Have to love the stupid responses to a serious question. I use bread or crackers to try to absorb some of the lactose, after the fact. And drink some peppermint tea. It settles the stomach. Which was the initial question. Not how to prevent it, but how to deal with it, if lactose is ingested accidentally.
Thanks Rick for the sensible answer. I use the following recipe to sooth the intestinal track. It also adds some nutrients (smells nice too): 1 1/2c Jasmine rice, 2 3/4c water, 1 Lg or 2 reg chicken bouillon cubes (Knorr is good), 1 rounded Tbsp Caraway Seed, 5-6 turns freshly ground White Pepper (or 1/8tsp), 1Tbsp Omega 3 or Olive Oil). Combine all in heavy-bottomed pan, cover n bring to a boil. Boil 1-2 min. Stir a few times to prevent sticking n recover. Turn heat down to the lowest possible setting-simmer 15 min. Remove cover n fluff w/a fork. Start w/ 1/2c n see how it goes. I find if I eat this, lie down or nap for 20 min-1/2 hour n make sure to get enough fluids, I feel better within a couple of hours. Good luck – I hope this helps.