Soon after eating a kale salad, your stomach churns and you need to run to the nearest bathroom. There must have been something in the salad to make you sick—right?
Probably not. While a few gut-unfriendly pathogens make their presence known immediately, the most common culprits in the United States—e. coli, salmonella, norovirus and campylobacter—lurk in your bowels for several hours or days before the symptoms of food poisoning appear.
It takes time for the invaders to multiply in your intestines before you experience the telltale nausea, diarrhea and vomiting, explained Denise Monack, Ph.D., a professor of microbiology and immunology.
“If several people eat the same contaminated food,” Monack said, “some may get sick; some may not. And those who get sick will start to feel the effects at different times—a day later, or several days later.”
It depends on a variety of factors, she said, individual gut microbiomes, what other foods people ate, how much of the pathogen they consumed and the strength of their immune systems.
The upshot: If you suspect food poisoning, you’re unlikely to know the cause. The turkey sandwich you chowed down at a deli last week could be the guilty party just as easily as the fruit smoothie you made for breakfast yesterday.