Acne can leave brown spots which are caused by pigment cells spilling tiny packets of pigment into the skin. These are called melanosomes. These are then picked up by the body's 'garbage collectors'. The pigment will eventually be removed from the skin. Acne can also leave scars if it has made the skin thinner. This can cause skin to appear more transparent and make it so you can more easily see the blood vessels, giving it a red-brown colour. While the scars are permanent, often the colour diminishes with time. To learn more about acne scars, click here. Richard Thomas