A tan line is a visually clear division on the human skin between an area of pronounced comparative paleness relative to other areas that have been suntanned by exposure to ultraviolet (UV) radiation. The source of the radiation may be the sun, or artificial UV sources such as tanning lamps. Tan lines are usually an inadvertent result of a work environment or of recreational activities, but are sometimes intentional. Many people regard visible tan lines as unsightly and seek to avoid tan lines that will be visible when regular clothes are worn.
