What food poisoning is
Food poisoning happens after eating food or drink contaminated with germs such as Salmonella, Campylobacter, E. coli, norovirus or toxins produced by bacteria like Staphylococcus aureus or Bacillus cereus. Common sources are undercooked meat, eggs and seafood, unwashed produce, reheated rice and food left out of the fridge.
Toxins already present in food can cause vomiting within 1 to 6 hours. Bacterial infections usually start 1 to 3 days later, sometimes longer.
What a stomach bug is
A stomach bug is viral gastroenteritis, an infection of the stomach and intestines. Norovirus is the most common cause in adults and rotavirus in young unvaccinated children. It spreads easily through contact with infected people, contaminated surfaces and, sometimes, food handled by someone who is ill.
Symptoms usually start 12 to 48 hours after exposure, and outbreaks often spread through families, schools, care homes and cruise ships.
How to tell them apart
- Timing: food poisoning can start within hours of a meal; a stomach bug usually starts 1 to 2 days after contact with someone ill.
- Who gets ill: people who ate the same food fall ill around the same time with food poisoning; a stomach bug spreads from person to person over days.
- Symptoms: both cause nausea, vomiting, diarrhoea and cramps; vomiting is often prominent with norovirus and toxin-related food poisoning.
- Blood in stools and high fever: more suggestive of bacterial food poisoning.
- Duration: most stomach bugs last 1 to 3 days; bacterial food poisoning can last up to a week.
In practice, the treatment is the same for both, and stool tests are only needed in some cases.
Staying hydrated
- Take small, frequent sips of water, every few minutes, if you are vomiting.
- Oral rehydration solutions from the pharmacy replace salts and sugar in the right balance and are recommended for children, older adults and anyone at risk of dehydration.
- Sports drinks contain more sugar and fewer salts than rehydration solutions; they can help healthy adults but are not ideal for children.
- Avoid alcohol, strong coffee and very sugary fizzy drinks, which can worsen diarrhoea.
- Keep breastfeeding or giving formula to babies.
What to eat while recovering
Eat as soon as you feel able, starting with small portions of plain foods: toast, crackers, rice, pasta, bananas, potatoes, soup and plain chicken. You do not need to follow a strict diet, but fatty, spicy and very rich foods may be harder to tolerate for a few days.
See what to eat with diarrhoea, foods for nausea and bland diet foods.
Preventing spread
- Wash hands with soap and water; alcohol gels do not kill norovirus well.
- Clean surfaces and toilets with a bleach-based cleaner.
- Do not prepare food for others while ill and for 48 hours after symptoms stop.
- Stay off work or school until 48 hours after the last episode of vomiting or diarrhoea.
- Wash contaminated clothing and bedding at a high temperature.
Preventing food poisoning
- Cook meat, poultry and eggs thoroughly.
- Keep raw and cooked foods separate.
- Cool leftovers quickly and refrigerate within 2 hours; reheat until piping hot once only.
- Wash fruit and vegetables.
- Respect use-by dates.
Babies and young children
Babies and toddlers dehydrate faster than adults. Keep offering breast milk or formula, and give oral rehydration solution in small amounts, such as a teaspoon every few minutes, if they are vomiting. Fruit juice and fizzy drinks can worsen diarrhoea.
Seek medical advice promptly if a baby under 6 months has vomiting or diarrhoea, or if any child has fewer wet nappies, is unusually sleepy or floppy, has cold hands and feet, a sunken soft spot on the head, green vomit or blood in the stools. Children should stay off nursery or school until 48 hours after the last episode.
When to seek medical help
- Signs of dehydration: very little urine, dark urine, dizziness, dry mouth or sunken eyes.
- Blood in vomit or stools, or black stools.
- High fever or severe stomach pain.
- Vomiting for more than 2 days or diarrhoea for more than 7 days.
- Babies, older adults, pregnant people and those with weak immune systems should seek advice earlier.
- Confusion, a stiff neck or a rash.
Key points to remember
- Food poisoning often affects people who shared a meal; stomach bugs spread person to person.
- Both are treated with fluids, rest and bland food.
- Oral rehydration solutions are best for those at risk of dehydration.
- Dehydration, blood or prolonged symptoms need medical help.
Questions about food poisoning and stomach bugs
These answers are general information and do not replace an examination or individual medical advice.
How quickly does food poisoning start?
From 1 hour to several days after eating, depending on the cause.
How long does a stomach bug last?
Usually 1 to 3 days, sometimes a little longer.
Are electrolyte drinks good for a stomach bug?
Oral rehydration solutions are the best choice. Sports drinks can help adults but contain more sugar.
Should I eat with food poisoning?
Eat bland foods when you feel able. Fluids are more important in the first hours.
Is a stomach bug contagious?
Yes, very. Stay home until 48 hours after symptoms stop.
Do I need antibiotics for food poisoning?
Usually not. Most cases get better on their own. A doctor decides in severe cases.
Can food poisoning and a stomach bug be prevented the same way?
Good hand washing and food hygiene help prevent both, but norovirus also needs bleach-based cleaning.
Sources
This guide is for general information and does not replace medical advice. How a problem is diagnosed and treated depends on your examination and medical history. If you think you have an emergency, contact your local emergency services.