Mongolian blue spots look just like blue bruising. They are a type of birthmark seen most commonly on the buttocks and lower back area of babies, but can appear on other areas of the body such as the face, hands or limbs. They have a distinct blue grey discolouration. The correct name for them is “congenital dermal melaocytosis”. They are thought to be caused by pigment cells in the skin (melanocytes) being trapped in deeper layers of the skin during embryonic development. These very common skin discolourations affect up to 90% or children from an Asian background. No treatment is required and they will usually disappear at around four years of age. Some larger areas can persist for many years.