A 4-year-old child presents with a fever and a red and swollen foot (Figure 103-1). The patient injured her foot 3 days before with a door. On physical examination, the foot was warm, tender, red, and swollen, and the child’s temperature was 39.4°C (103°F). This is classic cellulitis and the child was admitted for IV antibiotics.

Cellulitis is an acute infection of the skin that involves the dermis and subcutaneous tissues.

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  In one review of serious skin infections in children admitted to a hospital in New Zealand, the most common types of infection were cellulitis (38%) and subcutaneous abscesses (36%).¹ The most frequent sites of infection were the head, face and neck, (32%) and lower limbs (32%). The most frequently isolated organisms were Staphylococcus aureus (48%) and Streptococcus pyogenes (20%).¹

  
  
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  Facial cellulitis occurs more often in children ages 6 months to 3 years.

  
  
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  Perianal cellulitis occurs more commonly in young children (see Chapter 95, Diaper Rash and Perianal Dermatitis).

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  Often begins with a break in the skin caused by trauma, a bite, or an underlying dermatosis (e.g., atopic dermatitis) (Figures 103-1 to 103-4).

  
  
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  Is most often caused by group A β-hemolytic Streptococcus (GAS) (Figure 103-3) or Staphylococcus aureus. The most common etiology of cellulitis with intact skin, when it has been determined through needle aspiration and/or punch biopsy, is S. aureus, outnumbering GAS by a ratio of nearly 2:1.²

  
  
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  There are increasing concerns about the role of community-acquired methicillin-resistant S. aureus (MRSA) in all soft-tissue infections including cellulitis.^3–6

  
  
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  After a cat or dog bite, cellulitis is often caused by Pasteurella multocida (Figure 103-4).

  
  
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  After saltwater exposure, cellulitis can be secondary to Vibrio vulnificus in warm climates. A Vibrio vulnificus infection can be especially deadly.

  
  
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  Erysipelas is a specific type of superficial cellulitis with prominent lymphatic involvement and leading to a sharply defined and elevated border (Figures 103-5 and 103-6).

  
  
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  Risk factors for hospitalization for staphylococcal skin infections in children in California were age less than 3 years, being Black, and lacking private insurance.⁷