pediatric: N/A

Geriatric: In cellulitis of lower extremities, patients are more prone to develop thrombophlebitis



International Classification of Diseases

682.9 Cellulitis and abscess at unspecified site

See Also

Cellulitis, periorbital & orbital Erysipelas Animal bites Thrombophlebitis, superficial

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