The colour of the skin is determined by the concentrations of three main pigments: melanin, carotene and haemoglobin.
These are found in the dermis and combine to produce the pigmentation of all surface tissues including the skin, mucous membranes, and even the eyes. Abnormal concentrations of these substances can cause distinctive colour changes in the skin or other visible body tissues and may help in diagnosis certain illnesses or skin conditions.
Melanin is the main factor influencing skin colour and, while people of different ethnicities have similar numbers of melanocytes (cells that produce melanin), the vast array of skin tones are due to the amount of this pigment that is produced by these cells. Low levels of melanin production can create a pale yellow skin colour, whereas large amounts create very black skin. Conditions such as vitiligo that affect melanocytes may create patchy variation in skin tone, or a complete loss of skin pigmentation.
Melanocytes are found in abundance in the mucous membranes, nipples, penis, areola, face, parts of the eye and in the limbs. Melanin protects the body’s cells from ultraviolet radiation damage, which is why sun exposure will usually cause the melanocytes to produce more pigment than usual in order to wrap around the cells’ DNA.
Carotenoids are brightly coloured substances found in carrots, chard, peppers, other vegetables and in egg yolks. Carotene is yellowy-orange in colour and is a powerful antioxidant that helps protect skin cells from oxidative damage. It is transformed in the body into vitamin A, which is essential for vision and good skin health.
An excess of beta-carotene is rare but may cause a yellowy residue to appear around the nose, and in the eyes as sebaceous secretions are used to excrete the unneeded substance. Diets excessively high in beta-carotenes, such as juice fasts sometimes recommended for detoxification, may cause a yellowing of the skin and eyes that can be mistaken for jaundice from liver dysfunction.
Haemoglobin is a molecule in the blood that carries oxygen and, by doing so, lends the skin a reddish-pink colour. Where the haemoglobin is not picking up enough oxygen from the lungs and carrying it around the body, the skin can appear blueish, sallow, or grey. It is in this way that a naturally healthy complexion is connected to circulatory and respiratory health as well as to the health of the actual skin cells.