"Practically all types of faecal bacterial groups participate in the invasion of the mucosa when the barrier integrity is lost. It appears that the restitution of the intact mucus barrier is the only possibility to stop an inflammation in progress, to restore the immunological equilibrium and to maintain intestinal health."
Gut. 2007 Mar; 56(3): 343-350.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1856798/
Comparative study of the intestinal mucus barrier in normal and inflamed colon
"The human gut is the natural habitat for a large and dynamic bacterial community. Recently developed molecular biology tools suggest that a substantial part of these bacterial populations are still to be described. However, the relevance and impact of resident bacteria on host's physiology and pathology is well documented. Major functions of the gut microflora include metabolic activities that result in salvage of energy and absorbable nutrients, protection of the colonized host against invasion by alien microbes, and important trophic effects on intestinal epithelia and on immune structure and function. Gut bacteria play an essential role in the development and homeostasis of the immune system. It is important to underscore that the specialised lymphoid follicles of the gut mucosa are the major sites for induction and regulation of the immune system. On the other hand, there is evidence implicating the gut flora in certain pathological conditions, including multisystem organ failure, colon cancer and inflammatory bowel diseases."
Digestion. 2006; 73 Suppl 1: 5-12.
https://www.ncbi.nlm.nih.gov/pubmed/16498248
Enteric flora in health and disease.
"The most commonly used commercial enema formulations rely on their hyperosmolarity to thoroughly cleanse the rectal vault. We have shown that a hyperosmolar sexual lubricant gel causes significant loss of single columnar epithelium minutes after a single dose; this loss was not observed when an isoosmolar lubricant was used. Other studies have also reported mucosal damage due to hyperosmolar solutions, though the osmolality is only indirectly implicated by association. A large proportion of users simply use tap water (a hypoosmolar formulation) due to easy availability; however, epithelial loss has also been reported after its use."
AIDS Research and Human Retroviruses. 2013 Nov; 29(11): 1487-1495.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3809953/
"There is a dearth of data on the frequency as well as types (aqueous-, oil-, silicone-based or numbing) or specific brands of lubricants used in populations practicing AI [anal intercourse]. Safety data is limited because lubricant products are classified in the US as “medical devices” and in Canada as “cosmetics”, thereby avoiding the safety testing that accompanies drug licensure."
Sexually Transmitted Diseases. 2012 January; 39(1): 59-64. (Author manuscript)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3244680/