Leaky gut syndrome is a proposed condition of an altered or damaged bowel lining. The term is used by some alternative medicine practitioners, but the syndrome is not a recognized diagnosis. It is hypothesized to be caused by increased permeability of the gut wall resulting from toxins, poor diet, parasites, infection, or medications. The leaky gut then allows substances such as toxins, microbes, undigested food, waste, or larger than normal macromolecules to leak through an abnormally permeable gut wall. Proponents propose that these out-of-place substances affect the body directly or initiate an immune reaction.