Some street dust or grit may remain in the dermis after an abrasion of the skin over a dirty surface. This often happens in cycling accidents. The dust may remain visible as grey, dark blue or black speckles. The bacteria on these mini-splinters may become a source of recurrent infection.
Dermabrasion is the abrasion of the skin surface with a spinning metal brush, to remove the dust particles and surface irregularities. Local or general anaesthesia are required depending on the surface to be treated.