Why open pores seemed dangerous
Before microbes were understood as causes of infection, many people explained disease through miasma: harmful or foul air thought to carry illness. Some medical thinking treated the skin as a vulnerable boundary. A hot bath could warm and soften it, making its pores seem to open; if pores were openings into the body, contaminated air might pass through them.
The reasoning joined an ordinary sensation to an invisible threat. Warm water reddens skin and can leave it feeling exposed, while pores are real openings associated with sweat and skin oils. But the idea that bathing opened a route for miasma to enter was not the same as a demonstrated account of how illness spread.
A precaution shaped by a mistaken model
Avoiding a bath could therefore feel protective, especially when cleanliness itself was debated through the medical ideas of the time. This was not a universal rule followed by everyone: beliefs and bathing habits varied, and the warning reflects one strand of medical thought rather than a single consensus.
The larger shift came as explanations of disease moved away from poisonous air and toward specific infectious agents. That change altered what washing meant: instead of making the body dangerously permeable, cleaning could help remove material that carried infection. The old fear is a reminder that a sensible-sounding precaution can follow from a wrong model of the body—and that changing the model can reverse the advice.
