The expression “to have blue blood” is commonly used to describe someone of noble origin or from a royal family. Today, it symbolizes prestige and high social status, but its roots are much older and tied to European medieval history.
The phrase originates from medieval Spain, where the term “sangre azul” was used. During the period of the Reconquista (711–1492), when Christian Spaniards were fighting against the Muslim Moors from North Africa, Spanish nobles took pride in having a “pure” Christian bloodline, without any mixing with other ethnic groups.
They referred to this as “purity of blood,” and the blue veins visible on their hands and arms were seen as proof of that purity. Over time, “blue blood” became a symbol of social, political, and economic superiority. Today it is mostly used humorously or figuratively, but centuries ago it carried serious weight in aristocratic society.
Why nobles appeared to have “blue veins”
During the Middle Ages, society was clearly divided into classes: the nobility, the clergy, and the common people. While peasants worked outdoors under the sun and had darker, tanned skin, nobles lived in palaces, protected from sunlight. Their much lighter skin made the veins on their arms appear blue.
This blue color became associated with purity and aristocracy, in contrast to the “red blood” of ordinary working people.
In reality, all humans have the same blood color, and the expression has nothing to do with biology. It developed from visible physical differences between aristocrats and the rest of society, eventually becoming a metaphor for nobility and high status.
