What Is Melanosis Coli?

Medically Reviewed by Minesh Khatri, MD on February 20, 2024
4 min read

Melanosis coli is a medical condition caused by the release of a pigment molecule — called lipofuscin — into the mucus membranes of the large intestine (colon).

Melanosis coli isn’t life-threatening. Most likely, you won't even know that you have it. It’s detected through a colonoscopy and is caused by the consistent use of certain laxatives. 

There are typically no symptoms associated with melanosis coli. The most common way that it’s discovered is through a colonoscopy, a test that is used to detect polyps or other irregularities in the colon.  

Melanosis coli causes a dark brown mucosal pigmentation in the proximal colon, which refers to the beginning portion of the large intestine that connects to the small intestine and the middle regions of the large intestine. 

However, there are some reported cases where the coloration was almost black in color. 

Most patients with melanosis coli also have increased rates of polyps in their colon. Polyps are cell growths that come out of the mucus lining and are typically not harmful. It is unclear how melanosis coli is linked to this increased rate of colon polyps.

There's question as to whether increased polyps is a true symptom of melanosis coli. The increased rate of polyp detection could be due to the darker intestinal coloration that melanosis coli causes. This coloration change makes polyps easier to see in a colonoscopy.

There's some evidence of increased rates of adenomas — non-cancerous tumors — in patients with melanosis coli. In general, these are not a cause for alarm. More research is needed to determine if this condition is simply a change in coloration or a sign of deeper problems and chronic injury to the colon.

Melanosis coli is mostly caused by using some laxatives for a long amount of time. Laxatives are only meant to be used as a short-term solution to constipation. They shouldn’t become a normal part of your healthy bowel routine. 

Melanosis coli is most often seen in people ages 45 and older. But anyone who uses laxatives for more than a few months at a time may develop the condition. It’s seen equally in men and women. 

The particular kinds of laxatives that lead to melanosis coli contain sennosides, which are found in rhubarb and the senna plant. These types of over-the-counter herbal laxatives don’t become active until they have passed into the large intestine. Once active, they cause damage to the mucus lining and the cells die. This cell death creates the dark pigment that is seen in colonoscopies. Other cells in your body eventually clean up these dead cells. Osmotic or diphenolic laxatives are not associated with melanosis coli.

Although consistent laxative use is the most common cause, other causes have been seen in certain cases where no laxatives were used including: 

  • Frequently consuming herbal remedies and herbal teas that contain anthraquinone
  • Chronic colitis 
  • Chronic diarrhea 
  • Use of non-steroid anti-inflammatory drugs‌ (NSAIDs) like aspirin, ibuprofen, and naproxen

Melanosis coli isn’t linked to increased rates of colon cancer, but research is ongoing. 

In order for your doctor to give you a positive diagnosis of melanosis coli, they must do a biopsy — or removal — of the colon tissue. This is to make sure you're properly diagnosed and that they're not missing a condition that could indicate much more severe problems.

An example of this is Peutz-Jeghers Syndrome, a disorder that leads to a 15 times greater rate of colon cancer than normal. True melanosis of the colon, a related but far more serious condition, could indicate that you have this condition, so it needs to be ruled out.

The most effective treatment for melanosis coli is to simply stop taking the laxative or herbal remedy that you've been using. The darker coloration should be cleared up by one year after you’ve stopped.

To help maintain a healthy bowel without the use of laxatives, consider making a few changes to your lifestyle, including:

  • Eat a diet rich in fiber. This includes eating more fruits, vegetables, whole grains, and legumes, and eating less food that can lead to constipation. Limit or avoid foods and drinks like coffee, fried foods, alcohol, and red meat. Your doctor may also recommend oral fiber supplements if your symptoms are extreme. 
  • Increase your exercise. Regular exercise can help keep your bowel movements consistent.
  • Get good sleep. A consistent sleep schedule helps your body develop a bowel movement routine.‌