Cellulitis and skin infections

    • Cellulitis is a spreading infection of the skin extending to involve the subcutaneous tissues. The most common causes are group A ß -haemolytic streptococci (GABHS) andStaphylococcus aureus. Predisposing factors include skin abrasions, lacerations, burns, eczematous skin, etc, although the portal of entry of organisms is often not seen.
    • Allergic reactions / contact dermatitis (e.g. to insect bites, immunisations, plants, etc) are frequently misdiagnosed as cellulitis. If there is itchiness and no tenderness, cellulitis is unlikely.
    • Erysipelas is a specific superficial form of cellulitis usually caused by GABHS. There may be lymphatic involvement.
    • Impetigo (commonly called "school sores") is a highly contagious infection of the epidermis, particularly common in young children. Causative organisms are GABHS and S. aureus.
    • Staphylococcal scalded skin syndrome (SSSS) is a blistering skin disorder induced by the exfoliative (epidermolytic) toxins ofS. aureus. It primarily affects neonates and young children.
    • Necrotising fasciitis is a rapidly progressive soft tissue infection characterised by necrosis of subcutaneous tissue. Aetiology is often polymicrobial. Causative organisms include GABHS, S. aureus and anaerobes. It can cause severe illness with a high mortality rate (~25%).
    • Consider herpetic infection when vesicles are present, and send appropriate specimens for immunofluorescence and viral culture.

    There are many other forms of skin infection that are not covered in this guideline.


    The typical presenting features of all skin infections include soft tissue redness, warmth and swelling, but other features are variable (see table and photos below). It is difficult to distinguish between skin infections caused by GABHS and S. aureus on a clinical basis alone.

      Tenderness Fever Exudate, crusting Systemic symptoms HR up,
    BP down
    Cellulitis +/- +/- +/- +/- -  
    Erysipelas + +/- +/- + +/- Well-defined border
    Impetigo - +/- ++ - - May be bullous
    SSSS + + ++ +/- +/-  
    Necrotising fasciitis ++ + +/- ++ ++

    Thrombo-cytopenia may be present

    Often tender beyond area of skin changes

    Allergic reaction /
    Contact dermatitis
    - +/- - - - Often itchy.
    May see insect bite.


    Cellulitis pic 1

    Cellulitis pic 2


    Staphylococcal scalded skin syndrome


    Cellulitis pic 3


    Cellulitis pic 4

    photo courtesy of Dr Jonathan Carapetis

    Contact dermatitis (allergic reaction)


    Cellulitis pic 5


    photo courtesy of Prof Mike South


    • Swab for Gram stain (slide) and culture if discharge present
    • FBE + blood culture if systemic systemic symptoms present. Low yield.
    • ESR, xrays +/- bone scan if osteomyelitis suspected (See Osteomyelitis / Septic arthritis guidelines)
    • Ultrasound if fluctuance present
    • Surgical opinion if necrotising fasciitis or abscess suspected



    Flucloxacillin 25 mg/kg (max 500mg) po 6H for 7 days


    Cephalexin 25mg/kg po 6H for 7 days

    If severe/extensive, systemically unwell or not responding to oral treatment

    flucloxacillin 50 mg/kg (max 2g) iv 6H
    (consider adding clindamycin if rapidly progressive to inhibit toxin production)

    For facial/periorbital cellulitis: consider adding Ceftriaxone 50 mg/kg/dose (2g) iv 12H if: < 5yo and non-Hib immunised, or not responding to flucloxacillin alone
    (See Periorbital cellulitis guidelines)


    (uncomplicated localised): wash crusts off - topical mupirocin 2% ointment 8H

    If extensive / multiple lesions present / not responding to topical treatment: treat as for cellulitis

    Impetigo is very contagious - the child should be excluded from child care /kinder / school until treatment has started and the sores are completely covered with watertight dressings (eg Tegaderm).

    Provide Parent Information Sheet on Impetigo.

    Necrotising fasciitis

    flucloxacillin 50 mg/kg (max 2g) iv 6H PLUS
    clindamycin 10 mg/kg (max 600 mg) iv 6H

    Urgent referral to surgical team for debridement


    Parent Information sheet (HTML version)

    Information specific to RCH

    For children with uncomplicated cellulitis requiring IV antibiotics, consider admission under Hospital-In-The-Home (HITH) directly from the Emergency Department. Refer to HITH and start IV ceftriaxone 50mg/kg daily.

    • Children with associated sepsis, orbital cellulitis or necrotising fasciitis are not appropriate for HITH admission.
    • Infants <6 months of age and children with other co-morbidities including immunosuppression, can also be considered for HITH admission.