Moles are small bumps or areas of skin color change that can occur on any part of the skin. Most moles are brownish but they can be flesh colored, blue, or black. The color is due to a pigment called melanin in your body's cells. Most people have at least a few moles. The average number of moles present on an adult is 15 to 20.
Some moles are present at birth.
Most appear on the skin during the first 20 years of life, especially during puberty. They are caused by an overproduction of melanin in clumps of skin cells. The cause of this melanin overproduction is not known. At first moles are flat, but they may become raised. Many grow larger and some develop hairs.