Post-inflammatory hyperpigmentation occurs as brown macules or patches, often with a poorly defined border, irregular in outline and usually with little surface change [ 1 ] . The basic mechanism in response to various triggers (see 'Aetiology', below) is melanosis of the epidermal or dermal layer of the skin. A number of inflammatory mediators, including prostanoids, cytokines and chemokines as well as reactive oxygen species, are released during the inflammatory process in the epidermal layer. These stimulate melanocytes to increase the production of melanin. In dermal melanosis, inflammation disrupts the basal layer, causing melanin to be released and trapped in the macrophages of the papillary dermis - a process with the delightful name of pigmentary incontinence [ 2 ] .