Food poisoning: how long it lasts, what helps, and when to worry
Last updated September 3, 2026.
Food poisoning is misery with a timeline: most cases hit within hours to days of the contaminated food and resolve on their own within a week. The culprits are viruses (norovirus is the most common), bacteria (Campylobacter, Salmonella, E. coli, Staphylococcus), and their toxins, picked up from undercooked meat and poultry, unwashed produce, poor hand hygiene, or food held at warm temperatures. The treatment for nearly all of it is not medication; it is fluid, salt, and patience.
What does it look like, and how fast?
The incubation period hints at the cause. Vomiting within 1-6 hours of eating points to pre-formed toxins (Staphylococcus from creamy foods left out, Bacillus cereus from reheated rice). Nausea, vomiting, and watery diarrhea starting 12-48 hours after exposure fits norovirus. Fever with cramping and sometimes bloody diarrhea over 1-5 days suggests Campylobacter, Salmonella, or Shigella. The core symptoms are shared: nausea, vomiting, watery diarrhea, stomach cramps, aching, and a mild fever. Most cases peak within 1-2 days and resolve in under a week, though the gut can stay touchy for days after.
Who gets sick enough to matter?
Most healthy adults ride it out at home. The groups where food poisoning escalates: adults over 65, pregnant women (Listeria from soft cheeses, deli meats, and pates can cause miscarriage and is why those foods are restricted in pregnancy), babies and young children (dehydration arrives fast), and anyone with weakened immunity. Dehydration is the main danger across the board, and its signs are a dry mouth, dark and scanty urine, dizziness on standing, and in children, few wet diapers, no tears, and unusual drowsiness.
What actually helps?
- Rehydrate deliberately: small, frequent sips of oral rehydration solution (pharmacy sachets, or 6 teaspoons of sugar and half a teaspoon of salt per liter of water). Gulping large volumes triggers vomiting; sipping survives it.
- Eat when you feel like it: no need to starve or to force food. Start with bland, easy items (toast, rice, bananas, soup) and rebuild normally over a few days. Dairy can be temporarily hard to digest.
- Skip anti-diarrhea medicine in the bloody or feverish case: loperamide is fine for mild watery diarrhea in adults but is avoided when there is blood or high fever, and never in young children.
- Antibiotics are the exception: most food poisoning is viral or self-limiting; antibiotics help only specific bacterial causes and specific patients, and can harm in E. coli O157.
- Stop the spread: wash hands after the toilet and before food, do not prepare food for others, and stay off work or school until 48 hours after the last vomiting or diarrhea episode.
When is it an emergency?
Emergency care for: signs of serious dehydration (confusion, fainting, racing heart, very little urine), blood in the vomit or stool, severe constant abdominal pain, a fever above 39C (102.2F), or green vomit. Same-day assessment for the vulnerable groups, symptoms lasting beyond a week, or recent foreign travel with severe symptoms. Two rare patterns need immediate 911-style urgency: progressive weakness, blurred vision, and difficulty swallowing after canned or preserved food (botulism), and severe vomiting with chest pain (a different emergency entirely). Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
How long does food poisoning last?
Most cases resolve in 1-7 days, with the worst over in the first 48 hours. The timeline depends on the cause: toxin-mediated vomiting (Staphylococcus, Bacillus cereus) often burns out within 24 hours; norovirus typically runs 1-3 days; Salmonella and Campylobacter can stretch toward a week. A gut that stays sensitive for a few extra days is normal healing, not ongoing infection. Diarrhea persisting beyond a week, or any blood, deserves assessment and a stool test.
How do I know which food caused it?
Usually you do not, and the last thing you ate is often wrongly blamed. Incubation windows vary from 1 hour (toxins) to several days (Campylobacter, E. coli) or even weeks (Listeria), so the culprit may be several meals back. Clues: others who shared a specific meal getting sick together, high-risk foods (undercooked poultry, unpasteurized products, buffet food held warm), and timing patterns. Unless it is a formal outbreak investigation, identifying the exact food changes nothing about treatment.
Should I take anti-diarrhea medicine?
For mild watery diarrhea in an otherwise healthy adult who needs to function, loperamide is reasonable. The rules where it is not: blood or mucus in the stool, high fever, severe abdominal pain, children (especially under 12), and suspected E. coli O157, where slowing the gut is linked to complications. Bismuth subsalicylate is a gentler alternative for adults. When in doubt, let it flow; the diarrhea is the body expelling the problem.
When can I go back to work or send my child to school?
The standard public health rule: 48 hours after the last episode of vomiting or diarrhea. Earlier returns seed outbreaks, particularly in food handling, healthcare, and schools. Food handlers and healthcare workers may have stricter return rules and should check occupational policy. You are most contagious while symptomatic and for those first 48 hours after, which is exactly when people feel well enough to return and infect the break room.
Can I prevent food poisoning when cooking?
The core four: clean (wash hands and surfaces), separate (raw meat away from ready-to-eat food, its own board), cook (poultry through with no pink, use a thermometer at 74C/165F for poultry), and chill (refrigerate within 2 hours, sooner in hot weather; keep the fridge at or below 4C/39F). The classic mistakes: washing raw chicken (it sprays bacteria around the sink), reheating rice that sat out (Bacillus cereus toxin survives reheating), and thawing meat on the counter.
Is it food poisoning or a stomach bug going around?
Often indistinguishable, and the management is the same either way. Norovirus, the most common cause of 'stomach flu', spreads person to person and through food both, so the distinction is blurry at home. Food poisoning is the better guess when everyone who ate a particular meal fell ill together, while a household falling ill in sequence over days suggests person-to-person spread. Neither changes treatment: fluids, rest, hygiene, and the 48-hour rule.