An abscess is a localized, "walled off," inflammatory process in which white blood cells accumulate at the site of infection in the dermis and/or subcutaneous tissue. The most common cause is a bacterial infection, with the superficial folliculitis being the most common site that then spreads to deeper parts of the dermis and subcutaneous tissue. The most common associated bacterial infection is Staphylococcus aureus. Abscesses may arise from infection of surrounding appendages, direct inoculation at site of injury, or from hematogenous spread. Other causes of abscesses may be secondary to neutrophil dysfunctions and immunological dysfunctions, as seen in hyperimmunoglobulin E syndrome and chronic granulomatous disease.