In dermatology, a pustule (Latin: pustula; synonym: pustule; ICD-10 R21: rash and other nonspecific skin eruptions) refers to a pustule on skin or mucosa. It may occur epidermally (epidermis = upper skin) or subepidermally (“located beneath the epidermis”). The contents of the pustule may be infectious or sterile (germ-free).
The pustule belongs to the so-called primary florescences. These are skin changes that are the direct result of a disease.
Pustules can be a symptom of many diseases (see under “Differential diagnoses”).
Course and prognosis: Since pustules can lead to inflammation if left untreated, a dermatologist should be consulted for precise clarification if necessary. Course and prognosis depend on the underlying disease.