Food poisoning

Also called Gastroenteritis, Campylobacter, Salmonella, E. coli

Usually settles by itself. The danger is dehydration, and anti-diarrhoeal medicines are wrong in the cases that matter most.

What it is

Illness from eating contaminated food, most often caused by campylobacter, salmonella, E. coli, listeria or norovirus.

Most cases are unpleasant and self-limiting, resolving within a few days. The complication that matters is dehydration, particularly in babies, older people and anyone frail.

Two groups need a different approach. **E. coli O157** can cause haemolytic uraemic syndrome, a serious kidney complication, mainly in young children and older people. Antibiotics and anti-diarrhoeal medicines both increase that risk, which is why bloody diarrhoea should never be treated with loperamide and why antibiotics are avoided unless a specific diagnosis warrants them. **Listeria** is dangerous in pregnancy, causing miscarriage and stillbirth, and in immunosuppressed people.

Food poisoning is notifiable, and outbreaks in care homes, schools and food businesses must be reported to environmental health so the source can be found.

In a care setting the practical priority is the same as for norovirus: fluids, isolation, hand washing with soap and water, and prompt reporting.

Recovery is often followed by weeks of a sensitive gut, and campylobacter occasionally triggers Guillain-Barré syndrome or reactive arthritis.

Signs you might notice

Nausea, vomiting, stomach cramps, diarrhoea.

Fever, aching, headache, feeling generally unwell.

Usually starting hours to a few days after eating, depending on the organism.

Same-day help: blood in the stool; a fever above 38C persisting; vomiting that prevents keeping any fluid down; symptoms lasting more than three days; severe abdominal pain.

Signs of dehydration: dark strong urine, passing little or none, dizziness on standing, dry mouth, sunken eyes, drowsiness, and in babies fewer wet nappies and no tears.

999: drowsiness or confusion, very fast breathing, not passing urine for many hours, mottled skin, or a rash that does not fade under a glass. See sepsis.

Anybody pregnant, immunosuppressed, or over 65 with bloody diarrhoea should be assessed rather than waiting it out.

How it can affect day-to-day life

Rehydration is the treatment. Oral rehydration sachets are more effective than water alone because they replace salts as well, and they are cheap and available from any pharmacy.

Small frequent sips work when a glass does not, and this is where most home management succeeds or fails.

Loperamide is fine for ordinary travellers' diarrhoea in an adult and is wrong when there is blood or a high fever, and in young children.

Food handlers, nursery and care staff and clinical staff must stay away until 48 hours after the last episode, and that rule is widely broken under staffing pressure.

Domestic prevention is unglamorous and effective: not washing raw chicken, separate boards, cooking thoroughly, cooling and refrigerating promptly, and checking the fridge is below 5C.

For anyone with a long-term condition, illness like this is when medicines need reviewing; see the sick day rules under acute kidney injury and diabetic ketoacidosis.

Supporting someone well

Fluids, in small frequent amounts, with oral rehydration salts.

Do not use loperamide if there is blood in the stool or a high fever, and not in young children.

Do not ask for antibiotics routinely; they usually do not help and can be harmful in E. coli O157.

Stay off work, school or nursery until 48 hours after the last vomiting or diarrhoea.

Wash hands with soap and water; alcohol gel does not kill norovirus.

Report suspected outbreaks and any food business concern to environmental health.

Hold the medicines that need holding during illness, and restart them deliberately afterwards.

Get bloody diarrhoea, high fever, or dehydration assessed rather than waiting.

Watch older people and babies closely; they dehydrate fast and say little.

Where to get help

A pharmacist for rehydration salts and advice.

A GP practice or NHS 111 for blood in the stool, high fever, dehydration, or symptoms beyond three days.

999 for drowsiness, confusion, or signs of sepsis.

The local council's environmental health team for suspected outbreaks.