What is food poisoning?
Food poisoning is illness that results from eating food or drinking water contaminated with harmful germs — bacteria, viruses or parasites — or with the toxins some germs produce. It is a very common cause of the sudden diarrhoea, vomiting and stomach cramps that people often call a stomach bug. In fact, food poisoning is essentially a form of gastroenteritis where the source is specifically contaminated food or drink.
The illness happens when food is contaminated at some point before eating — through improper storage, undercooking, cross-contamination, poor hygiene during preparation, or contamination at source. Most food poisoning is unpleasant but mild, clearing up on its own within a few days as the body clears the germs or toxins. As with other causes of diarrhoea and vomiting, the main concern is dehydration from fluid loss, particularly in young children and older adults.
Symptoms and how soon they start
The symptoms of food poisoning are similar to other causes of gastroenteritis, and how soon they begin after eating can vary from a few hours to several days, depending on the germ involved. Common symptoms include:
- •Feeling sick (nausea) and being sick (vomiting)
- •Diarrhoea, sometimes with blood in certain infections
- •Stomach cramps and tummy pain
- •A high temperature
- •Aching, chills, and feeling generally unwell
- •Loss of appetite
Common causes
Food poisoning is caused by consuming food or drink contaminated with harmful germs or toxins. Contamination can happen in various ways. Common causes and sources include:
- •Bacteria such as those found in undercooked meat and poultry, or improperly stored food
- •Viruses such as norovirus, sometimes from contaminated food or an infected food handler
- •Cross-contamination between raw and cooked foods
- •Food left too long at room temperature
- •Poor hand hygiene during food preparation
- •Contaminated water, or unpasteurised products
Treatment and staying hydrated
Most food poisoning clears up on its own within a few days without specific treatment, and the priority is to stay hydrated, since diarrhoea and vomiting cause fluid loss. Drink plenty of fluids in small, frequent sips, which are easier to keep down. Oral rehydration sachets from a pharmacy help replace lost salts and fluids and are especially valuable for those at higher risk of dehydration. Rest, and eat small, plain foods when you feel able.
Antibiotics are not usually needed, as many cases are viral or resolve on their own, and are reserved for specific severe bacterial or parasitic cases identified by a doctor. Anti-diarrhoeal medicines are not always suitable, particularly for children or certain infections, so a pharmacist can advise. Most importantly, watch for signs of dehydration and other warning signs, and seek medical advice if symptoms are severe, persistent, or affecting someone in a higher-risk group. Reporting suspected food poisoning from a restaurant or shop to local authorities can also help prevent others being affected.
Preventing food poisoning
Much food poisoning is preventable through good food hygiene, often summarised as four key principles: cleaning, cooking, chilling and avoiding cross-contamination. Washing hands thoroughly before and during food preparation and after handling raw food is fundamental, as is keeping worktops, utensils and chopping boards clean.
Cooking food properly, especially meat and poultry, to the right temperature kills harmful germs, so food should be cooked thoroughly and any reheated food heated until piping hot. Chilling matters too: keeping the fridge cold enough, refrigerating perishable food promptly, and not leaving food out at room temperature for long all limit germ growth. Avoiding cross-contamination — keeping raw meat separate from ready-to-eat foods, using separate chopping boards, and storing raw food below cooked food in the fridge — prevents germs spreading between foods.
Being cautious with food and water when travelling in areas where standards may differ, checking use-by dates, and not eating food that looks or smells off all help too. These simple, consistent habits substantially reduce the risk of food poisoning, both at home and when eating out. Since anyone can be affected, good food hygiene protects the whole household, and is especially important when preparing food for higher-risk people like young children, older adults, pregnant women, or those with weakened immunity.