How can you tell the difference between a Crohn's flare and something more serious like food poisoning, e coli or salmonella?

Culture. A stool culture will give the answer in about 48 hours. If you are under treatment for crohn's, your gastroenterologist knows all about this. The truth is that most food poisoning is self-limited though a major nuisance while you have it; the greatest concern is the e. Coli that cause hemolytic-uremic syndrome.
Stool culture needed. A crohn's flare is as serious as food poisoning, including e. Coli and salmonella. Both can course with diarrhea and fever depending on severity, yet many cases of food poisoning will course with nausea and vomiting and less likelyhood of having blood in the stool. The onset is frequently abrupt and the abdominal pain is usually more diffuse and less localized. A stool culture can be diagnostic.