What is (are) Lactose Intolerance ?
Four types of lactase deficiency may lead to lactose intolerance:
                
- Primary lactase deficiency, also called lactase nonpersistence, is the most common type of lactase deficiency. In people with this condition, lactase production declines over time. This decline often begins at about age 2; however, the decline may begin later. Children who have lactase deficiency may not experience symptoms of lactose intolerance until late adolescence or adulthood. Researchers have discovered that some people inherit genes from their parents that may cause a primary lactase deficiency.  - Secondary lactase deficiency results from injury to the small intestine. Infection, diseases, or other problems may injure the small intestine. Treating the underlying cause usually improves the lactose tolerance.  - Developmental lactase deficiency may occur in infants born prematurely. This condition usually lasts for only a short time after they are born.  - Congenital lactase deficiency is an extremely rare disorder in which the small intestine produces little or no lactase enzyme from birth. Genes inherited from parents cause this disorder.