Can be hazardous to your health. I was in Newport, Rhode Island, and had some seafood at an ostensibly nice restaurant. Five hours later I was quite violently ill. After finishing dinner, I felt fine, even got in a short workout and soaked in the hotel hot tub before going to bed. I woke up 2.5 hours later, and didn't sleep much after that with many trips to the bathroom.
The details are not for the faint of heart, so I'll gloss over... While lying in pain, between cursing about having to get up and bolt for the bathroom for one thing or another, I was in awe of our bodies' ability to deal with such a problem. I ate something bad for me, and when it got into my blood stream and my immune system mobilized, the first thing it did was evacuate everything from my entire digestive tract. Not pleasant, and the fact that it persisted for a couple days possibly a bit overkill, but terribly effective never-the-less.
Then there are the other side effects that followed. Namely fever and a runny nose. The fever is an easy but still pretty neat indication that things are working properly. Immune system activity burns calories, and the wasted portion is heat. Also, many bacteria have a temperature window at which they thrive, and even a few degrees elevation can slow them up enough to make clean-up easier (just think how sluggish you feel when it's 90F and 90% humidity out). The runny nose, in this case is a defense mechanism. With the body fighting off one intruder, it ups the defense to keep another from getting in.
All told the body is a pretty amazing feat of evolution.