Colon therapy refers to flushing water through the entire length of the colon or large intestine. It is also called colon hydrotherapy or colonic irrigation.

Colon therapy is performed in order to eliminate wastes that have accumulated in the colon and to promote a better-functioning large intestine. It is believed that colon therapy can relieve a score of symptoms from gas, bloating, and constipation to depression, insomnia, and headaches. Colon therapy also is used to administer therapeutic substances via the mucous membranes of the colon.

Colon therapy is not recommended for people suffering from heart or kidney disease, cancer, or diseases of the colon, including diverticulitis, Crohn's disease, or ulcerative colitis. A colon therapist should always use disposable tubing to reduce the risk of infection.

Colon therapy is usually administered by a trained colon hydrotherapist or colon hygiene technician in a clinic or spa. The procedure takes about one hour. The patient lies on their back and the therapist inserts a plastic tube into the anus. Either plain filtered water or water to which herbs, enzymes, oxygen, or other therapeutic agents are added is pumped into the rectum either by relying on gravity or by a mechanical device. The water is kept at body temperature. During a session, a total of 20-35 gallons of water can be flushed through the entire length of the colon through a process of filling and releasing. Sometimes, the water is held inside the colon for a designated period of time while the therapist massages the abdomen to enhance waste removal. Waste is then eliminated. Sometimes it is necessary to undergo several colon therapy sessions for a complete colon cleansing.

There have been reports of significant and sometimes fatal water and salt imbalances resulting from colon therapy. In these cases, people became weak, developed fluid in their lungs, suffered convulsions, and died. Combining fasting with colon therapy may increase the risk of a dangerous fluid imbalance. With improper technique, the tubes could tear the colon. If equipment is not properly sterilized, bacterial contamination can result in infection.

Relief from constipation may result. Many clients treated claim their headaches, arthritis, and other aches and pains were banished.