Lactose maldigestion, also known as lactose intolerance, or – incorrectly - as lactose allergy occurs when the digestive system does not produce enough of the lactase enzyme to break down complex lactose sugars into simpler sugars. The lactose sugar ferments in the small intestine, producing gas, bloating, cramps, and diarrhoea.
Note that lactose maldigesters usually tolerate lactose in small doses, but are overwhelmed by larger quantities. Also note that it is possible to pre-treat milk with the lactase enzyme and supplement the body's natural lactase enzyme with lactase pills.
Lactose maldigestion can easily be diagnosed by a test known as the breath hydrogen level test (BHL).
Common ingredients to avoid include: milk, skim milk, powdered milk, lactic acid.