Question: What are the symptoms of Crohn’s disease?
Answer: The most common symptoms of Crohn’s disease are

diarrhea
cramping and pain in yourabdomen, or belly
weight loss

Other symptoms include

anemia
eye redness or pain
feeling tired
fever
joint pain or soreness
nausea, loss of appetite, or vomiting
skin changes such as red, tender bumps under the skin

Your symptoms may vary depending on the location and severity of your inflammation.
Question: What causes Crohn’s disease?
Answer: Doctors aren’t sure what causes Crohn’s disease. Experts think the following factors may play a role in causing Crohn’s disease.5

Abnormal immune reaction

One cause of Crohn’s disease may be an abnormal reaction of your body’s immune system, which happens when your immune system attacks bacteria that tend to live in your intestines. This immune system response causes inflammation in the digestive tract, leading to Crohn’s disease. Abnormal immune reactions can be triggered by the environment, genes, or the microbiome.

Environment

Experts think a person’s environment—the place where someone lives, the conditions in which they live, and factors outside their body—may play a role in causing Crohn’s disease. Researchers are still studying how people’s environments interact with genes, the immune system, and the microbiome to affect the chance of developing Crohn’s disease. For example, research has shown smoking may double your chance of developing Crohn’s disease.6

Genes

Crohn’s disease sometimes runs in families. Research has shown that if you have a parent or sibling with Crohn’s disease, you may be more likely to develop the disease. Experts continue to study the link between genes and Crohn’s disease.

Microbiome

The microbes in your digestive tract—including bacteria, viruses, and fungi—that help with digestion are called the microbiome. Studies have found differences between the microbiomes of people who have inflammatory bowel disease (IBD) and those who don’t. Researchers are still studying the relationship between the microbiome and IBD.