While speaking to your primary care doctor
is important for specific situations, in general colon cleanses are neither safe nor recommended.
The colon is the large intestine. It is the end of the gastrointestinal system, where fluid is absorbed. It is also home to many bacteria that help breakdown undigested food. These bacteria are normal and actually help prevent more dangerous or infectious bacteria.
Historically, people thought somehow cleaning out the normal bacteria out and "toxins" from the colon would be of benefit. This dates back to the ancient Egyptians. However, as mentioned, the bacteria are actually good for your system. In addition, there are no real "toxins" in the colon--it mainly contains just undigested food material. This is naturally removed by defecation.
The colon cleanse can be performed many ways, but the most common is through the application of a cleansing solution (its contents vary) to the colon through the rectum (like an enema). This carries the risk of colon rupture or infection. There can also be dangerous fluid shifts in people with heart or kidney disease or inflammatory bowel disease
. Other types of colon cleanses including taking various laxatives--but this is again not safe.
I would not recommend a colon cleanse. There is no theoretical benefit to it. There is real harm that can occur. Talk to your primary doctor for more information.