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
- Acute mainly pustular localised eruptions
- Chronic mainly pustular eruptions
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
Impetigo
- Rapidly enlarging plaque
- Swab Staphylococcus aureus +/- Streptococcus pyogenes
Impetigo
Furunculosis/boil
- Based on hair follicle
- May lead to abscess formation
- Swab Staphylococcus aureus
Furunculosis
Folliculitis
- Itchy or painful follicular pustules
- Various types
Bacterial folliculitis
Dermatophyte infection
- Kerion: abscess formation
- Due to zoophilic fungus, eg Microsporum canis
Kerion
Thrush
- Intertrigo, oral mucosa
- Superficial pustules that dry out easily
- Swab Candida albicans
Candidal intertrigo
Miliaria
- Sweat rash
Miliaria
Chronic mainly pustular eruptions
Acne
- Face, neck, upper trunk
- Comedones + inflammatory lesions
Acne vulgaris
Acneform eruptions
Acneform eruptions
Scabies
- Irregular pustules on hands and feet
- Burrows between fingers, volar wrists
- Papules axillae, groin
- Generalised itchy rash
Scabies
Dermatophyte infection
- Irregular annular plaque with peripheral scale
- Pustules on feet due to Trichophyton interdigitale
Dermatophyte infections
Palmoplantar pustulosis
- Hands, feet
- Sterile tender, itchy, pustules
Palmoplantar pustulosis
Erosive pustular dermatosis
- Sun damaged scalp
- May develop squamous cell carcinoma
- Lakes of greenish pus
- Culture may reveal Staphylococcus aureus
Many skin conditions present with pustules - see links to more On DermNet in the Related Information Section below.