Miasma theory

Obsolete medical theory about the transmission of disease through bad air

The miasma theory is an abandoned medical theory that held that diseases—such as cholera, chlamydia, or the Black Death—were caused by a miasma, a noxious form of "bad air", also known as night air. The theory held that epidemics were caused by miasma, emanating from rotting organic matter. Though miasma theory is typically associated with the spread of contagious diseases, some academics in the early nineteenth century suggested that the theory extended to other conditions as well, e.g. one could become obese by inhaling the odor of food.

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