During a colonic, warm water is slowly introduced into your large intestine through a small tube inserted into the rectum. The water fills the colon, softens and loosens built-up waste, and then the waste flows back out through the same tube or a separate drainage basin. A typical session uses about 8 gallons of water over 30 to 40 minutes, with multiple cycles of filling and releasing.
What Happens During a Session
You lie on a padded table, usually on your back or side, while a therapist inserts a small, lubricated tube a few inches into the rectum. Filtered water, heated to between 99 and 103 degrees Fahrenheit, flows into the colon in controlled amounts. As the water enters, it gently stretches the colon wall, which triggers the muscles of the intestine to contract. These contractions, the same wave-like movements your colon uses during a normal bowel movement, push the loosened waste material back out.
The therapist controls the flow, pausing to let the colon fill, then releasing the water and waste before repeating the cycle. Most sessions involve several of these fill-and-release rounds. Some practitioners also gently massage the abdomen to help move things along.
Open Systems vs. Closed Systems
There are two main types of equipment, and the experience differs between them.
- Open systems use gravity to move water into the colon at low pressure. You sit or recline on a table with a built-in basin. The waste exits around the tube and drains into the basin below you, similar to a toilet. You’re typically alone in the room for most of the process.
- Closed systems use a pressurized stream of water delivered through an attached hose. The waste travels back out through the same tube into a sealed system, which means less odor and noise. A therapist stays with you to manually control the filling and draining cycles.
Open systems are generally considered gentler because they rely on gravity rather than mechanical pressure. Closed systems give the therapist more control over water volume and timing.
How to Prepare Beforehand
Full fasting isn’t necessary, but most practitioners recommend eating lightly for the 48 hours leading up to your appointment. That means cooked vegetables, simple soups, steamed fish, soft grains like oatmeal or white rice, and ripe fruits. The goal is to reduce the amount of undigested residue sitting in the colon during the session.
In the 24 hours before, you’d simplify further: vegetable broth, smoothies, soft-cooked vegetables, smaller portions overall. Avoid fried foods, heavy dairy, red meat, sugary desserts, and alcohol for at least two days prior. Small amounts of coffee the day before are generally fine, but skip it the morning of your appointment. On the day itself, many people do best with just herbal tea, water, or a small smoothie before arriving.
What It Does to Your Gut Bacteria
Flushing the colon with water doesn’t just remove waste. It also washes out a significant portion of the bacteria living there. Research on bowel cleansing has found that a single lavage can reduce the total microbial population by roughly 31-fold. In about 22% of people studied, the bacterial community was disrupted enough that it temporarily lost its unique, individual composition.
The good news is that bacterial levels and community structure were largely restored within 14 days. But the recovery wasn’t uniform. People who received a more aggressive single-dose cleansing actually saw a more pronounced shift in their bacterial makeup afterward, with increases in certain bacterial groups that aren’t typically dominant in a healthy colon. This suggests that repeated or frequent colonics could create ongoing disruption to your gut ecosystem, even if each individual session seems temporary.
What the Evidence Says About “Detox”
The central claim behind colonics is that they remove toxins from the body and promote general health. A systematic review of the published medical literature found no methodologically rigorous controlled trials to support this. The researchers looked across both conventional and alternative medicine sources and concluded that the data supporting colon cleansing for detoxification or general health promotion simply doesn’t exist in any reliable form.
There is some early-stage research into colonics for specific conditions. A pilot study on people with irritable bowel syndrome found potential benefit, with researchers speculating that irrigation might wash out certain metabolic byproducts that contribute to gut sensitivity. But even those investigators acknowledged the exact mechanism is unknown, and the study was small.
Your colon already has a built-in waste removal system. The liver and kidneys handle the body’s actual detoxification work. The colon’s job is to absorb water and electrolytes from digested food and move solid waste toward elimination, which it does continuously without assistance in most people.
Risks and Who Should Avoid Them
Serious complications are rare but real. Bowel perforation, where the colon wall tears, is the most dangerous risk. Estimates for perforation from transanal irrigation procedures sit at roughly 20 per 1 million procedures. The risk increases when internal pressure climbs too high. Research has shown that perforation can occur at pressures between 50 and 109 mmHg, which is why gravity-fed systems with naturally lower pressure are considered safer than pressurized delivery.
Beyond perforation, the more common concerns are electrolyte imbalances from repeated sessions. Your colon actively absorbs sodium, potassium, and other minerals. Flushing it repeatedly can interfere with that process, potentially causing symptoms like cramping, nausea, or dizziness. Infections from improperly sterilized equipment, though uncommon at licensed facilities, have also been documented in case reports.
Colonics are contraindicated for several medical conditions: pregnancy, acute diverticulitis, active inflammatory bowel disease (Crohn’s disease or ulcerative colitis), recent abdominal or bowel surgery, recent radiation therapy to the abdomen, severe heart disease, liver cirrhosis, kidney failure, and acute anal conditions like hemorrhoids or fissures that would prevent tube insertion.