In medieval times, people had a range of different theories about the causes of disease. These were based on their beliefs rather than on science.

God

Religion was a huge part of society in the medieval era. In Saxon times, many Christians believed disease came from God. If someone was not living according to God’s rules, they believed God might send them an illness as punishment.

The supernatural

The Vikings believed that illness was caused by magic. People in medieval times were afraid of being cursed by witches or being made ill by evil spirits or demons. For many people, sudden and unexplained illness or death was most easily explained by someone being the victim of a magical attack.

Bad smells

People realised that they were more likely to get ill living in a town than in the countryside. Towns smelled very bad because of issues with sanitation as well as the filth caused by people living close to their animals. As a result, people believed that it must be the terrible smells of the town that were causing disease. These smells were known as miasma.

The four humours

Doctors believed in the theory of the four humours. This was an idea that went back to the ancient Greeks (such as Galen) and Romans. It said that illness was caused by an imbalance between four liquids found within the body. These liquids were called humours.

The four humours were:

• blood
• phlegm
• yellow bile
• black bile