People suffering from Primary Lactose Intolerance often have no reason for the decline of their lactase production- it simply reduces over time. These people may have a dairy ‘threshold’ where they can eat a certain amount before symptoms appear. Unfortunately, even this threshold often gradually decreases.
Secondary Lactose Intolerance occurs when injury, illness or surgery interrupts the lactase production of the small intestine. The good news is that production is often restored as the body heals.