The first sign of trouble as I went to bed last night was a disconcerting rumble in my stomach. I was soon overcome by nausea, intestinal difficulties and a cold sweat. My tear ducts emitted what felt like crushed ice. That symptom actually felt wonderful. My body was determined to expel a poison. But what? Only when I reviewed the ingredients of the dinner I'd prepared hours earlier did I settle on the culprit. I remembered that I'd tossed in a perishable item that had once gone a night without refrigeration. It's gone now.