The fact is that douching can irritate the lining of your rectum and bowel and make it more susceptable to infection and injury, even if you only use plain warm water*. The lower bowel and rectum are coated with anal mucus which help to protect you and to lubricate the passing of faeces.
When you douche, you wash away this protective coating, and this means that your rectum has no barrier to protect it from injury, infection or irritation caused by the fucking.
The primary purpose of your bottom is to pass faeces from the body (really!). As you digest food and it passes through the digestive system, slowly more and more water is absorbed from the faeces by the bowel and this absorption process even continues in the rectum.Read the rest, via the Mothership Blog (UK)