Tinea nigra is a type of dermatomycosis. A dermatomycosis is a fungal infection of the skin. Tinea nigra affects the outermost layer of skin, called the stratum corneum. Tinea nigra causes a black or brown patch on the skin. Although a patch of tinea nigra may be mistaken for the more serious skin discolorations of melanoma, tinea nigra is actually a very benign condition that often causes no symptoms apart from its appearance.