All foods naturally contain small amounts of bacteria. But poor handling of food, improper cooking or inadequate storage can result in bacteria multiplying in large enough numbers to cause illness. Parasites, viruses, toxins and chemicals also can contaminate food and cause illness.
Signs and symptoms of food poisoning vary with the source of contamination, and whether you're dehydrated or have low blood pressure. Generally they include:
- Abdominal pain
- Vomiting (sometimes)
- Dehydration (sometimes)
With significant dehydration, you might feel:
- Lightheaded or faint, especially on standing
- A rapid heartbeat
Whether you become ill after eating contaminated food depends on the organism, the amount of exposure, your age and your health. High-risk groups include:
- Older adults. As you get older, your immune system may not respond as quickly and as effectively to infectious organisms as when you were younger.
- Infants and young children. Their immune systems haven't fully developed.
- People with chronic diseases. Having a chronic condition, such as diabetes or AIDS, or receiving chemotherapy or radiation therapy for cancer reduces your immune response.
If you develop food poisoning:
- Rest and drink plenty of liquids.
- Don't use anti-diarrheal medications because they may slow elimination of bacteria from your system.
Foodborne illness often improves on its own within 48 hours. Call your doctor if you feel ill for longer than two or three days or if blood appears in your stools.
Call 911 or call for emergency medical assistance if:
- You have severe symptoms, such as watery diarrhea that turns very bloody within 24 hours.
- You belong to a high-risk group.
- You suspect botulism poisoning. Botulism is a potentially fatal food poisoning that results from the ingestion of a toxin formed by certain spores in food. Botulism toxin is most often found in home-canned foods, especially green beans and tomatoes. Signs and symptoms of botulism usually begin 12 to 36 hours after eating the contaminated food and may include headache, blurred vision, muscle weakness and eventual paralysis. Some people also have nausea and vomiting, constipation, urinary retention, difficulty breathing, and dry mouth. These signs and symptoms require immediate medical attention.
- Questions and answers about foodborne illness (sometimes called "food poisoning"). Centers for Disease Control and Prevention. http://www.cdc.gov/foodsafety/facts.html. Accessed Jan. 17, 2012.
- Steckelberg JM (expert opinion). Mayo Clinic, Rochester, Minn. Jan. 27, 2012.