Food Poisoning
Symptoms, Causes & Treatment
Food poisoning affects around 2.4 million people in the UK each year. Most cases are mild and self-limiting, resolving within 1–3 days with oral rehydration. Some pathogens cause serious illness requiring urgent medical care, particularly in vulnerable groups.
What is Food Poisoning?
Food poisoning is illness caused by consuming food or drink contaminated with bacteria, viruses, parasites, or their toxins. The most common causes in the UK are norovirus, Campylobacter, Salmonella, and E. coli. Onset ranges from 1 hour (toxin-mediated) to 72 hours (bacterial infection) after ingestion. Most cases resolve without specific treatment, but severe cases — particularly in the elderly, pregnant, immunocompromised, or infants — require medical attention.
Symptoms of Food Poisoning
Food poisoning typically causes rapid-onset nausea, vomiting, diarrhoea, and abdominal cramps. The onset time and specific symptoms help identify the causative pathogen.
Sudden onset nausea and vomiting · Diarrhoea · Abdominal cramps · Fever · Headache and muscle aches · Symptoms begin 1–72 hours after eating contaminated food · Multiple people affected after eating the same meal
Signs of severe dehydration: dry mouth, no urine output, sunken eyes, confusion · Bloody diarrhoea (possible E. coli O157 or Campylobacter — HUS risk) · High fever above 38.5°C · Symptoms not improving after 72 hours · Vulnerable groups: elderly, infants, immunocompromised
Bloody diarrhoea · High fever above 38.5°C · Severe dehydration (no urine, dry mouth, confusion) · Symptoms not improving after 72 hours · Elderly, pregnant, or immunocompromised — seek urgent medical care.
What Causes Food Poisoning?
Food poisoning is caused by ingestion of food or drink contaminated with pathogens or toxins. The specific pathogen determines the onset, duration, and severity of illness.
Salmonella, Campylobacter, norovirus, E. coli O157, Listeria, Shigella, and Staphylococcal toxin are the most common causes of food poisoning in the UK. Onset, duration, and character of symptoms vary by pathogen.
Food poisoning is transmitted by undercooked poultry, raw eggs, unpasteurised dairy, raw shellfish, contaminated water, and cross-contamination during food preparation. The '4 Cs' of food safety (clean, cool, cook, cross-contamination) prevent most cases.
Haemolytic uraemic syndrome (HUS) is a life-threatening complication of E. coli O157 infection, causing haemolytic anaemia, thrombocytopaenia, and acute kidney injury. Bloody diarrhoea in a child or elderly person requires urgent assessment and culture.
Traveller’s diarrhoea affects up to 40% of international travellers, most commonly from enterotoxigenic E. coli (ETEC). Prevention includes hand hygiene, safe food and water, and prophylactic bismuth subsalicylate. Treatment with azithromycin or ciprofloxacin shortens illness.
Clostridioides difficile (C. diff) causes antibiotic-associated diarrhoea, often profuse and watery with abdominal cramps. Risk is highest after broad-spectrum antibiotic use. Treated with fidaxomicin or vancomycin. Avoid anti-motility agents.
Infective gastroenteritis from norovirus, rotavirus, Campylobacter, Salmonella, Clostridioides difficile, or E. coli causes acute watery or bloody diarrhoea with cramping. Most resolve within 5–7 days. C. difficile requires specific antibiotic treatment.
Key Risk Factors
Diagnosing Food Poisoning
Most food poisoning is diagnosed clinically. Stool culture is only needed for bloody diarrhoea, severe symptoms, travel history, or suspected C. difficile. Blood tests assess severity and complications.
Treatment for Food Poisoning
Oral rehydration is the foundation of food poisoning management. Antibiotics are reserved for severe bacterial infections or specific high-risk pathogens.
Supportive Measures
Oral rehydration salts (Dioralyte) — 200ml after each loose stool. Small frequent sips of cold water. Rest. Bland diet when tolerated (crackers, rice, toast). Avoid dairy, fatty foods, and alcohol. Do not use Imodium if you have bloody diarrhoea or fever.
Post-Infective IBS & Long-Term Complications
Post-infective IBS develops in 5–10% of people after bacterial gastroenteritis. Probiotic use during and after infection may reduce risk. Symptoms lasting beyond 3 weeks, bloody diarrhoea, or systemic features require further investigation including stool culture and colonoscopy.
When to Seek Help
Severe dehydration with confusion or no urine · Bloody diarrhoea with high fever · Symptoms in a pregnant woman or infant not improving — attend A&E or call 999 immediately.
See a GP same-day if you have bloody diarrhoea, high fever, or cannot keep down fluids. Attend A&E if dehydrated, confused, or not improving after 72 hours.
Preventing Food Poisoning
Most food poisoning is preventable with proper food preparation, storage, and hygiene.
Cook meat thoroughly (especially poultry and mince) to a core temperature of 75°C. Wash hands before and after handling raw meat. Refrigerate leftovers within 1–2 hours. Clean surfaces and utensils to prevent cross-contamination.
Wash hands with soap and water for at least 20 seconds before eating, after using the toilet, and after handling raw meat. Alcohol gel is not effective against norovirus and some bacterial pathogens.
When travelling to high-risk regions, drink only bottled or boiled water, avoid ice, street food, salads washed in tap water, and raw shellfish. Take travellers’ probiotic or bismuth subsalicylate as prophylaxis.
Refrigerate foods below 5°C and freeze below -18°C. Do not leave cooked food at room temperature for more than 2 hours. Never refreeze thawed meat. Store raw and cooked foods separately in the fridge.
If unwell with vomiting or diarrhoea, do not prepare food for others. Stay off work or school until at least 48 hours after the last episode of sickness or diarrhoea. Report outbreaks in care homes or schools to Public Health.
If pregnant, avoid unpasteurised cheese and dairy, paté, raw or smoked fish, raw shellfish, and poorly cooked meat. Listeria and toxoplasma infections cause severe outcomes in pregnancy including miscarriage and stillbirth.
Getting Treatment
Most mild food poisoning is managed with oral rehydration at home. Severe dehydration, bloody diarrhoea, high fever, or vulnerable patients require urgent GP or hospital assessment. Online consultation is appropriate for mild food poisoning in otherwise healthy adults.
Expert clinical advice, when you need it.
Food Poisoning — Frequently Asked Questions
Food poisoning is caused by eating food or drink contaminated with bacteria, viruses, or toxins. The most common causes in the UK are norovirus, Campylobacter, Salmonella, E. coli, and Staphylococcal toxin. Onset is typically 1–72 hours after eating contaminated food, depending on the organism.
Most food poisoning resolves within 1–3 days without treatment. The most important intervention is oral rehydration with Dioralyte sachets or water with glucose and salt. Antiemetics (ondansetron) reduce vomiting. Antibiotics are only needed for severe cases or specific pathogens (Campylobacter, Salmonella with systemic features).
Seek medical help urgently if you have signs of dehydration (dry mouth, no urine, confusion), bloody diarrhoea, a high fever above 38.5°C, symptoms that are not improving after 72 hours, or if you are elderly, pregnant, immunocompromised, or caring for an infant with severe symptoms.
Oral rehydration salts (Dioralyte), small frequent sips of water, rest, and a bland diet when tolerated (plain crackers, rice, toast) are the foundations of home management. Avoid dairy, fatty foods, and alcohol during recovery. Do not use loperamide (Imodium) if you have bloody diarrhoea or fever.
Clostridioides difficile (C. diff) is a bacterial infection causing severe watery diarrhoea, often following antibiotic use. It destroys normal gut bacteria, allowing C. diff to overgrow and produce toxins. Treatment with fidaxomicin or oral vancomycin is required. Anti-motility agents (loperamide) must be avoided.
To prevent food poisoning: cook meat thoroughly (75°C core temperature), refrigerate food within 2 hours, wash hands before cooking and after handling raw meat, avoid cross-contamination, and do not eat food past its use-by date. When travelling abroad, follow 'boil it, cook it, peel it, or forget it'.
You are contagious for 48 hours after the last episode of vomiting or diarrhoea. Do not prepare food for others, go to work, or visit vulnerable people during this time. Inform your employer. If you work in food handling or healthcare, stay off work until 48 hours after full recovery.
If food poisoning occurs at a restaurant, takeaway, or food premises, it can be reported to the local authority Environmental Health team or to the Food Standards Agency. This helps identify outbreaks and prevent others being affected. Your GP can arrange stool culture to confirm the causative organism.