Food poisoning is the result of eating organisms or toxins in contaminated food. Most cases of food poisoning are from common bacteria such as Staphylococcus or E. coli.

Food poisoning can affect one person or it can occur as an outbreak in a group of people who all ate the same contaminated food.

Food poisoning tends to occur at picnics, school cafeterias, and large social functions. In these cases, food may be left out of the refrigerator too long or food preparation techniques may not be clean. Food poisoning often occurs from eating undercooked meats, dairy products, or food containing mayonnaise (like coleslaw or potato salad) that have sat out of the refrigerator too long.

Food poisoning can be caused by:

• Bacillus cereus
• Botulism
• Campylobacter
• Cholera
• E. coli enteritis
• Fish poisoning
• Listeria
• Mushroom poisoning
• Staphylococcus aureus
• Salmonella
• Shigella
• Yersinia

Botulism is a very serious form of food poisoning that can be fatal. It can come from improper home canning.

Infants and elderly people have the greatest risk for food poisoning. You are also at higher risk if:

• You have a serious medical condition, such as kidney disease or diabetes
• You have a weakened immune system
• You travel outside of the U.S. to areas where there is more exposure to organisms that cause food poisoning

Pregnant and breastfeeding women have to be especially careful to avoid food poisoning.

The symptoms from the most common types of food poisoning generally start within 2 - 6 hours of eating the food. That time may be longer (even a number of days) or shorter, depending on the cause of the food poisoning.

Possible symptoms include:

• Abdominal cramps
• Diarrhea (may be bloody)
• Fever and chills
• Headache
• Nausea and vomiting
• Weakness (may be serious and lead to respiratory arrest, as in the case of botulism)

Your health care provider will examine you for signs of food poisoning, such as tenderness in the abdomen and dehydration. Your provider will also ask about foods you have eaten recently.

Tests to find the cause may be done on your:

• Blood
• Leftover food
• Stool
• Vomit

Even if you have food poisoning, however, these tests may not be able to prove it.

In rare but possibly serious cases, your health care provider may order one or more of the following procedures:

• A thin, tube-like tool placed in the anus to look for the source of bleeding or infection (sigmoidoscopy)
• A test to measure electric impulses in the muscles (electromyography) to check for botulism
• A test of fluid from the spine (lumbar puncture) if you have signs of a nervous system disorder

You will usually recover from the most common types of food poisoning within a couple of days. The goal is to make you feel better and avoid dehydration.

• Don't eat solid foods until the diarrhea has passed, and avoid dairy products, which can worsen diarrhea (due to a temporary state of lactose intolerance).
• Drink any fluid (except milk or caffeinated beverages) to replace fluids lost by diarrhea and vomiting.
• Give children an electrolyte sold in drugstores.

If you have diarrhea and are unable to drink fluids (for example, due to nausea or vomiting), you may need medical attention and intravenous fluids. This is especially true for young children.

If you take diuretics, you need to manage diarrhea carefully. Talk to your health care provider -- you may need to stop taking the diuretic while you have the diarrhea. NEVER stop or change medications without talking to your health care provider and getting specific instructions.

For the most common causes of food poisoning, your doctor would NOT prescribe antibiotics.

If you have eaten toxins from mushrooms or shellfish, you will need medical attention right away. The emergency room doctor will take steps to empty out your stomach and remove the toxin.

Most people fully recover from the most common types of food poisoning within 12 - 48 hours. Serious complications can arise, however, from certain types of food poisoning.

Dehydration is the most common complication. This can occur from any of the causes of food poisoning.

Less common but much more serious complications include:

• Arthritis (Yersinia and Salmonella)
• Bleeding disorders (E. coli and others)
• Death (from mushrooms, certain fish poisonings, or botulism)
• Kidney problems (Shigella, E. coli)
• Nervous system disorders (Botulism, Campylobacter)
• Pericarditis (Salmonella)
• Respiratory distress, including the need for support on a breathing machine (botulism)

Call your health care provider if:

• Diarrhea lasts for more than 2 - 3 days.
• There is blood in your stools.
• You are on diuretics and have diarrhea, nausea, or vomiting.
• You have diarrhea and are unable to drink fluids due to nausea or vomiting.
• You have a fever over 101°F.

Call 911 if:

• Bleeding is excessive or your stools are maroon or black.
• You are short of breath or having trouble breathing.
• You have any nervous system symptoms such as weakness, double vision, difficulty speaking, or paralysis.
• You have signs of dehydration (thirsty, dizzy, light-headed, faint).
• You have trouble swallowing.
• You may have poisoning from mushrooms, fish, or botulism.
• Your heart is racing, pounding, or skipping.

To prevent food poisoning, take the following steps when preparing food:

• Carefully wash your hands and clean dishes and utensils.
• Use a thermometer when cooking. Cook beef to at least 160°F, poultry to at least 180°F, and fish to at least 140°F.
• DO NOT place cooked meat or fish back onto the same plate or container that held the raw meat, unless the container has been completely washed.
• Promptly refrigerate any food you will not be eating. Keep the refrigerator set to around 40°F and your freezer at or below 0°F. DO NOT eat meat, poultry, or fish that has been refrigerated uncooked for longer than 1 to 2 days.
• DO NOT use outdated foods, packaged food with a broken seal, or cans that are bulging or have a dent.
• DO NOT use foods that have an unusual odor or a spoiled taste.

• If you take care of young children, wash your hands often and dispose of diapers carefully so that bacteria can't spread to other surfaces or people.
• If you make canned food at home, be sure to follow proper canning techniques to prevent botulism.
• DO NOT feed honey to children under 1 year of age.
• DO NOT eat wild mushrooms.
• When traveling where contamination is more likely, eat only hot, freshly cooked food. Drink water only if it's been boiled. DO NOT eat raw vegetables or unpeeled fruit.
• DO NOT eat shellfish that has been exposed to red tides.
• If you are pregnant or have a weakened immune system, DO NOT eat soft cheeses, especially imported from countries outside the U.S.

If other people may have eaten the food that made you sick, let them know. If you think the food was contaminated when you bought it from a store or restaurant, tell the store and your local health department.

Archer GL. Staphylococcal infections. In: Goldman L, Ausiello D, eds. Cecil Textbook of Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 310.

Arguin P. Approach to the patient before and after travel. In: Goldman L, Ausiello D, eds. Cecil Textbook of Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 308.

Guerrant RL. Escherichia enteric infections. In: Goldman L, Ausiello D, eds. Cecil Textbook of Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 327.