Food Poisoning
Also known as Foodborne illness, Gastroenteritis
This article is general health information for the selected condition. It is not a diagnosis and does not replace clinical judgement. If you have questions or need treatment advice, please consult a qualified healthcare professional.
What is food poisoning?
Food poisoning is illness caused by eating food contaminated with bacteria, viruses, parasites or their toxins. Most cases resolve within a few days with fluids alone. The main risk is dehydration, particularly in young children and older adults, and certain warning features require urgent assessment.
Causes
- Bacteria such as Salmonella, Campylobacter and E coli
- Norovirus, the most common viral cause
- Preformed toxins from Staphylococcus aureus or Bacillus cereus
- Parasites including Giardia
- Cross contamination or inadequate cooking and storage
Symptoms
- Nausea and vomiting
- Diarrhoea, sometimes with blood
- Abdominal cramps
- Fever
- Headache and muscle aches
- Signs of dehydration including thirst and reduced urination
Risk factors
- Age under 5 or over 65
- Pregnancy
- Weakened immune system
- Reduced stomach acid from acid suppressing medicines
- Travel to areas with unsafe water
Diagnosis
- History of food exposure and incubation timing
- Assessment of hydration status
- Stool culture or PCR panel when severe or prolonged
- Blood tests for kidney function and electrolytes if unwell
- Notification to public health for certain organisms
Treatment
- Oral rehydration solution as the mainstay
- Small frequent sips if vomiting
- Gradual return to normal diet as tolerated
- Intravenous fluids when dehydration is significant
- Antibiotics only for specific organisms or severe illness
- Avoiding antidiarrhoeal medicines when there is bloody diarrhoea or fever
Self care
- Rehydrate with oral rehydration solution in small frequent sips
- Rest and return to plain food when appetite allows
- Continue breastfeeding or formula for infants
- Wash hands thoroughly with soap after using the toilet
- Stay off work or school until 48 hours after symptoms stop
- Avoid antidiarrhoeal medicines if there is blood or fever
When to see a doctor
Book an appointment if:
- Symptoms lasting more than three days
- Unable to keep fluids down
- Blood in the stool
- High fever
- Recent travel abroad
- Pregnancy, or someone very young, older or immunosuppressed
Some symptoms need emergency care rather than an appointment. See the warning signs listed above.
Prevention
- Cook food thoroughly, especially poultry and mince
- Keep raw and cooked foods separate
- Chill leftovers promptly and reheat thoroughly
- Wash hands before preparing food
- Avoid unpasteurised milk and untreated water
- Take extra care in pregnancy and with reduced immunity
Outlook
Most food poisoning resolves within a few days with fluids alone and causes no lasting harm. Some organisms cause longer illness, and a minority of people develop post infectious irritable bowel syndrome. Serious complications such as kidney injury from certain E coli strains are uncommon but are the reason bloody diarrhoea warrants assessment.
Common questions
When should I seek medical help?
Seek care for blood in the stool, a high fever, signs of dehydration such as very little urine or dizziness on standing, symptoms lasting beyond three days, or severe abdominal pain. Infants, older adults and pregnant people should be assessed earlier.
Should I take medicine to stop diarrhoea?
Not if there is bloody diarrhoea or high fever, because slowing the gut can prolong some bacterial infections and increase complications. For simple watery diarrhoea, short term use is usually acceptable in adults.
How soon after eating do symptoms appear?
It varies by cause. Toxin mediated illness can begin within one to six hours, whereas Salmonella and Campylobacter typically take one to three days, so the most recent meal is not always responsible.
References
Important: Dard AI is not a medical device and does not diagnose, treat, or replace clinician judgement. This article is general information only. Always consult a qualified healthcare professional about diagnosis and treatment, and seek emergency care for severe or rapidly worsening symptoms.