Food Poisoning – Causes, Symptoms, Diagnosis, Treatment

Food poisoning is a food-borne disease. Ingestion of food that contains a toxin, chemical or infectious agent (like a bacterium, virus, parasite, or prion) may cause adverse symptoms in the body. Those symptoms may be related only to the gastrointestinal tract causing vomiting or diarrhea or they may involve other organs such as the kidney, brain, or muscle.

Foodborne illness (also foodborne disease and colloquially referred to as food poisoning)[rx] is any illness resulting from the spoilage of contaminated food, pathogenic bacteria, viruses, or parasites that contaminate food, as well as prions (the agents of “mad cow disease”), and toxins such as aflatoxins in peanuts, poisonous mushrooms, and various species of beans that have not been boiled for at least 10 minutes.

What Causes Food Poisoning?

Infections with microbes—viruses, bacteria, and parasites—cause most food poisoning.2 Harmful chemicals also cause some cases of food poisoning. Microbes can spread to food at any time while the food is grown, harvested or slaughtered, processed, stored, shipped, or prepared.

Some harmful microbes may already be present in foods when you buy them. Foods that may contain microbes include

  • fresh produce
  • raw or undercooked meat, poultry, and eggs
  • dairy products and fruit juices that have not been pasteurized—heated to kill harmful microbes
  • fish and shellfish
  • foods that people handle during preparation, sometimes called “deli foods,” such as sliced meat, salads, and cut fruit, sandwiches, and baked goods
  • processed and ready-to-eat meats such as hot dogs or deli meat
  • foods that are not properly canned or sealed

If you don’t keep raw foods such as beef, poultry, seafood, and eggs—separate from other foods, microbes from the raw foods can spread to other foods. Microbes can also spread from raw foods to your hands, kitchen utensils, cutting boards, and kitchen surfaces during food preparation. If you don’t wash your hands, utensils, cutting boards, and surfaces completely after they have come into contact with raw foods, they can spread microbes to other foods.

Microbes can cause food poisoning if you don’t take steps to kill or slow the growth of microbes in food. Microbes can grow if people don’t cook food thoroughly, keep cooked food hot, or promptly refrigerate or freeze food that can spoil.

Microbes present in the stool or vomit of people who are infected can also spread to food and cause food poisoning. People may spread these microbes to foods and drinks, especially if they don’t wash their hands thoroughly after using the bathroom, after changing a diaper, and before preparing foods and drinks.

Many bacterial, viral or parasitic agents cause food poisoning. The following table shows some of the possible contaminants when you might start to feel symptoms and common ways the organism is spread.

Contaminant Onset of symptoms Foods affected and means of transmission
Campylobacter 2 to 5 days Meat and poultry. Contamination occurs during processing if animal feces contact meat surfaces. Other sources include unpasteurized milk and contaminated water.
Clostridium botulinum 12 to 72 hours Home-canned foods with low acidity, improperly canned commercial foods, smoked or salted fish, potatoes baked in aluminum foil, and other foods kept at warm temperatures for too long.
Clostridium perfringens 8 to 16 hours Meats, stews and gravies. Commonly spread when serving dishes don’t keep food hot enough or food is chilled too slowly.
Escherichia coli (E. coli) 1 to 8 days Beef contaminated with feces during slaughter. Spread mainly by undercooked ground beef. Other sources include unpasteurized milk and apple cider, alfalfa sprouts, and contaminated water.
Giardia lamblia 1 to 2 weeks Raw, ready-to-eat produce and contaminated water. Can be spread by an infected food handler.
Hepatitis A 28 days Raw, ready-to-eat produce and shellfish from contaminated water. Can be spread by an infected food handler.
Listeria 9 to 48 hours Hot dogs, luncheon meats, unpasteurized milk and cheeses, and unwashed raw produce. Can be spread through contaminated soil and water.
Noroviruses (Norwalk-like viruses) 12 to 48 hours Raw, ready-to-eat produce and shellfish from contaminated water. Can be spread by an infected food handler.
Rotavirus 1 to 3 days Raw, ready-to-eat produce. Can be spread by an infected food handler.
Salmonella 1 to 3 days Raw or contaminated meat, poultry, milk, or egg yolks. Survives inadequate cooking. Can be spread by knives, cutting surfaces or an infected food handler.
Shigella 24 to 48 hours Seafood and raw, ready-to-eat produce. Can be spread by an infected food handler.
Staphylococcus aureus 1 to 6 hours Meats and prepared salads, cream sauces, and cream-filled pastries. Can be spread by hand contact, coughing, and sneezing.
Vibrio vulnificus 1 to 7 days Raw oysters and raw or undercooked mussels, clams, and whole scallops. Can be spread through contaminated seawater.

What Kinds of Microbes Cause Food Poisoning?

  • Viruses – Viruses invade normal cells in your body. Many viruses cause infections that can be spread from person to person. If water comes into contact with the stools of infected people, the water may become contaminated with a virus. The contaminated water can spread the virus to foods. For example, if contaminated water is used to water or wash produce, the virus can spread to the produce. Similarly, shellfish that were living in contaminated water could contain a virus. If people who are infected with a virus prepare or handle foods, they may spread the virus to the foods. Common viruses that cause food poisoning include norovirus and hepatitis A.
    • Enterovirus
    • Hepatitis A is distinguished from other viral causes by its prolonged (2–6 week) incubation period and its ability to spread beyond the stomach and intestines into the liver. It often results in jaundice, or yellowing of the skin, but rarely leads to chronic liver dysfunction. The virus has been found to cause infection due to the consumption of fresh-cut produce which has fecal contamination.[45][46]
    • Hepatitis E
    • Norovirus
    • Rotavirus
  • Bacteria – Bacteria are tiny organisms that can cause infection or disease. Bacteria can enter your body through contaminated food or water. Bacteria grow quickly when the temperature of food is between 40 and 140 degrees. Keeping food colder than 40 degrees in a refrigerator or freezer can slow or stop the growth of bacteria. Cooking food thoroughly often kills bacteria. Many types of bacteria can cause food poisoning, including
    • certain types of Salmonella
    • certain types of Clostridium, including the common C. perfringens and the less common C. botulinum, which causes an illness called botulism
    • certain types of Campylobacter, including C. jejuni
    • Staphylococcus aureus also called staph
    • Escherichia coli, also called E. coli
    • certain types of Vibrio 
    • Listeria monocytogenes also called Listeria
    • Listeria monocytogenes
    • Shigella spp.
    • Staphylococcus aureus
    • Staphylococcal enteritis
    • Streptococcus
    • Vibrio cholera, including O1 and non-O1
    • Vibrio parahaemolyticus
    • Vibrio vulnificus
    • Yersinia enterocolitica and Yersinia pseudotuberculosis
    • Brucella spp.
    • Corynebacterium ulcerans
    • Coxiella burnetii or Q fever
    • Plesiomonas shigelloides
  • Parasites – Parasites are tiny organisms that live inside other organisms. Parasites can enter your body through food or water and settle in your digestive tract. In developed countries such as the United States, parasitic infections are rare. Parasites that cause food poisoning include
    • Toxoplasma gondii, which causes an illness called toxoplasmosis
    • Giardia 
    • Cryptosporidium, which causes an illness called cryptosporidiosis or crypto
    • Platyhelminthes
      • Diphyllobothrium sp.
      • Nanophyetus sp.
      • Taenia saginata
      • Taenia solium
      • Fasciola hepatica
    • Nematode
      • Anisakis sp.
      • Ascaris lumbricoides
      • Eustrongylides sp.
      • Trichinella spiralis
      • Trichuris trichiura
    • Protozoa
      • Acanthamoeba and other free-living amoebae
      • Cryptosporidium parvum
      • Cyclospora cayetanensis
      • Entamoeba histolytica
      • Giardia lamblia
      • Sarcocystis hominis
      • Sarcocystis suihominis
      • Toxoplasma gondii
  • E. coli (Escherichia coli) – E. coli bacteria usually get into food or water when they come into contact with animal feces. Eating undercooked ground beef is the most common cause of E. coli poisoning in the United States.
  • Listeria – These bacteria are mostly found in unpasteurized dairy products, smoked seafood, and processed meats like hot dogs and luncheon meats. Listeria bacteria also can contaminate fruits and vegetables, although that’s less common.
  • Campylobacter These bacteria most commonly infect meat, poultry, and unpasteurized milk. Campylobacter also can contaminate water. As with other kinds of bacteria, these usually get into foods through contact with infected animal feces.
  • Staphylococcus aureus  – These bacteria (which can be found in meats, prepared salads, and foods made with contaminated dairy products) spread through hand contact, sneezing, or coughing. That means that people who prepare or handle food can spread the infection.
  • Shigella  Shigella bacteria can infect seafood or raw fruits and vegetables. Most of the time these bacteria spread when people who prepare or handle food don’t wash their hands properly after using the bathroom. Sometimes, an infection causes blood in the stool (poop).
  • Hepatitis A – People mostly get this virus from eating raw shellfish or foods that have been handled by someone who is infected. It can be hard to know the source of an infection because people may not get sick for 15 to 50 days afterward.
  • Noroviruses –These viruses usually contaminate the food that’s been prepared by an infected handler.

Natural toxins – Several foods can naturally contain toxins, many of which are not produced by bacteria. Plants in particular may be toxic; animals which are naturally poisonous to eat are rare. In evolutionary terms, animals can escape being eaten by fleeing; plants can use only passive defenses such as poisons and distasteful substances, for example capsaicin in chili peppers and pungent sulfur compounds in garlic and onions. Most animal poisons are not synthesised by the animal, but acquired by eating poisonous plants to which the animal is immune, or by bacterial action.

  • Alkaloids
  • Ciguatera poisoning
  • Grayanotoxin (honey intoxication)
  • Hormones from the thyroid glands of slaughtered animals (especially Triiodothyronine in cases of hamburger thyrotoxicosis or alimentary thyrotoxicosis)[rx]
  • Mushroom toxins
  • Phytohaemagglutinin (red kidney bean poisoning; destroyed by boiling)
  • Pyrrolizidine alkaloids
  • Shellfish toxin, including paralytic shellfish poisoning, diarrhetic shellfish poisoning, neurotoxic shellfish poisoning, amnesic shellfish poisoning, and ciguatera fish poisoning
  • Scombrotoxin
  • Tetrodotoxin (fugu fish poisoning)
  • Foxglove contains cardiac glycosides.
  • Poisonous hemlock (conium) has medicinal uses

What are the symptoms of food poisoning?

Common symptoms of food poisoning include

  • diarrhea or bloody diarrhea
  • vomiting
  • pain in your abdomen
  • fever
  • headache

Symptoms range from mild to severe and may last from a few hours to several days.

Less commonly, some types of food poisoning—such as botulism and fish and shellfish poisoning—can affect your nervous system. Symptoms may include

  • blurred vision
  • headache
  • paralysis
  • tingling or numbness of your skin
  • weakness

People with nervous system symptoms should see a doctor or go to an emergency room right away.

Symptoms of dehydration, the most common complication of food poisoning, may include the following in adults

  • extreme thirst and dry mouth
  • urinating less than usual
  • light-headedness; dizziness, which may occur when the person stands up; or fainting
  • feeling tired
  • dark-colored urine
  • decreased skin turgor, meaning that when you pinch and release the person’s skin, it does not flatten back to normal right away
  • sunken eyes or cheeks

If you are the parent or caretaker of an infant or a young child with symptoms of food poisoning, you should watch for the following signs of dehydration

  • thirst and dry mouth
  • urinating less than usual, or no wet diapers for 3 hours or more
  • lack of energy
  • no tears when crying
  • decreased skin turgor, meaning that when you pinch and release the child’s skin, it does not flatten back to normal right away
  • sunken eyes or cheeks

Anyone with signs or symptoms of dehydration should see a doctor or go to an emergency room right away. A person with severe dehydration may need treatment at a hospital.

Seek care right away

Food poisoning can become dangerous if it leads to severe dehydration or other complications. The symptoms listed below may suggest that an adult or child has a severe form of food poisoning, dehydration or other complications, or a serious health problem other than food poisoning. Anyone with these signs or symptoms should see a doctor right away.


Adults with any of the following symptoms should see a doctor right away

  • change in mental state, such as irritability, lack of energy, or confusion
  • high fever
  • vomiting often
  • six or more loose stools in a single day
  • diarrhea that continues for more than 3 days
  • nervous system symptoms
  • severe pain in the abdomen or rectum
  • stools that are black and tarry or contain blood or pus
  • symptoms of dehydration or other complications

Adults should also see a doctor if they aren’t able to drink enough liquids or oral rehydration solutions—such as Pedialyte, Naturalyte, Infalyte, and CeraLyte—to prevent dehydration or if they do not improve after drinking oral rehydration solutions.

Older adults, pregnant women, and adults with a weakened immune system or another health condition should also see a doctor right away if they have any symptoms of food poisoning.

Infants and children

If an infant or child has signs or symptoms of food poisoning, don’t hesitate to call a doctor for advice. Diarrhea is especially dangerous in newborns and infants, leading to severe dehydration in just a day or two. A child with symptoms of dehydration can die within a day if left untreated.

If you are the parent or caretaker of an infant or child with any of the following signs or symptoms, seek a doctor’s help right away

  • change in the child’s mental state, such as irritability or lack of energy
  • diarrhea lasting more than a day
  • any fever in infants
  • high fever in older children
  • frequent loose stools
  • vomiting often
  • nervous system symptoms
  • severe pain in the abdomen or rectum
  • signs or symptoms of complications, such as dehydration or hemolytic uremic syndrome
  • stools that are black and tarry or contain blood or pus

You should also seek a doctor’s help right away if a child has signs or symptoms of food poisoning and the child is an infant, was born prematurely, or has a history of other medical conditions. Also seek a doctor’s help right away if the child is not able to drink enough liquids or oral rehydration solutions to prevent dehydration or if the child does not improve after drinking oral rehydration solutions.

Diagnosis of Food Poisoning

Doctors often diagnose food poisoning based on your symptoms. If your symptoms are mild and last only a short time, you typically won’t need tests.

In some cases, a medical history, a physical exam, stool tests, and blood tests can help diagnose food poisoning. Your doctor may perform additional tests to check for complications or to rule out other health problems. Your doctor may need to contact the health department to report your illness.

Medical history

Your doctor will ask you about your symptoms, for example

  • what symptoms you have
  • how long you have had symptoms
  • how often you have had symptoms
  • what you recently ate and drank
  • whether you know other people who have recently had similar symptoms
  • recent travel to developing countries
  • current and past medical conditions
  • prescription and over-the-counter medicines you take

Physical exam

During a physical exam, your doctor may

  • check your blood pressure and pulse for signs of dehydration
  • examine your body for signs of fever or dehydration
  • use a stethoscope to listen to sounds in your abdomen
  • tap on your abdomen to check for tenderness or pain

Sometimes, doctors perform a digital rectal exam to check for blood in your stool. Blood in your stool may be a sign of an infection with bacteria or parasites.

  • Stool tests – A health care professional will give you a container for catching and storing the stool. You will receive instructions on where to send or take the container for analysis. Stool tests can show the presence of viruses, bacteria, or parasites.
  • Blood tests – A health care professional may take a blood sample from you and send the sample to a lab. Blood tests can show signs of certain infections or signs of complications such as dehydration.

Treatment for Food Poisoning

In most cases, people with food poisoning get better on their own without medical treatment. You can treat food poisoning by replacing lost fluids and electrolytes to prevent dehydration. In some cases, over-the-counter medicines may help relieve your symptoms.

When you have food poisoning, you may vomit after you eat or lose your appetite for a short time. When your appetite returns, you can most often go back to eating your normal diet, even if you still have diarrhea.

If your child has symptoms of food poisoning, such as vomiting or diarrhea, don’t hesitate to call a doctor for advice.

Replace lost fluids and electrolytes

When you have food poisoning, you need to replace lost fluids and electrolytes to prevent dehydration or treat mild dehydration. You should drink plenty of liquids. If vomiting is a problem, try sipping small amounts of clear liquids. Replacing lost fluids and electrolytes is the most important treatment for food poisoning.


Most adults with food poisoning can replace fluids and electrolytes with liquids such as

  • water
  • fruit juices with water added to dilute the juice
  • sports drinks
  • broths

Eating saltine crackers can also help replace electrolytes. Older adults, adults with a weakened immune system, and adults with severe diarrhea or symptoms of dehydration should drink oral rehydration solutions, such as Pedialyte, Naturalyte, Infalyte, and CeraLyte. Oral rehydration solutions are liquids that contain glucose and electrolytes.


If your child has food poisoning, you should give your child an oral rehydration solution—such as Pedialyte, Naturalyte, Infalyte, and CeraLyte—as directed. Talk with a doctor about giving these solutions to your infant. Infants should drink breast milk or formula as usual.

Over-the-counter medicines

In some cases, adults can take over-the-counter medicines such as loperamide (Imodium) and bismuth subsalicylate NIH external link (Pepto-Bismol, Kaopectate) to treat diarrhea caused by food poisoning.

These medicines can be dangerous for infants and children. Talk with a doctor before giving your child over-the-counter medicine.

If you have bloody diarrhea or fever—signs of infections with bacteria or parasites—don’t use over-the-counter medicines to treat diarrhea. See a doctor for treatment.

How do doctors treat food poisoning?

To treat food poisoning caused by bacteria or parasites, your doctor may prescribe antibiotics or medicines that target parasites, in addition to rehydration solutions.

In some cases, doctors may recommend probiotics. Probiotics are live microbes, most often bacteria, that may be similar to microbes you normally have in your digestive tract. Studies suggest that some probiotics may help shorten a bout of diarrhea. Researchers are still studying the use of probiotics to treat food poisoning. For safety reasons, talk with your doctor before using probiotics or any other complementary or alternative medicines or practices. This is especially important when children, older adults, or those with weak immune systems have diarrhea.

Doctors may need to treat people with life-threatening symptoms and complications—such as severe dehydration, hemolytic uremic syndrome, or paralysis—in a hospital.

How can I prevent food poisoning?

To prevent food poisoning at home:

  • Wash your hands, utensils, and food surfaces often – 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, preparing food, 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 tell if foods are cooked to a safe temperature is to use a food thermometer. You can kill harmful organisms in most foods by cooking them to the right 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 cooked thoroughly.
  • Refrigerate or freeze perishable foods promptly — within two hours of purchasing or preparing them. If the room temperature is above 90 F (32.2 C), refrigerate perishable foods within one hour.
  • Defrost food safely – Don’t thaw food at room temperature. The safest way to thaw food is to defrost it in the refrigerator. If you microwave frozen food using the “defrost” or “50% power” setting, be sure to cook it immediately.
  • Throw it out when in doubt – If you aren’t sure if a food has been prepared, served, or stored safely, discard it. Food left at room temperature too long may contain bacteria or toxins that can’t be destroyed by cooking. Don’t taste food that you’re unsure about — just throw it out. Even if it looks and smells fine, it may not be safe to eat.

Food poisoning is especially serious and potentially life-threatening for 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 undercooked fish or shellfish, including oysters, clams, mussels and scallops
  • Raw or undercooked eggs or foods that may contain them, such as cookie dough and homemade ice cream
  • Raw sprouts, such as alfalfa, bean, clover and radish sprouts
  • Unpasteurized juices and ciders
  • Unpasteurized milk and milk products
  • Soft cheeses, such as feta, Brie and Camembert; blue-veined cheese; and unpasteurized cheese
  • Refrigerated pates and meat spreads
  • Uncooked hot dogs, luncheon meats and deli meats
  • keep raw meat, poultry, seafood, and eggs separate from other foods
  • prepare salads and refrigerate them before handling raw meat, poultry, seafood, or eggs
  • promptly refrigerate or freeze foods that can spoil
  • wash your hands with soap and water before and after handling food
  • wash fruits and vegetables before eating, cutting, or cooking
  • cook foods long enough and at high enough temperatures to kill harmful microbes
  • wash utensils and surfaces after each use
  • don’t eat foods that can spoil that have been sitting out for more than 2 hours, or in temperatures over 90 degrees, for more than 1 hour

Food safety is especially important for people who are more likely to get food poisoning and related complications, including

  • infants and children
  • pregnant women and their fetuses
  • older adults
  • people with weak immune systems

What’s good to eat when you have food poisoning?

It’s best to gradually hold off on solid foods until vomiting and diarrhea have passed and instead ease back to your regular diet by eating simple-to-digest foods that are bland and low in fat, such as:

  • saltine crackers
  • gelatin
  • bananas
  • rice
  • oatmeal
  • chicken broth
  • bland potatoes
  • boiled vegetables
  • toast
  • soda without caffeine (ginger ale, root beer)
  • diluted fruit juices
  • sport drinks

What’s bad to eat when you have food poisoning?

To prevent your stomach from getting more upset, try to avoid the following harder-to-digest foods, even if you think you feel better:

  • dairy products, especially milk and cheeses
  • fatty foods
  • highly seasoned foods
  • food with high sugar content
  • spicy foods
  • fried foods
  • caffeine (soda, energy drinks, coffee)
  • alcohol
  • nicotine

Reduce Your Risk of Foodborne Illness

Select Safer Alternatives to High-Risk Foods

Type of Food High Risk Lower Risk
Meat and Poultry Raw or undercooked meat or poultry Meat or poultry cooked to a safe minimum internal temperature
  • Any raw or undercooked fish, or shellfish, or food containing raw or undercooked seafood (e.g., sashimi, sushi, or ceviche)
  • Cold smoked fish or products containing cold smoked fish
  • Previously cooked seafood heated to 165°F
  • Canned fish and seafood
  • Seafood cooked to 145°F
  • Fish, Smoked fish and seafood casserole heated to 165°F
  • Unpasteurized (raw) milk
  • Pasteurized milk
Eggs Foods that contain raw/undercooked eggs, such as:

  • Homemade Caesar salad dressings
  • Homemade raw cookie dough
  • Homemade eggnog
  • Homemade mayonnaise
Use pasteurized eggs/egg products when preparing recipes that call for raw or undercooked eggs
Sprouts Raw sprouts (alfalfa, bean, or any other sprout) Cooked sprouts
Vegetables Unwashed fresh vegetables, including lettuce/salads
  • Washed fresh vegetables, including salads
  • Cooked vegetables
Cheese Soft cheeses made from unpasteurized (raw) milk, such as:

  • Feta, Brie
  • Camembert
  • Blue-veined
  • Queso fresco
  • Hard cheeses
  • Processed cheeses
  • Cream cheese
  • Mozzarella
  • Soft cheeses that are clearly labeled “made from pasteurized milk”
Hot Dogs and Deli Meats Hot dogs, deli and luncheon meats that have not been reheated Reheat hot dogs, luncheon meats, and deli meats to steaming hot or 165ºF
Pâtés Unpasteurized and/or refrigerated pâtés or meat spreads Canned or shelf-stable pâtés or meat spreads

Travelers’ diarrhea

To reduce your chances of getting travelers’ diarrhea when traveling to developing countries, avoid eating or drinking the following

  • unbottled or untreated water. Also, avoid brushing your teeth with unbottled or untreated water. Tap, well, lake, or river water may contain microbes.
  • ice, foods, and drinks prepared with untreated tap or well water.
  • unpasteurized juice, milk, and milk products like cheese or yogurt. Pasteurization kills harmful microbes.
  • food or drinks from street vendors.
  • warm food that was not served hot.
  • raw or undercooked meat, fish, or shellfish.
  • raw vegetables and fruits that you have not washed in clean water or peeled yourself.

If you are worried about travelers’ diarrhea, talk with your doctor before traveling. Your doctor may recommend ways that you can treat local water to kill or remove harmful microbes. Your doctor may also recommend that you bring antibiotics with you in case you get diarrhea during your trip. Early treatment with antibiotics can shorten a case of travelers’ diarrhea. Doctors may prescribe an antibiotic such as rifaximin (Xifaxan) or rifamycin (Aemcolo)  to treat adults with travelers’ diarrhea caused by certain strains of Escherichia coli E. coli) who do not have fever or blood in the stool? For severe travelers’ diarrhea, your doctor may prescribe azithromycin (Zithromax, Zmax)  or ciprofloxacin (Cipro) .

Doctors may advise some people—especially people with weakened immune systems—to take antibiotics before and during a trip to help prevent travelers’ diarrhea.

Complications are uncommon in the UK. Those who are older are more likely to develop complications. Complications are also more likely if you have an ongoing (chronic) condition such as diabetes or if your immune system is not working normally. (For example, if you are taking long-term steroid medication or you are having chemotherapy treatment for cancer.) Possible complications include the following:

  • Salt (electrolyte) imbalance and lack of fluid (dehydration) in your body – This is the most common complication. It occurs if the salts and water that are lost in your stools (feces), or when you are sick (vomit), are not replaced by you drinking adequate fluids. If you can manage to drink plenty of fluids then dehydration is unlikely to occur, or is only likely to be mild, and will soon recover as you drink. Severe dehydration can lead to a drop in your blood pressure. This can cause reduced blood flow to your vital organs. If dehydration is not treated, your kidneys may be damaged. Some people who become severely dehydrated need a ‘drip’ of fluid directly into a vein. This requires admission to the hospital. People who are elderly or pregnant are more at risk of dehydration.
  • Reactive complications – Rarely, other parts of your body can ‘react’ to an infection that occurs in your bowels. This can cause symptoms such as joint inflammation (arthritis), skin inflammation, and eye inflammation (either conjunctivitis or uveitis).
  • Spread of infection – to other parts of your body such as your bones, joints, or the meninges that surround your brain and spinal cord. This is rare. If it does occur, it is more likely if diarrhea is caused by salmonella infection.
  • Irritable bowel syndrome – is sometimes triggered by a bout of food poisoning.
  • Lactose intolerance – can sometimes occur for a period of time after food poisoning. This is known as ‘secondary’ or ‘acquired’ lactose intolerance. Your bowel (intestinal) lining can be damaged by an episode of bowel infection. This leads to a lack of a chemical (enzyme) called lactase that is needed to help your body digest a sugar called lactose that is in milk. Lactose intolerance leads to bloating, tummy (abdominal) pain, wind, and watery stools after drinking milk. The condition gets better when the infection is over and the bowel lining heals. It is more common in children than in adults.
  • Haemolytic uraemic syndrome – is another potential complication. It is rare and is usually associated with food poisoning caused by a certain type of E. coli infection. It is a serious condition where there is anemia, a low platelet count in the blood, and kidney failure. It is more common in children. If recognized and treated, most people recover well.
  • Guillain-Barré syndrome – may rarely be triggered by campylobacter infection. This is a condition that affects the nerves throughout your body and limbs, causing weakness and sensory problems.
  • Reduced effectiveness of some medicines – During an episode of food poisoning, certain medicines that you may be taking for other conditions or reasons may not be as effective. This is because diarrhea and/or vomiting means that reduced amounts of the medicines are taken up (absorbed) into your body. Examples of such medicines are those for epilepsy, diabetes, and contraception. Speak with your doctor or practice nurse if you are unsure of what to do if you are taking other medicines and have food poisoning.


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