The word lentigo simply describes a patch of skin that contains a greater density of cells called melanocytes which produce a dark pigment called melanin. There are many different types of lentigo, but the commonest are caused by the sun – solar lentigos. These are non-cancerous brown spots which are thought to develop in response to sun-exposure, especially in those with fairer skin. They can appear anywhere but tend to form on the face, neck, shoulders and forearms. Unlike freckles they usually appear after the age of 30. The main difference between a freckle and a solar lentigo is that in a freckle only the amount of pigment being produced by melanocytes is increased, rather than the actual number of cells.