Introduction Poor lactose metabolism as a result of lactase deficiency There are two forms primary hereditary ↑ frequency in african americans and asians age-dependent secondary post-gastroenteritis Presentation Symptoms bloating cramps osmotic diarrhea due to fermentation of undigestable lactose by intestinal bacteria to H2, CH4, organic acids Evaluation H2 gas detected on breath following oral lactose load Treatment Conservative eliminate dairy from diet take lactase pills when consuming dairy