Why do I get stomach pain when I consume dairy products?

Dairy products-pain. Some ethnic groups, older people, & people who take antibiotics often may have a condition of "lactose intolerance", i.e., they lack (to varying degrees) the enzyme that breaks down milk sugar so it is digestible. Those who lack enzyme develop bloating, gas, diarrhea. Lactaid/dairy ease tablets provide this enzyme; also have pre-treated milk. Some ice creams are "lactose free".