What is the primary symptom of both Crohn's disease and lactose intolerance?

The primary symptom shared by both Crohn's disease and lactose intolerance is diarrhea. In Crohn's disease, which is a form of inflammatory bowel disease (IBD), diarrhea occurs due to inflammation in the gastrointestinal tract, affecting the ability to absorb nutrients and resulting in watery stools. This symptom can be chronic, leading to significant discomfort and potential dehydration.

In the case of lactose intolerance, diarrhea arises when lactose, a sugar found in milk and dairy products, is not properly digested due to a deficiency in lactase, the enzyme responsible for breaking down lactose. The undigested lactose causes an osmotic effect in the intestines, pulling in water and leading to loose stools.

Thus, diarrhea is a significant overlap symptom in both conditions, highlighting the disturbances in the digestive system's normal function.