There are three types of lactose intolerance: primary, secondary, and congenital.[1]
- Primary lactose intolerance is the most common. This is the normal drop in intestinal lactase production that occurs for most people between ages two and five.
- Secondary lactose intolerance is a sudden decrease in lactase production due to damage to the small intestine. This is usually a transient condition resulting from conditions like infection, celiac disease, Crohn’s disease, food allergy, or small intestinal bacterial overgrowth (SIBO).[1]
- Congenital lactase deficiency (CLD) refers to an inability to produce lactase from birth. It’s an autosomal-recessive disorder, caused by a mutation in the LCT gene, and it is extremely rare.[2]