Food poisoning, also called foodborne illness, is a disease caused by eating contaminated food. Infectious organisms – including bacteria, viruses, and parasites – or their toxins are the most common causes of food poisoning.
Infectious organisms or their toxins can contaminate food at any processing or production site. Contamination can also occur at home when food is mishandled or cooked.
Symptoms of food poisoning that may occur within hours of eating contaminated food often include nausea, vomiting, or diarrhea. Most of the time, food poisoning is mild and resolves without treatment. But some people need to go to the hospital.
Food poisoning symptoms vary with the source of contamination. Most types of food poisoning cause one or more of the following signs and symptoms:
- Watery or bloody diarrhea
- Abdominal pain and cramps
Signs and symptoms may begin within hours of eating the contaminated food or start days or even weeks later. Illness caused by food poisoning generally lasts from a few hours to several days.
When to see a doctor
If you experience any of the following signs or symptoms, seek medical attention.
- Frequent episodes of vomiting and inability to keep fluids down
- Bloody vomit or stool
- Diarrhea for more than three days
- Extreme pain or severe abdominal cramps
- An oral temperature higher than 100.4 F (38 C)
- Signs or symptoms of dehydration-excessive thirst, dry mouth, little or no urination, severe weakness, dizziness, or lightheadedness
- Neurological symptoms such as blurred vision, muscle weakness, and tingling in the arms
Contamination of food can happen at any point of production: Growing, harvesting, processing, storing, shipping or preparing. Cross-contamination-the transfer of harmful organisms from one surface to another-is often the cause. This is especially problematic for raw, ready-to-eat foods such as salads or other produce. Because these foods are not cooked, harmful organisms are not destroyed before eating and can cause food poisoning.
Many bacterial, viral, or parasitic agents cause food poisoning. The following table shows some of the possible contaminants when you can feel symptoms and common ways the organism spreads.
Whether you get sick after eating contaminated food depends on the organism, the amount of exposure, your age, and your health. Risk groups include:
As you get older, your immune system may not respond as quickly or effectively to infectious organisms as it used to.
Pregnant. During pregnancy, changes in your metabolism and circulation may increase your risk of food poisoning. Your reaction may be more severe during pregnancy. Rarely, your baby may also get sick.
Infants and young children. Their immune systems are not fully developed.
People with chronic diseases. A chronic disease – such as diabetes, liver disease, or AIDS – or chemotherapy or radiation therapy for cancer reduces your immune response.
The most common serious complication of food poisoning is dehydration – a severe loss of water and essential salts and minerals. If you are a healthy adult and drink enough to replace fluids you lose through vomiting and diarrhea, dehydration should not be a problem.
Infants, older adults, and people with suppressed immune systems or chronic illnesses can become severely dehydrated if they lose more fluids than they can replace. In this case, they may need to be hospitalized and receive intravenous fluids. In extreme cases, dehydration can be fatal.
Some types of food poisoning have potentially serious complications for certain people. These include:
Listeria infection. Complications of Listeria food poisoning can be most severe for an unborn baby. Early in pregnancy, a Listeria infection can cause miscarriages. Later in pregnancy, Listeria infection can lead to stillbirths, premature births, or potentially fatal infection of the baby after birth – even if the mother was only mildly ill. Infants who survive a Listeria infection may experience long-term neurological damage and delayed development.
Escherichia coli (E. coli). Certain strains of E. coli can cause a serious complication called hemolytic uremic syndrome. This syndrome damages the lining of tiny blood vessels in the kidneys and sometimes leads to kidney failure. Older adults, children under age 5, and people with weakened immune systems are at higher risk of developing this complication. If you are in one of these risk categories, see your doctor at the first sign of severe or bloody diarrhea.
To prevent food poisoning at home:
Wash your hands, utensils, and food surfaces frequently. Wash your hands well with warm, soapy water before and after handling or preparing food. Use hot soapy water to wash utensils, cutting boards, and other surfaces you use.
Keep raw foods separate from ready-to-eat foods. When shopping for, preparing, or storing food, keep raw meat, poultry, fish, and shellfish away from other foods. This prevents cross-contamination.
Cook foods to a safe temperature. The best way to determine if food is cooked to a safe temperature is to use a food thermometer. You can kill harmful organisms in most foods by cooking them to the proper temperature.
Cook ground beef to 160 F (71.1 C), steaks, roasts and chops, such as lamb, pork and veal, to at least 145 F (62.8 C). Cook chicken and turkey to 165 F (73.9 C). Make sure fish and shellfish are thoroughly cooked.
Refrigerate or freeze perishable foods immediately – within two hours of purchase or preparation. If room temperature is above 90 F (32.2 C), refrigerate perishable foods within one hour.
Defrost foods safely. Do not thaw foods at room temperature. The safest way to thaw food is to thaw it in the refrigerator. If you microwave frozen food on the “defrost” or “50% power” setting, cook it immediately.
When in doubt, throw it out. If you are not sure if a food was safely prepared, served or stored, discard it. Food left at room temperature too long may contain bacteria or toxins that cannot be destroyed by cooking. Don’t try food you’re not sure about – just throw it away. Even if it looks and smells good, it may not be safe to eat.
Food poisoning is especially serious and potentially life-threatening to young children, pregnant women and their fetuses, older adults, and people with weakened immune systems. These individuals should take extra precautions by avoiding the following foods:
- Raw or rare meat and poultry
- Raw or uncooked fish or shellfish, including oysters, clams, mussels and scallops
- Raw or uncooked eggs or foods that may contain them, such as cookie dough and homemade ice cream
- Raw sprouts such as alfalfa, beans, clover and radishes
- Unpasteurized juices and cider
- Unpasteurized milk and milk products
- Soft cheeses such as feta, brie and camembert; blue cheese; and unpasteurized cheese
- Chilled pies and meat spreads
- Uncooked hot dogs, lunch meats and sausages