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How Fast Does Food Poisoning Happen, Really?

Yes, it’s possible to feel sick before you’ve even left the restaurant

Maybe you’ve treated yourself to a nice meal out, or you decide to keep it healthy and have a fresh salad for lunch, and then some hours later you’re left incapacitated on your bathroom floor contemplating every substance you’ve ever ingested. Where did it all go wrong? Was it the romaine lettuce you ate six hours ago? The oysters you ate two days ago? How quickly — or slowly — does food poisoning set in?

Depending on what exactly it is causing your food poisoning, the time it takes for symptoms to set in can vary widely. In some cases, you could start feeling ill before even finishing your meal. In rare outbreaks of foodborne Listeria, it can take up to a month. Most commonly, though, symptoms will set in within 6 to 48 hours. The exact timing depends on a number of factors, including age and medical conditions, but the biggest factor will be what exactly is causing the food poisoning itself.

According to the Centers for Disease Control, the top five germs responsible for food poisoning are norovirus, Salmonella, Clostridium perfringens, Campylobacter and Staphylococcus aureus. Each has its own common origins, as well as its own timeframes for the onset of symptoms. Among the five, norovirus is most common, as it’s spread from person to person in addition to being found on contaminated leafy greens, shellfish and fruits. Symptoms of nausea, vomiting and diarrhea typically occur within 12 to 48 hours. 

Of the other four, Staphylococcus aureus has similarly human origins. Typically, it occurs when staph bacteria from a person’s hands is transferred onto food someone else consumes. As such, it’s often the result of food-handling practices in restaurants and other non-domestic cooking environments. With staph, symptoms can set in as soon as 30 minutes after eating, but it could take up to eight hours. 

Salmonella, Clostridium perfringens and Campylobacter, meanwhile, are all predominantly meat and dairy based. Poultry is a common culprit among the three, particularly when raw or undercooked. Unpasteurized milk, eggs, raw produce, large beef roasts, gravies and contaminated water can also cause them. Symptoms will set in between six hours and six days, depending on the bacteria. The symptoms themselves will vary, too: Clostridium perfringens typically includes diarrhea and stomach cramps, but not fever or vomiting, while Campylobacter can include bloody diarrhea. 

Though most cases of food poisoning can involve a day or two of pure hell, they don’t typically require actual treatment. That said, some symptoms, such as blood in your stool in the case of Campylobacter, high fever, dehydration or symptoms that last more than three days are cause to get medical attention. 

In any case, if you start feeling gross pretty quickly after eating those week-old leftovers in your fridge, it might not totally be in your head. By the same token, you can still become sick several days after you think you might be in the clear. Save for washing your hands, hoping everyone else does the same and avoiding raw and unpasteurized foods, there’s not much we can do to actually avoid food poisoning. Just cling to that toilet bowl when it arrives and hope for the best.