Skin colour is determined by three main factors:

• Melanin is a dark pigment secreted by specialised cells called melanocytes situated in the deepest layers of the epidermis. Sunlight stimulates the production of melanin and this protects the dermis from the harmful effects of sunlight.
• The amount of blood circulating through the dermis and the extent to which it is oxygenated affect skin colour. We appear paler when we are cold and the blood vessels in the skin are constricted. Conversely, when we are hot and the blood vessels in the skin are dilated, we appear flushed.
• Bile pigments in the blood and carotene in subcutaneous fat can give the skin a yellow colour if they are present in excessive amounts.