When your child has ulcerative colitis (UC), parts of their large intestine -- the rectum and colon -- become inflamed. Sores, called ulcers, form inside, which can make pus or mucus and cause bleeding. But doctors aren’t sure exactly what makes the disease start in the first place.

They do know that several things play a role in UC: a child’s genes, their immune system, the balance of bacteria in their gut (known as the microbiome), and some things in the environment.

Researchers think the process might work something like this:

  • Your child gets an infection, from bacteria or a virus, in their digestive system.
  • The immune system’s job is to fight the infection, using the natural process of inflammation.
  • For some reason, the immune system keeps fighting after the infection is gone. The inflammation doesn’t go away.

Who’s at Risk?

UC is more common in adults than children, but pediatric cases seem to be on the rise. Research suggests the number of kids younger than 10 getting UC is staying the same, but the number of those ages 11 to 15 getting the diagnosis is going up.

Genetics play a role in your child’s chances of getting UC. Their risk is higher if a close relative -- such as a parent or sibling -- has it. But most people who have the condition don’t have a family history.

Children of any race can get UC, but it happens more often in whites. For those with Ashkenazi Jewish ancestors, the odds go up. 

Young people who smoke, or who are around secondhand smoke regularly, have higher odds of getting UC or a related condition, Crohn’s disease.

Other Possible Factors

Scientists have looked into many factors that might explain why people get ulcerative colitis.

Studies into the connection between nutrition and UC haven’t come up with clear conclusions. Researchers have looked closely at fiber and fat, but it’s not clear either plays a role in causing or preventing UC.

There may be a link between higher levels of arachidonic acid, a fatty acid in meat, eggs, and poultry, and a higher risk of UC. Higher levels of another fatty acid, linoleic acid, in the diet might also make UC more likely. It’s found in seeds, nuts, vegetables oils, meat, and eggs. But scientists need to learn more about what the connection is.

Researchers looking into stress and depression also haven’t found clear evidence that mood raises someone’s chances of UC.

Once your child has UC, diet and stress may make the condition worse, however.

Because antibiotics can alter the balance of bacteria in the gut, researchers have studied whether these drugs are linked to ulcerative colitis. Although there may be a link to Crohn’s disease, studies haven’t found a tie to UC.

WebMD Medical Reference

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