The continuing ability of adults to produce lactase enzyme could, in many cases, simply be due to a physiological adaptation in some members of populations that rely heavily on dairy products, a sort of I-use-it-so-I-don't-lose-it situation. Mutations for lactase persistence probably arose several times in different places. By the way, the best mature cheddars contain next to no lactose, so enjoy fart-free! Senoufou, lactose intolerance is confined to the gut only. Having lactose-rich milk in your mammary glands can't get you! Lactose intolerance isn't an allergy, by the way.