eMedicine - Lactose Intolerance : Article by Praveen K Roy, MD
"Lactase deficiency may be classified as primary, secondary, congenital, and developmental. The classification is important as it relates to diagnosis, prognosis, and treatment...
Lactose intolerance occurs in about 25% of people in Europe; 50-80% of people of Hispanic origin, people from south India, black people, and Ashkenazi Jews; and almost 100% of people in Asia and American Indians.1 Lactose is a disaccharide sugar that is found exclusively in mammalian milk and is digested by the enzyme lactase in the mucosal brush border of the intestine. Reduced intestinal lactase results in malabsorption of lactose. The unabsorbed lactose is metabolised by colonic bacteria to produce gas and short chain fatty acids, causing the clinical syndrome of abdominal cramps, bloating, diarrhoea, and flatulence."
As iI apparently have suffered with dairy intolerance since being born I guess I must have Congenital lactose intolerance
Congenital lactose intolerance is inherited as an autosomal recessive trait and is very rare.
Primary lactose intolerance is due to low levels of lactase, which develop after childhood
Secondary, or acquired, lactase deficiency may develop in a person with a healthy small intestine during episodes of acute illness. This occurs because of mucosal damage or from medications. Some causes of secondary lactase deficiency are as follows: