Food Poisoning | Symptoms, Types, Risk Factors, & Causes

Home / FoodPoisoning / Food Poisoning | Symptoms, Types, Risk Factors, & Causes

Everything You Need to Know about Food Poisoning

Foodborne illness, also known as food poisoning, is a common occurrence that can happen to anybody. Food poisoning occurs when a person eats food that has been contaminated by some sort of pathogen. Food poisoning pathogens vary wildly from viruses and bacteria to parasitic worms. The Centers for Disease Control (CDC) maintain an A-Z list of foodborne pathogens for easy reference.

Though many people have experienced food poisoning, not everybody understands this series of illnesses. People often just gloss over foodborne illnesses as “stomach bugs,” or else they just lump all foodborne illnesses together. But this can be dangerous, because not all foodborne illnesses are equally dangerous.

This article will walk you through everything you need to know about food poisoning – its symptoms and causes, who is at risk, diagnosis and treatment, and advice on how to keep you and your family safe from foodborne illness.

What Are the Symptoms of Food Poisoning?

Because foodborne illnesses are a broad category of illnesses, not one specific pathogen, there are a whole host of symptoms that people with food poisoning can experience. Some of the most common ones include:

  • Upset stomach
  • Stomach cramps
  • Nausea
  • Vomiting
  • Diarrhea
  • Fever
  • Dehydration

Symptoms of foodborne illness may take hours or even days to appear after eating contaminated food, and mostly last for a few days to a week in average cases. Symptoms may range from very mild to severe enough to require hospitalization.

Complications from food poisoning

Dehydration is the most common complication of food poisoning, because diarrhea and vomiting cause the body to lose a lot of water. So it is important in any food poisoning case to stay well hydrated by drinking enough fluids to replace those lost during the illness. If this is difficult or impossible, you may require immediate medical attention or risk becoming dangerously dehydrated.

Most cases of food poisoning clear up within a few days. In rare cases, there can be long-term complications associated with food poisoning. These include:

  • Kidney failure: This has been reported in people with serious cases of coli. This bacterium can cause a condition known as hemolytic uremic syndrome, causing damage to the blood vessels of the kidneys. This damage can lead to kidney failure.
  • Arthritis: Arthritis caused by infections like Salmonella or Campylobacter is known as reactive arthritis. It a relatively rare complication of food poisoning and usually clears up after a short episode, though it can occasionally evolve into a chronic condition.
  • Brain and nerve damage: Some foodborne pathogens like Toxoplasma gondii can cause brain and nerve damage. The most well-known foodborne illness that can damage the nervous system is botulism (Clostridium botulinum), though this is a relatively rare type of food poisoning (despite its household name).
  • Pregnancy complications: Infections by Listeria monocytogenes bacteria can cause miscarriage in early pregnancies. In later term pregnancies, Listeria can cause stillbirth, premature birth, or newborn infections right after birth.

Who Is at Risk for Food Poisoning?

The simple answer is – everybody, but not to the same degree. Food poisoning can happen to anybody because everybody eats, but some people are more susceptible than others. Here are some of the groups who may be more vulnerable to food poisoning:

Adults aged 65 and older

As our bodies age, our immune systems get worse at recognizing and killing harmful pathogens in the body. In the case of food poisoning, this results in more incidents of food poisoning in this population as well as a greater risk of hospitalization. According the CDC, nearly half of people aged 65 or older who get Salmonella, Campylobacter, Listeria or E. coli end up in the hospital.

Children under 5

On the opposite end of the spectrum, very young children have weaker immune systems because they have not had enough time to develop. This leads to a increased risk of serious foodborne illnesses and complications. Children under 5 are three times as likely to be hospitalized with Salmonella compared to the average person. And 1 in every 7 young children with an E. coli O157 infection experiences major kidney failure.

People with compromised immune systems

Cancers, autoimmune disorders, and HIV/AIDS are just some of the conditions that can compromise a person’s immune system, regardless of their age. People with these disorders are significantly more vulnerable to food poisoning. For example, Listeria infections are 50 times more likely to occur among dialysis patients compared to those who are not on dialysis.

Pregnant women

The immune system can also suffer during pregnancy. Pregnant women are 10 times more likely to be infected by Listeria compared to people who are not pregnant. Listeria is also especially dangerous among pregnant women because of the significant complications is can cause. Listeria can cause miscarriages in early phases of pregnancy. And in later phases, it can cause stillbirth. Even after birth, infants born to mothers with Listeria are at risk for serious illness or death. So pregnant women need to be extra cautious about food safety for their own health and the health of their unborn baby.

People without a secure food supply

Though this is not a physiological difference, people who experience poverty or homelessness and do not have access to a secure food supply are more likely to eat food that is unsafe, because there may be no other option. This puts them at greater risk of food poisoning.

What Are the Causes of Food Poisoning?

All cases of foodborne illness have a similar origin – they are all caused by eating food that has been contaminated. According to the CDC, these are some of the types of food that often carry foodborne pathogens:

Chicken, beef, pork, and turkey

Meat is a great environment for microbes to grow because it is rich in nutrients. Most raw poultry contains Campylobacter bacteria, which can cause food poisoning. Salmonella is also commonly found in undercooked chicken. Raw meats may contain Salmonella and E. coli among other bacteria. Additionally, raw meat may also contain tapeworm eggs and larvae. While tapeworms are not generally considered food poisoning, they are still a parasitic infection that can result from improperly cooked meat.

Washing meat and poultry before cooking does not prevent disease, and actually increases your risk of exposure to any bacteria already present in the food by splashing water around your sink and countertops. To kill any foodborne illnesses, any meat and poultry must be cooked to an appropriate internal temperature (this varies by type of meat and size of cut. Check this chart from Additionally, leftovers should be stored within two hours of cooking and not be kept longer than a few days.

Fruits and vegetables

Raw fruits and vegetables can easily harbor bacteria on their surface such as Salmonella, E. coli, and Listeria. They can be contaminated at multiple phases between farm and consumer, such as by exposure to manure on a farm or cross contamination with another food in the kitchen.

The safest way to eat fruits or vegetables to avoid foodborne pathogens is by cooking them. However, the next safest way is to wash all fruits and vegetables before eating them raw. Avoid any unwashed produce, and do not blindly trust labels that say produce is washed. It’s best to wash them anyway.

Raw milk and raw milk products

Milk from the supermarket goes through a pasteurization process, which means it is heated up to a high temperature for a very short time, just enough to kill bacteria but not enough to destroy the proteins in the milk. Raw (unpasteurized) milk can be very dangerous because it can contain bacteria like Campylobacter, Cryptosporidium, E. coli, Listeria, and Salmonella. Though raw milk may feel more “natural,” the nutritional benefits are not much different from pasteurized milk, which is much less likely to contain harmful bacteria.


Raw eggs are carriers of Salmonella. Even if the egg looks clean and uncracked, the bacteria may be present. Pasteurized eggs hold a much lower risk of harboring Salmonella than unpasteurized eggs. Whenever a recipe calls for raw or low-cooked eggs, such as homemade Caesar salad dressing or eggnog, pasteurized eggs are your best bet for preventing foodborne illness. Though the safest way to avoid foodborne illness from eggs is just to avoid these foods entirely, only eating eggs that have been cooked long enough that the yolks and the white are firm. And eating raw cookie dough that contains eggs is definitely a bad idea.

Seafood and raw shellfish

Oysters and other shellfish can contain pathogens that cause foodborne illness such as norovirus and Vibrio bacteria. Seafood should be cooked thoroughly to 145°F and reheated to 165°F.


Sprouts require warm and damp conditions to grow, which are the same conditions bacteria thrive in. So eating these types of plants, which include alfalfa and beansprouts, can be especially risky if not cooked properly. Sprouts can harbor Salmonella, E. coli, or Listeria, so raw sprouts should be avoided in favor of thoroughly cooked sprouts.

Raw flour

Processed flour is generally treated to kill bacteria and viruses, because these are easily introduced in the various stages of flour production between farm and supermarket. Raw flour has not been treated this way and can harbor dangerous bacteria. Thankfully, pathogens are killed in the baking process, so cooked baked goods are safe even when made with raw flour. However, eating any uncooked raw flour should be avoided. This includes eating raw doughs (which is doubly unsafe is the dough contains eggs).

Which Pathogens Cause Food Poisoning?

What varies case to case is which specific pathogen is causing the illness. There are many pathogens that cause foodborne illnesses. These include viruses, bacteria, and parasites. The CDC keeps a comprehensive A-Z list, but here are some of the most common foodborne pathogens according to the Food and Drug Administration (FDA):

Escherichia coli

Escherichia coli, or E. coli is a major bacterial species found in human intestines. Not every strain of E. coli cause disease, but some can cause severe illnesses.

Symptoms of E. coli include severe stomach cramps, diarrhea, and vomiting. In extreme cases, E. coli can cause hemolytic uremic syndrome, which can lead to kidney failure.

  1. coli spreads very easily through contaminated food and water, and thus has frequently been at the center of foodborne illness outbreaks around the world. According to the CDC, there have been outbreaks of E. coli every year since 2006 (possibly earlier).


In the United States, norovirus is the most common form of foodborne illness. And norovirus is especially infectious because it can also spread person-to-person, unlike most other foodborne pathogens.

Symptoms generally start within a day or two of eating the contaminated food and can include projectile vomiting, diarrhea, cramps, headache, mild fever, and muscle aches.

Because the virus is so infectious, outbreaks are common. However, outbreaks of norovirus are most common from November to April, similar to flu season.


Salmonella can easily infect many foods, including meat, eggs, fruits, vegetables, and even spices and nuts. Salmonella bacteria can cause two different diseases.

One of these, enteric fever, does not occur often within the United States because it is most commonly associated with sewage-contaminated drinking water. Enteric fevers include typhoid fever and paratyphoid fever. Enteric fever is quite serious – up to 10% of people with enteric fever who don’t get treatment may die.

The more common illness Salmonella causes is salmonellosis. This is what we know as Salmonella food poisoning. Symptoms of salmonellosis include nausea, diarrhea, vomiting, cramps, and fever. Salmonellosis is not as serious as enteric fever, and symptoms usually last just a few days, tapering off in about a week.


Campylobacter infections are one of the most common foodborne illnesses in the United States. However, unlike E. coli or norovirus, Campylobacter cases tend to be isolated and sporadic rather than associated with larger outbreaks.

Symptoms include nausea, diarrhea, vomiting, and fever. Symptoms generally appear within 2-5 days of eating contaminated food and may last up to 10 days, making Campylobacter infections more long-lasting than other foodborne illnesses like salmonellosis.

Campylobacter spreads through contaminated foods, which can include water, unpasteurized milk or cheese, undercooked poultry, and occasionally other meats and fish. It is very rarely transmitted from person to person, and in these rare cases it is usually as a result of poor hygiene by the person with the illness.

Hepatitis A

Hepatitis A is caused by the hepatitis A virus. Hepatitis A is most commonly transmitted by way of contaminated food and water, though it can also transmit person to person. Water, shellfish, and salads are the foods most often linked to hepatitis A. However, it can be difficult to trace the source of hepatitis A infection because it can take 2-4 weeks to express symptoms after exposure.

Unlike other hepatitis strains, hepatitis A generally does not lead to serious, long-term illness. The illness is usually mild and lasts a week or two. Symptoms include fever, low appetite, nausea, vomiting, diarrhea, muscle aches, and yellowing in the whites of the eyes and the skin.

Hepatitis A is also one of the only foodborne pathogens that is preventable via vaccine.


Listereia is not as common as some of the other foodborne illnesses on this list, but it is one of the most common causes of death from foodborne illnesses, so it is quite serious.

Like Salmonella, this bacterium can cause two different types of illness in people.

Noninvasive Listeria can cause mild to intense symptoms that include nausea, vomiting, aches, fever, and diarrhea. This illness is certainly not fun, but it is usually not serious and generally resolves itself. Patients may not even realize they have Listeria if it is noninvasive.

Invasive Listeria is much more dangerous. In this illness, the bacteria spreads away from the gut and can enter other parts of the body like the blood or the brain. This can cause serious complications like meningitis or damage to the brain and nervous system. In pregnant woman, Listeria infections can lead to miscarriage in early pregnancies and to stillbirth in later-term pregnancies. Listeria can also cause severe illness or death of newborns.

Diagnosing and Treating Food Poisoning

Many cases of food poisoning go undiagnosed because the illnesses often last for a short period of time, and patients just recover and go on with their lives as normal, never knowing which particular pathogen they caught. For example, the CDC reports that an estimated 29 undiagnosed cases of Salmonella occur for every single laboratory-confirmed case. Many hospitalizations and deaths from Salmonella are similarly thought to go unrecognized.

When doctors do become involved, some common foodborne pathogens can be identified with standard diagnostic tests through stool samples. Other pathogens can only be detected with more specialized equipment, but these diagnoses are not often made due to their prohibitive cost and the relative mildness of most foodborne illnesses.

The primary concern when treating foodborne illnesses is dehydration, because vomiting and diarrhea lead to significant water loss. Some recommendations for treating dehydration are:

  • Constantly replacing lost fluids and electrolytes.
  • In severe cases of diarrhea, drink a rehydration solution like Ceralyte. This can help restore electrolytes more quickly and effectively in more severe circumstances.
  • A bismuth subsalicylate preparation like Pepto-Bismol can reduce the duration and severity of diarrhea.
  • If diarrhea and cramps occur, without bloody stools or fever, taking an antidiarrheal medication may provide symptomatic relief, but these medications should be avoided if there is high fever or blood in the stools because they may make the illness worse.

Many cases of foodborne illness clear up quickly enough on their own that antibiotics are unnecessary. However, some foodborne illnesses, like Listeria can require antibiotics. Depending on the severity and type of your food poisoning your doctor will advise you on whether you need to be prescribed antibiotics.

In any illness situation, it is important to make sure you only take products and medications specifically as directed, and do not take anything if you are unsure of your reaction to it. It is better to ask your doctor and find out there’s nothing to worry about than to risk making yourself sicker taking a medication you are nervous about.

What Should I Do if I think I Have Food Poisoning?

Though food poisoning is certainly not fun, in many cases, there’s not much to do other than wait it out. Symptoms can be managed and relieved through over-the-counter medications like Pepto-Bismol, but in most the most important thing is to make sure you stay hydrated until the illness is over.

When should I go see a doctor?

Most cases of food poisoning do not require immediate medical attention. Some people with food poisoning do not even realize they have had it, since it can the form of a short, acute illness, which people often attribute to a “stomach bug.” However, if symptoms become severe, medical attention may be required. According to the CDC, you should seek medical attention if any of the following symptoms occur:

  • Bloody stools
  • High fever (temperature over 102°F, measured orally)
  • Frequent vomiting that prevents keeping liquids down (which can lead to dehydration)
  • Signs of dehydration, including little or no urination, a very dry mouth and throat, or feeling dizzy when standing up
  • Diarrhea that lasts more than 3 days

How Can I Prevent Food Poisoning?

You can protect yourself from food poisoning by following some of the advice outlined here.

  • Wash your hands well and often. It goes without saying that washing hands can help prevent disease. But especially in the context of food safety, it’s critical to wash your hands. This way if you do come across a pathogen in your food, you are less likely to get sick from it if you wash it off your hands, especially if you otherwise practice good food safety and cook food thoroughly.
  • Wash cutting boards, countertops, and dishcloths regularly and thoroughly. Keeping surfaces clean and disinfected before, during, and after cooking helps prevent the spread of pathogens in the food. Even if you cook away the Salmonella in raw chicken, it could still infect somebody eating dinner if other parts of the kitchen are not well cleaned.
  • Keep raw meat and poultry separate. Both when preparing food and when storing it, it’s important to keep potentially “germy” food away from ready-to-eat foods like raw fruits and vegetables. This can be accomplished by using separate cutting boards when preparing meats, storing them in separate areas of the fridge, and making sure that meat and poultry are wrapped and stored on lower shelves to avoid any juices dripping onto other foods.
  • Cook food thoroughly. Foods like eggs, meat, poultry, raw dairy, and even raw flour can carry bacteria if not cooked properly. While the precise amount of time food needs to cook varies depending on the type of food and the amount, there are charts and guides available on how to safely prepare meat and poultry. Eggs should be cooked until both yolk and whites are firm to ensure all bacteria have been killed.
  • Keep your fridge cold. The FDA recommends 40°F for refrigerator temperature. If your fridge is not cold enough, bacteria reproduce much more quickly. Use a refrigerator thermometer to check this and have your fridge serviced if it is not working properly. Additionally, avoid over-stuffing your fridge. This causes air to circulate poorly, which can increase the temperature.
  • Store leftovers properly. Leftovers should be stored within two hours of cooking and should not be kept longer than 2-3 days. And of course, when in doubt, throw it out. Food should only be stored and reheated once, rather than repeatedly reheated and refrigerated.
  • Respect “use-by” dates. Those dates have been set to maximize food safety. While not every food will be visibly spoiled by the date on the label, it’s safest to follow these guidelines, and in general to try not to purchase food you will not be able to finish by the time it spoils. This will save you money as well as protect you from foodborne illnesses.
  • If you have doubts about a restaurant or food stand, do not eat there. This is self-explanatory. Though modern food safety regulations keep most restaurants safe, if you have any doubts about where your food is coming from and whether you trust the kitchen it was prepared in, it is better to be safe and consider eating somewhere else. And don’t be fooled – just because a restaurant looks fancy on the outside or in the dining room does not mean it is the safest in the kitchen. Check reviews online before eating somewhere new.

Food Poisoning and Public Health

In the United States, food poisoning is a nuisance and can occasionally be quite serious, but it is also a public health issue. The CDC estimates 48 million people get sick, 128,000 are hospitalized, and 3,000 die from foodborne diseases each year in the United States. And compared to other parts of the world, the United States actually has a relatively secure supply of safe food.

Access to clean food is a major issue worldwide. The World Health Organization (WHO) reports that an estimated 600 million – almost 1 in 10 people in the world – fall ill after eating contaminated food and 420,000 die every year. 40% of these are children under 5.

Foodborne diseases are a major burden to public health. In fact, the full scope of the burden of foodborne illnesses is not known because they are in general underdiagnosed and underreported.

Food safety is linked to food security and nutrition by a vicious cycle. People without secure access to food are more likely to end up eating food that is unhealthy or unsafe, which can make them ill. Improving food safety is an important goal towards solving global issues of food security and nutrition.

To combat the public health issues of foodborne illnesses, the World Health Organization has published recommendations for policymakers in to build and maintain better food systems, including laboratories for food safety research. They also recommend integrating food safety policy into larger policy programs, like those for nutrition and food security, and considering food policy on a global scale to ensure food is safe both domestically and internationally.

However, those recommendations don’t help much in terms of what you as a consumer can do. Here are some ideas on promoting food safety on a public health level:

  • Know your food. Make sure you read labels and keep yourself aware of food hazards like the ones described in this article. Know where your food comes from, especially so that when you do get sick, you can potentially track the source and prevent others from getting sick.
  • Handle and prepare food safely. In addition to the advice described elsewhere in this article, there are plenty of guidelines available online about how to handle and cook food in the safest way possible to prevent foodborne diseases.
  • Grow fruits and vegetables safely and properly. The WHO has published guidelines on how to grow fruits and vegetables in a way that minimized microbial contamination. There is a link between hygiene in agriculture and public health. If you grow vegetables, make sure you are doing so safely, especially if you are planning to sell your crops to others.

Food Poisoning Is Painful but Preventable

This article just gave you a lot of information, but one of the most important takeaways is that in many cases, foodborne illnesses are completely preventable. It is important to educate yourself and others about food safety and be aware of what food you eat and how to prepare it.

So next time you make dinner, go to a restaurant, or even grab a snack from the fridge, make sure what you choose to eat is not just nutritious, but safe. And if you’re not sure, think about what you learned in this article. Knowledge is power, and hopefully the knowledge here will help you make great choices and keep you and your family as healthy and happy as possible.




A-Z Index for Foodborne Illness – Centers for Disease Control

Food Poisoning Symptoms – Centers for Disease Control

Food Poisoning –

Food Poisoning – Mayo Clinic

Reactive Arthritis – American College of Rheumatology

Food Poisoning – National Capital Poison Center

Most Common Foodborne Illnesses – Food and Drug Administration

Symptoms of E. coli – Centers for Disease Control

Norovirus – Centers for Disease Control

Foods That Can Cause Food Poisoning – Centers for Disease Control

Meat and Poultry Charts –

How Are Foodborne Diseases Diagnosed? – Centers for Disease Control

10 Ways to Prevent Food Poisoning – National Health Service UK

Are Your Storing Food Safely? – Food and Drug Administration

Burden of Foodborne Illness: Overview – Centers for Disease Control

Food Safety – World Health Organization

Five Keys to Growing Safer Fruits and Vegetables – World Health Organization

The Food Safety Blog Recent Outbreaks and Recalls Across the United States

NBC logo
CBS logo
inside edition
Logo of C-SPAN