What You Should Know About Food Poisoning

Medically Reviewed by Neha Pathak, MD on September 17, 2021
Written by WebMD Editorial Contributors
11 min read

If you’ve ever had food poisoning, you probably had a good idea that’s what it was even before you talked to your doctor. It’s hard to miss the main symptoms: stomach cramps, vomiting, and diarrhea. They can hit a few hours or a day or two after you eat the food that caused the problem.

Your symptoms usually pass in a few days or even in mere hours. But if your discomfort doesn’t go away, you may need to get checked and find out exactly what made you sick. You should also see a doctor if along with other symptoms you have high fever, blood in your stool, or feel dehydrated or unable to keep any food or liquid down.

Your doctor may be able to tell you what caused it after running tests. But they aren’t always necessary and don’t confirm every case.     

Many times, your doctor will diagnose food poisoning based simply on your symptoms. While the main symptoms are nausea, diarrhea, vomiting, and stomach cramps, you also may have a fever, headache, muscle and joint aches, or blood in your stool. You may also be dehydrated, so your mouth and throat feel dry and you don’t pee as often as you typically do. Dehydration can make you dizzy when you stand up. Rarely, food poisoning can cause blurry or double vision, tingling, or weakness.

More than 250 bacteria, viruses, and parasites are known to cause food poisoning. They can exist in foods at any stage, such as when they're growing, packaged, shipped, stored, or cooked.

Certain foods are more likely to harbor bad germs. These include raw eggs, unpasteurized milk and juice, soft cheeses, and raw or undercooked meat or seafood. Fresh produce is another risk. Foods made in bulk are problematic, too. A single bad egg could affect the whole batch of omelets in a buffet. You could make trouble for yourself by not washing the cutting board or your hands as you prepare different foods.

Your chances of getting food poisoning are higher in the summer. In 90-degree heat, food can start to spoil within an hour. At a picnic or during a camping trip, you are more likely to eat undercooked grilled meats or to handle raw meat without access to soap and water. Bacteria can grow quickly inside tepid coolers. So if you're picnicking on a hot day, put leftovers back in with fresh ice.

In 4 out of 5 cases of food poisoning, you never find out exactly what caused it. That's OK because you most likely will get better on your own. But in cases where the culprit is found, it's usually one of the following:

  • Norovirus, often called stomach flu, is behind more than half of the foodborne illnesses in the U.S. where the cause is known. Norovirus can sicken you not only through eating contaminated foods, but also through touching doorknobs and other surfaces or having contact with an infected person. You should wipe down the kitchen if someone in your house has it. It typically takes 12-48 hours before you feel sick. Your symptoms may last 1-3 days.
  • Salmonella is the name of a group of bacteria. They grow in undercooked eggs and meat. But you can also get salmonella from unpasteurized milk or cheese. Some fruits and vegetables, such as melons or sprouts, can also cause it. Symptoms start within 1-3 days and can last up to a week.
  • Clostridium perfringens are bacteria that are more likely to show up when foods are prepared in bulk, such as in cafeterias or nursing homes or for catered events. Cooking kills the bacteria but not its spores. So food left warming can grow new germs. You can get it from beef, chicken, or gravy. You may have cramps and diarrhea but no other symptoms. You get sick within 6-24 hours and are usually feeling better in a couple of days.
  • Campylobacter comes from undercooked poultry, unpasteurized milk, and sometimes water. It may take 2-5 days to develop symptoms you can notice. But you should feel better in another 2-10 days. You can't pass it to anyone. But if it's serious, you might have bloody diarrhea.

Some bacteria cause fewer cases of food poisoning but can make you very sick. They can even cause death.

They include:

  • E. coli, a type of bacteria found in the intestines of animals. You can get this from undercooked ground beef, unpasteurized milk, sprouts, or any food or liquid that has had contact with animal feces or sewage. Some strains are harmless. Others can make you very sick.
  • Listeria is an unusual bacteria that can grow in cold temperatures such as in the refrigerator. It's found in smoked fish, raw (unpasteurized) cheeses, ice cream, pates, hot dogs, and deli meats. Typically, symptoms start within 24 hours of eating the product and you have short-lived gastroenteritis with watery diarrhea, nausea, vomiting, and sometimes fever. That said, it can be much more serious in older people, pregnant women, or those with weakened immune systems. The bacteria can enter the bloodstream and central nervous system and cause an infection called listeriosis. This usually happens within 10 days to a month after exposure. In addition to diarrhea and vomiting, listeria can cause unusual symptoms, including weakness, confusion, and a stiff neck. It can also be deadly. If you have any of these symptoms, call your doctor right away.

If your illness is severe or complicated, your doctor may run some of the following tests. 

Stool cultures are the most common lab test for food poisoning. Your doctor may order one if you have a fever, ntense stomach pain, or bloody diarrhea, or if there is an outbreak that is being tracked. They may also order one if you have symptoms that linger. A sample of your stool can help tell if your sickness is related to bacteria. It can even reveal the germ’s DNA “fingerprint” and which antibiotics will kill it. Viruses are more difficult to see in culture,  so if the specific virus needs to be identified, your doctor may order stool tests to look for the germ's DNA fingerprint.Microscopic exams of stool can identify parasites. Stool tests aren’t always accurate, and they can take several days to come back.

Blood tests may be ordered if your doctor thinks the infection has spread into the blood. Blood tests can detect the bacteria Listeria monocytogenes and the hepatitis A virus. Specific blood tests can tell how sick you are by looking for inflammation and signs that you’re dehydrated.

Stool or blood tests can check for toxins, such as for botulism, which can be deadly.

Imaging tests such as MRIs and CT scans aren’t often used in food poisoning cases. But they can help rule out other causes for your symptoms.     

A host of other conditions can lead to many of the same symptoms of food poisoning. Most common is mon-foodborne  gastroenteritis, which is most often caused by a virus. For instance, Norovirus causes both foodborne gastroenteritis (from contaminated food or water) and viral gastroenteritis from person to person spread. Other causes include gallbladder problems, pancreatitis, and inflammatory bowel disease. So figuring out if you have food poisoning is as much about the timing as it is about the symptoms themselves.

In most cases, food poisoning usually shows up hours or days after you’ve eaten something that made you sick.  That can make it hard to know if it's food poisoning or something else. The delay also makes it tricky to trace the illness back to the specific food or drink.

But different organisms work at different speeds. For example, Staphylococcus aureus can give you cramps, diarrhea, and nausea in as little as 30 minutes after you eat or drink. This bacterium grows in meats, eggs, and cream that haven’t been refrigerated properly. Another, far less common, cause of foodborne illness is the hepatitis A virus. It can lie in wait as long as 50 days before making itself known.

You can get the virus through foods and drinks that have been in contact with sewage water. You’re more likely to get the virus when traveling in developing countries.

Call 911 if you think the food poisoning may be from seafood or wild mushrooms, or if the person is severely dehydrated.

First, control nausea and vomiting:

  • Avoid solid foods until vomiting ends. Then eat light, bland foods, such as saltine crackers, bananas, rice, or bread.
  • Sipping liquids may help avoid vomiting.
  • Don’t eat fried, greasy, spicy, or sweet foods.
  • Don’t take anti-nausea or anti-diarrhea medication without asking your doctor. They have side effects and may make some kinds of diarrhea worse. Your doctor may give you anti-nausea medication if you are at risk of being dehydrated.

It’s important to prevent dehydration:

  • Drink clear fluids, starting with small sips and gradually drinking more.
  • If vomiting and diarrhea last more than 24 hours, drink an oral rehydration solution.

Call a doctor right away if symptoms last more than 3 days or you have:

Food safety for high-risk groups

Food poisoning is more common and riskier for people with weakened immune systems, infants and young children, pregnant women, and the elderly. If you fall into one of these groups, try to avoid:

  • Sushi and other raw seafoods and partly cooked shellfish like mussels, clams, and scallops.
  • Refrigerated smoked seafood. These usually have labels that say “Nova-style,” “lox,” “kippered,” “jerky,” or “smoked.” Smoked seafood should be safe if you cook it well or if it has been canned or stored on a shelf.
  • Unpasteurized juice and cider, including fresh-squeezed. These drinks can be safe if you boil them for 1 minute.
  • Soft cheeses (Brie and Camembert), blue-veined cheeses (Roquefort) and Mexican-style cheeses (queso blanco, queso fresco, Panela). These are often made from unpasteurized milk, especially when they’re sold at farmer’s markets. Feta is also often made with raw milk. Stick with hard cheeses like cheddar or Swiss.
  • Raw or partly cooked eggs. That means staying away from cookie and cake batter (not even a lick of the spoon). Same for homemade eggnog, tiramisu, Caesar dressing, hollandaise sauce, and ice cream. If you buy one of these products at the store, check the label to make sure it doesn’t contain raw eggs. At home, cook eggs until the yolk is hard.
  • Raw or undercooked sprouts such as alfalfa, clover, mung beans, and radishes.
  • Premade salads from the deli that contain meat or seafood. Canned versions are safe.
  • Pâtés or meat spreads that have been refrigerated (they may be unpasteurized).
  • Hot dogs, cold cuts, and luncheon and deli meats, even if they’re labeled cooked. Eat them only after you’ve reheated them steaming hot. Make sure no juices from these products end up on your hands or on plates, utensils, or counters.

Food safety in the grocery store

Before you load items into the shopping cart:

  • Check the ingredients for unpasteurized milk or raw eggs. Make sure the “sell by” date hasn’t passed.
  • Don’t buy food in dented or bulging cans or in damaged packaging.
  • Pick up meat, poultry, and seafood just before you check out to limit the time they go unrefrigerated. Wrap meats in separate plastic bags so they don’t touch other items.
  • Go directly home after you buy your food, and put away refrigerated items right away.

Food safety in the kitchen

These tips will help make your home-cooked meals safe:

  • Wash your hands with soap and water for at least 20 seconds. Also wash hands during cooking and preparations if you switch from one food to another. Keep countertops clean.
  • Rinse all fruits and vegetables, even if you’re not going to eat the skin.
  • Don’t let raw meat, poultry, seafood, and eggs come into contact with other foods on cutting boards, countertops, utensils, and other surfaces. Don’t touch any foods if you have symptoms of food poisoning.
  • Wash cutting boards and knives with antibacterial soap and warm to hot water after handling raw meat, poultry, seafood, or eggs. Wooden cutting boards are not recommended because they can be harder to clean.
  • Do not thaw foods at room temperature. Thaw foods in the refrigerator, and use them promptly. Do not refreeze foods if they have been thawed all the way.
  • Don’t set out eggs, meats, poultry, seafood, or milk at room temperature for long.
  • Cooking kills bacteria. Use a thermometer to make sure meats are cooked to safe temperatures. For beef and pork, it’s 145 F. For poultry, it’s 165 F.
  • Keep your fridge temperature below 40 F and your freezer at 0 F.

Food safety while eating out

You have more control over the safety of  foods cooked at home than in a restaurant. But you can still take some safe steps when eating out:

  • Choose where you eat carefully. If the restaurant looks dirty to you, it could be a sign that it isn’t handling or serving food properly. People who eat often at fast-food restaurants are more likely to report stomach issues than those who don’t visit as often. Check with your local health department’s restaurant inspection reports. Some states and cities require restaurants to post their health ratings in a visible spot.
  • Always ask for your hamburger or other ground meat well done. For whole steak, roast, or a chop, medium rare (145 F) can be safe. Raw-meat dishes like steak tartare are risky.
  • Make sure there are no raw or undercooked eggs in anything you order.
  • If you take home food, put it in the fridge within 2 hours of leaving the restaurant. If it’s above 90 F outside, make that 1 hour.

Food safety while traveling

Who doesn’t love a vacation? But you need to be careful when you travel, especially to developing countries.

  • Eat packaged or dry foods. Many of the bugs that cause food poisoning prefer moisture. Dry foods such as bread or chips or factory-sealed foods such as tuna are usually a safe bet.
  • Go for bottled, canned, or hot drinks. Carbonated drinks are a good choice, because the bubbles will tell you it’s been sealed properly. You should be good with coffee or tea if it arrives steaming hot.
  • Avoid raw food, local wild game, and tap water and ice in developing countries.

Other safety tips

  • Breastfeed your baby if possible. Mother's milk is the safest food for young infants. Breastfeeding may prevent many foodborne illnesses and other health problems.
  • Wash your hands with soap after handling reptiles, turtles, birds, or after contact with human or pet feces.
  • If you have diarrhea or vomiting, do not prepare food for others, especially people in high-risk groups.
  • Always wash your hands before preparing food or eating.
  • Always wash your hands after using the toilet, changing diapers, or coughing or sneezing.
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