True story... Years ago, my friend (let's call her "Alice") and I put it together that whenever we went over to "Bob's" house for dinner we both got the runs. Finally, one of us mentioned it to Bob and he immediately blamed his wife: "I've told her," he said, "sometimes she doesn't wash the soap off the plates well enough." Something like that had never occurred to me. Sheer speculation, but it made some sense, as the dinners themselves were fairly basic.