please stop mixing things together ... lactose tolerance in adulthood is a DNA mutation that happened to one human some 10.000 years ago and that has been transferred genetically since then.
We are NOT talking about allergies here, lactose tolerance/intolerance has nothing to do with allergies, its all about if your body has the genes to produce the enzyme lactase after reaching adulthood.. basically everyone produces this enzyme as newborn(except some very unlucky few, as human milk contains more lactose than cows milk), its all about if the body is switching production of enzymes off or not when you reach X age.
The natural state is to be lactose intolerant, just like basically all other mamals.. that is also why you shouldn't give milk to any adult animals.