What is cellulitis?

Cellulitis is an acute suppurative bacterial infection of the skin and soft tissue, often with involvement of underlying structures: fascia, muscles and tendons.

Causes of cellulitis

It is most often due to B haemolytic streptococci or Staphylococcus aureus.
Less common causes include:

  • Anaerobic bacteria
  • Mycobacteria
  • Proteus
  • Pseudomonas
  • Crytococcus (rarely)
  • It usually (but not always) follows some discernible wound.
  • It is often a complication of immunosuppression like diabetes and HIV/AIDS.


The prevalence is unclear. It is commoner in adult males above 45 years of age and young children.

Risk factors for cellulitis

Risk factors include:

  1. Immunosuppression,
  2. Malnutrition,
  3. Obesity,
  4. Elderly persons,
  5. Peripheral vascular disease
  6. Lymphoedema and recent injuries to the skin.

Symptoms of cellulitis

  1. Areas of oedema; rapidly spreading
  2. Erythema (rapidly becomes intense and spreads)
  3. Tenderness and warmth: Often accompanied by fever, lymphangitis, regional lymphadenitis
  4. Systemic signs of toxicity
  5. Area becomes infiltrated and pits on pressure
  6. Sometimes the central part becomes nodular and surrounded by a vesicle that ruptures
    and discharges pus and necrotic material

Differential diagnoses

Complications of cellulitis

Complications are unusual in immunocompetent adults. Children and compromised adults are at higher risk.

The following are the complications of cellulitis:

  1. Septicaemia
  2. Gangrene
  3. Metastatic abscesses
  4. Recurrent cellulitis may predispose to chronic lymphoedema


  • Blood culture
  • Full Blood Count with differentials
  • Fasting blood glucose
  • HIV screening
  • Wound swab for microscopy, culture and sensitivity
  • Urinalysis

Treatment for cellulitis

Treatment objectives

  1. Eradicate infection
  2. Treat underlying immune suppression
  3. Prevent complications

Drug treatment


Adult: 500mg-1 g orally every 6 hours for 5-7 days


  • under 5 years: a quarter adult dose;
  • 5 – 10 years: half adult dose



Adult: 500 mg orally every 6 hours for 5-7 days


  • under 5 years: a quarter adult dose;
  • 5 – 10 years: half adult dose


Adult: 250-750 mg orally every 12 hours for 5 – 7days

Child: Ciprofloxacin is contraindicated in children.


Adult: 1 g intravenously or intramuscularly daily for 3 days


  • Neonate, 20-50 mg/kg by intravenous infusion over 60 minutes;
  • 1 month – 12 years, body weight less than 50 kg: 50 mg/kg by deep intramuscular injection or intravenous injection over 2-4 minutes, or by intravenous infusion
    • Intramuscular injections over 1 g should be divided over more than 1 site.
    • Doses of 50 mg/kg and more should be given by intravenous infusion only.
    • Use only when there is significant resistance to other drugs

Tetanus Prophylaxis

Surgical treatment

  • May need incision and drainage or debridement

Caution, contraindications

  • Ciprofloxacin is contraindicated in growing adolescents and children below 12 years; also contraindicated in pregnancy

How to prevent cellulitis

Treat any wound promptly.

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