What does this say about the flour?

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The message in the box says: "Do Not Eat or Play with Raw Flour, Dough or Batter" and then goes on about washing your hand or something like that.  Why would the mill make you treat their flour like a biohazard material?  Have never seen it before.  Thanks, h. 

I see that on 5 pound retail bags of flour too,

Many people just don't realize raw grain, and the flour that comes from it, is not perfectly hygienic.  Granaries have all sorts of insects and field mice running all over the product.

It's not like they wash every kernal of grain before milling it.

Raw flour can actually be contaminated with a lot of nasty stuff. There was a big salmonella outbreak a while ago that was traced back to commercial raw cookie dough, but the source of contamination was not any egg or dairy product, it was the raw flour. So nowadays if you ever want to make homemade cookie dough most recipes call for you to roast the flour before hand.