Wellness Health & Well-being Sadly, Here's Another Reason Not to Eat Cookie Dough By Katherine Martinko Senior Writer University of Toronto Katherine Martinko is a writer and expert in sustainable living. She holds a degree in English Literature and History from the University of Toronto. our editorial process Twitter Twitter Katherine Martinko Updated October 11, 2018 CC BY 2.0. Marco Verch Share Twitter Pinterest Email Wellness Health & Well-being Clean Beauty First it was raw eggs, now it's raw flour. My task this evening is to bake 7 dozen thimble cookies for a Christmas cookie exchange I'm attending this weekend. It'll take a while, mixing the dough, shaping little balls, rolling in shredded coconut, poking a hole in the middle, filling the baked cookies with a spoonful of homemade jam. But the end result is so worth it -- a decadent, buttery cookie that melts in the mouth with pleasing crunch and sweetness. Thimble cookies (a.k.a. thumbprint cookies) are my Christmas staple, requested by family and friends year after year. But now, I've discovered a disturbing fact. Because the dough contains flour, I can no longer munch happily on it as I'm shaping. (I used to do this because the dough has no raw egg in it. It only comes into contact with egg when it's rolled in beaten whites to make the coconut stick.) Apparently, raw flour can contain E.coli bacteria and should not be ingested until heated. A new study, published in the New England Journal of Medicine, tells the story of an investigation that took place during the summer of 2016, when an E.coli outbreak affected 63 people in 24 states and put 17 in the hospital. Everyone recovered, but the researchers discovered that all of the outbreak strains were related. "This close genetic relationship means that people in this outbreak were more likely to share a common source of infection." It became an exercise in detective work. Everyone who got sick said that someone in their family had used flour within the week prior to infection, and tasting raw baking dough was a common factor. At first it was thought to be chocolate chips, but people had used different brands. Three ill children reported playing with play dough or eating raw tortillas at a restaurant. Eventually, the evidence pointed to flour, milled at the same General Mills facility in Kansas City, Missouri. This discovery is at odds with most people's perception of where E.coli resides. Usually it's thought to live in wet environments, like ground beef, raw chicken, even leafy vegetables; but now we know it can survive in an arid environment. The New York Times quotes Dr. Marguerite Neill, a professor of medicine at Brown University and an expert on food-borne pathogens: "It’s a new view of flour. It would have seemed incredible that this dry, powdery substance, stored on a shelf for months, could have a live micro-organism that didn’t spoil the flour but still could make someone sick." All this is to say, I'll wait to taste my delicious thimble cookies until they're thoroughly baked.