Causes of Illness and Disease in Pre-modern Britain (c.500-1800)

Miasma theory: The dominant belief was that diseases were caused by ‘bad air’, a theory known as miasma. This led to efforts to clear rubbish and maintain cleanliness.
Astrology: People believed that the position of stars and planets influenced health. If someone was ill, it was often attributed to an unfavorable celestial alignment.
Supernatural causes: Religious beliefs played a big role in health assumptions. Illnesses were often considered a punishment from God, or the work of witches or demons.
Imbalanced humours: Ancient Greek theory of the four humours (blood, phlegm, black bile, yellow bile) persisted. Illness was thought to be caused by an imbalance in these body fluids.

Causes of Illness and Disease in the Industrial Age (1800-1900)

Miasma theory continues: The concept of diseases being caused by bad air persisted until the 19th century, resulting in public health acts to improve sanitation.
Germ theory: In the late 19th century, Louis Pasteur’s germ theory gained acceptance, establishing that microbes cause illness. This revolutionized health and medicine.
Industrial pollution: Rapid industrialization led to pollution, poor living conditions, and overcrowded factories, contributing to the spread of disease.

Lifestyle factors: Today, it’s recognised that smoking, diet, alcohol, and lack of exercise play vital roles in the cause of diseases such as heart disease, diabetes, and cancer.
Genetics and inheritance: Genetic issues are now known to cause a host of illnesses and conditions, like Down syndrome, cystic fibrosis, and inherited cancers.
Environmental factors: Increasing attention is paid to how environmental factors and exposure to harmful substances can lead to diseases like asthma, lung cancer, and mesothelioma.
Germs and viruses: The understanding and acceptance of germs, bacteria, and viruses as causes of disease continue, leading to advancements in vaccinations and antibiotics.