Pustular skin conditions

Author: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, September 2015.

What are pustules?

Pustules are smaller than 5–10 mm, and filled with pus, that is, purulent material composed of inflammatory cells (neutrophils).

  • Pus can indicate bacterial, fungal or viral infection
  • Some pustules are sterile and are due to inflammatory skin disease

This topic provides a differential diagnosis of pustular skin conditions.

Acute mainly pustular generalised eruptions

Generalised pustular psoriasis

  • Febrile illness
  • Annular plaques studded with pustules
Generalised pustular psoriasis

Acute generalised exanthematous pustulosis

  • Febrile illness
  • Drug eruption
  • Diffuse superficial pustules
Acute generalised exanthematous pustulosis (AGEP)

Acute mainly pustular localised eruptions


  • Rapidly enlarging plaque
  • Swab Staphylococcus aureus +/- Streptococcus pyogenes


  • Based on hair follicle
  • May lead to abscess formation
  • Swab Staphylococcus aureus


  • Itchy or painful follicular pustules
  • Various types

Dermatophyte infection

  • Kerion: abscess formation
  • Due to zoophilic fungus, eg Microsporum canis


Candida skin problems


  • Sweat rash

Chronic mainly pustular eruptions


  • Face, neck, upper trunk
  • Comedones + inflammatory lesions

Acneform eruptions

Acneform eruptions


  • Irregular pustules on hands and feet
  • Burrows between fingers, volar wrists
  • Papules axillae, groin
  • Generalised itchy rash

Dermatophyte infection

  • Irregular annular plaque with peripheral scale
  • Pustules on feet due to Trichophyton interdigitale
Dermatophyte infections

Localised pustulosis

  • Hands, feet
  • Sterile tender, itchy, pustules
Palmoplantar pustulosis

Erosive pustular dermatosis

  • Sun damaged scalp
  • Often, underlying squamous cell carcinoma
  • Greenish pus
  • Culture Staphylococcus aureus

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