What Is the Most Common Cause of Food Poisoning?

It is a highly contagious virus that can reach food when an infected person handles it, or when food or water becomes contaminated during production, preparation, or serving. Other viruses, bacteria, and toxins can also cause foodborne illness, so symptoms alone cannot identify the exact cause.

Food poisoning can irritate the digestive tract and cause sudden nausea, vomiting, watery diarrhoea, abdominal pain, or fever. A person may become unwell after eating contaminated food, but the food that caused the illness is not always the most recent meal. Symptoms can also spread from person to person, especially through unwashed hands and shared surfaces.

The main immediate concern is fluid loss from vomiting and diarrhoea. Children, older adults, pregnant people, and people with long-term medical conditions may become dehydrated more quickly and may need advice sooner. Read more about [Food Poisoning](/conditions/food-poisoning/), [Diarrhoea](/symptoms/diarrhoea/), [Vomiting](/symptoms/vomiting/), and [Nausea](/symptoms/nausea/).

Take frequent small sips of water or an oral rehydration solution. Oral rehydration solution replaces water and important salts lost through diarrhoea or vomiting; follow the product instructions when preparing it. If drinking triggers vomiting, pause briefly and try smaller sips again.

Rest, eat when you feel able, and choose simple foods that you tolerate. Wash your hands carefully with soap and water, clean contaminated surfaces, and avoid preparing food for other people while you are ill. Do not share towels or utensils if possible. [Oral Rehydration Therapy](/treatments/acute-and-urgent-care/oral-rehydration-therapy/) explains how fluid replacement is used.

Seek urgent medical help if you cannot keep fluids down, have signs of dehydration such as very little urine, marked dizziness, confusion, or unusual sleepiness, or develop severe or worsening abdominal pain. Blood in vomit or stool, a high fever, or trouble breathing also needs prompt assessment.

Contact a clinician if symptoms are not improving, if you have a weakened immune system, or if you are concerned about a child, older adult, or pregnant person. A healthcare professional can assess hydration and decide whether tests or treatment such as [IV Fluid Therapy](/treatments/acute-and-urgent-care/iv-fluid-therapy/) is needed. [Abdominal Pain](/symptoms/abdominal-pain/) and [Fever](/symptoms/fever/) provide more symptom-specific guidance.

Ask which fluids are suitable, whether any medicines should be avoided, and what signs would mean you need reassessment. Tell the clinician when symptoms began, whether you can drink and urinate normally, what foods others shared, and whether anyone else became ill.