In simple words: Lactose intolerance means your body has trouble digesting the natural sugar found in milk and dairy products. This happens when your gut doesn't make enough of a special helper called lactase, which is needed to break down that sugar. As a result, eating dairy can cause uncomfortable symptoms like gas, bloating, stomach cramps, and diarrhea.

Lactose intolerance is the body's inability to digest lactose, a type of sugar primarily found in dairy products. This arises from an insufficient production of lactase, the enzyme responsible for breaking down lactose in the small intestine. Undigested lactose passes into the colon, leading to fermentation by bacteria and causing symptoms like gas, bloating, diarrhea, nausea, and abdominal pain. Lactose intolerance can be either congenital (primary) or acquired (secondary) due to factors such as advancing age, prematurity, intestinal diseases (e.g. Crohn's disease), infections, and some cancer treatments.

Example 1: A 25-year-old female experiences bloating, cramping, and diarrhea after consuming a milkshake. She has a history of similar symptoms after eating ice cream or cheese. A hydrogen breath test confirms lactose intolerance., A 40-year-old male with Crohn’s disease develops abdominal pain and loose stools after drinking milk. Lactose intolerance is suspected as a consequence of his underlying condition., A premature infant experiences digestive upset and failure to thrive while being formula-fed. Investigations reveal congenital lactase deficiency.

Symptoms (e.g., bloating, diarrhea, gas) following consumption of lactose-containing products. Diagnostic testing such as a hydrogen breath test or lactose tolerance test can confirm the diagnosis.