The world is full of people of all creed and races and it is a common fact that people from certain races have different skin colours to people from other races. But other than the range of normal skin colours, there are certain skin colours that can occur with specific medical conditions.
The most common reason for a change in skin colour is a suntan, which damages the skin and causes darkening of the skin (hyperpigmentation). However, some diseases are also known to cause hyperpigmentation, such as Addison’s disease or haemochromatosis.
The converse is lightening of the skin (hypopigmentation) and can happen with diseases such as leprosy, vitiligo or albinism. Alternatively, people can look pale when they are anaemic or extremely frightened, triggering a sympathetic nervous response, shutting down blood circulation to the face and extremities.
It is common to see red skin with flushing, sunburns, skin infections or numerous dermatological conditions such as rashes. Occasionally, these rashes may be associated with serious diseases such as lupus or Crohn’s disease.
Cyanosis (literally “blueness” in Latin) causes the skin to bluish-purple and it is due to the lack of oxygen in the blood. This could be caused by any number of reasons that causes hypoxia. For example, babies can be born with a heart defect that causes mixing of oxygenated and deoxygenated blood, leading to something called “blue baby syndrome”.
Liver dysfunction can present as jaundice, which is yellowing of skin and the white of the eyes due to a build-up of bilirubin.
Some stranger skin changes can be caused by certain chemicals. Carrots contain beta-carotene (which gives carrots their orange colour) and excess consumption can cause carotenosis (or carotenodermia), a yellowing of the skin. Eating too many tomatoes causes a similar condition called lycopenodermia, which presents as reddened skin (lycopene gives tomatoes their red colour). A combination of the two produces a distinctively orange colour. Both conditions are harmless and disappear after reducing the amount of carrots and tomatoes eaten.
Even stranger still is a condition called argyria, which can be caused by exposure to silver, either through medications especially alternative medicine), mining or contamination of the water supply. Silver causes skin to turn a deep blue colour and the pigmentation is irreversible. Similarly, copper can turn skin green and gold can turn skin grey.