Medieval Medicine: Wrong Ideas, Deadly Results (c.1250-c.1500)

Medieval doctors had two main theories to explain disease, and both were completely wrong.

The Four Humours

Based on the ancient Greek physician Galen (who lived in the 2nd century AD), medieval doctors believed the body contained four fluids called humours: blood, phlegm, yellow bile, and black bile. If these were balanced, you were healthy. If they were unbalanced, you became ill. Treatments therefore aimed to re-balance the humours — so doctors would bleed patients, make them vomit, or give them laxatives.

Miasma Theory

Miasma theory held that disease spread through foul-smelling air — "bad air" (from the Italian mala aria). People believed the smell of rotting matter, sewage, or corpses caused illness. This was completely wrong about the mechanism, but it accidentally led to some good advice — people did avoid smelly places, which sometimes happened to be where disease actually spread.

The Role of the Church

The Catholic Church dominated medieval life and had enormous influence on medical thinking. The Church taught that disease was God's punishment for sin, and that prayer and penance were essential treatments. It also controlled the universities where doctors trained — which meant that questioning Galen's teachings was seen as going against authority. This created a powerful barrier to new ideas.