Moles occur when cells in the skin grow in a cluster instead of being spread throughout the skin. These cells are called melanocytes, and they make the pigment that gives skin its natural color. Moles may darken after exposure to the sun, during the teen years, and during pregnancy. If a mole changes shape, color or begins to bleed or ooze - it is generally recommended that they be checked in case there is any cancer present.
To remove moles - Dr Gary Young recommends applying 1-2 drops of oregano oil directly on the mole, 2-3 times daily. I have also seen people remove them by applying black cancer salve (the type made with blood root) - however, this can be very painful.