One of the intriguing aspects of the acute infectious diarrhoeas is that, while resulting from an infection of the intestinal tract, they only last from a few hours to a few days. The study of the interactions between infectious agents and intestinal epithelium has allowed a better understanding of the cellular and molecular mechanisms that cause the sudden loss of water and electrolytes, the hallmark of acute diarrhoea. These interactions have also led to formulating oral rehydration solutions used worldwide now. They do not, however, allow understanding the short course of most intestinal infections. For that, one has to consider the intestinal epithelium as part of an anatomical and functional system that, including the many types of cells present in the lamina propria, constitutes the intestinal mucosa. Infectious agents interact with the whole of the mucosa, including the cells of the lamina propria. This leads, among other things, to a change in the functions of the epithelial cells and accelerates their turnover. The pathophysiology of the intestinal mucosa leads to better understand the short and benign course of most intestinal infections. It also leads to better understand the physiology of the intestinal mucosa, and the interactions between the body and its nutritional environment.