Food poisoning, also called foodborne illness, is illness 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 point of processing or production. Contamination can also occur at home if food is incorrectly handled or cooked.
Food poisoning is a major cause of gastroenteritis, resulting in a well-known set of unpleasant symptoms.
Gastroenteritis is usually caused by viruses, bacteria, or parasites; when the source of such infection is contaminated food, it is called food poisoning. Gastroenteritis may also be referred to as “gastric flu” or “stomach flu.”
Getting sick from eating food that has germs, viruses, or parasites is more common than you might think. An estimated 48 million Americans, that’s 1 out of every 6, come down with food poisoning every year. Most get better on their own without medical treatment.
The most common symptoms are abdominal cramping, nausea, vomiting, and diarrhea. The symptoms usually start within hours or days after eating a contaminated food. But sometimes the symptoms can take days or more than a week to show up. 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.
What Is Food Poisoning?
Food poisoning is caused by bacteria, viruses or toxins in the food we eat. Some of these toxins are found naturally in foods, while some have accumulated in the environment.
If you have food poisoning you’ll probably have gastroenteritis symptoms such as abdominal cramps, diarrhoea or vomiting, or flu-like symptoms. Food poisoning can also cause serious long-term problems like kidney failure. Occasionally people die from food poisoning.
Some wild mushrooms, including the death cap, are extremely poisonous. You should not eat wild-harvested mushrooms unless they have been definitely identified as safe. Seek immediate medical treatment If you think you may have eaten poisonous mushrooms.
Large fish, such as shark, swordfish and marlin, may accumulate relatively high levels of mercury. You should limit your consumption of these fish, especially if you are a child, are pregnant or planning pregnancy.
Common Food Poisoning Symptoms
Cramps in your stomach and gut, diarrhea, and vomiting may start as early as 1 hour after eating tainted food and as late as 10 days or longer. It depends on what is causing the infection.
Some other possible, common symptoms of a variety of food poisonings might include:
- Bloating and gas
- Muscle aches
- Belly pain and cramping
Symptoms of Food Poisoning That Could Be Life-Threatening
Some symptoms mean you should seek medical help:
- Repeated vomiting; not being able to hold anything down
- Signs of dehydration: dry mouth, little or no urination, dizziness, or sunken eyes
- Any diarrhea in a newborn or infant
- Diarrhea that lasts longer than 2 days (1 day in a child) or is severe
- Severe gut pain
- Fever of 102 F or higher, or a rectal temperature of 100.4 F in a baby younger than 3 months
- Black, tarry, or bloody stools
- Muscle weakness
- Tingling in your arms
- Blurry vision
- Diarrhea or flulike illness in pregnant women
- Jaundice (yellow skin), which can be a sign of hepatitis A
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.
More Serious Causes
Some bacteria cause fewer cases of food poisoning but can make you very sick. They can even cause death.
- E. coli. This is the name of 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 bacterium 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 occur within 24 hours of ingesting the product and you experience short-lived gastroenteritis with watery diarrhea, nausea, vomiting and sometimes fever. That said, it can be much more serious in older, pregnant or immunocompromised people. The bacterium can enter the bloodstream and central nervous system and cause an infection called listeriosis. Tis usually happened 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 you think you may have food poisoning, talk to your doctor.
What Germs Cause Food Poisoning?
Germs that often cause food poisoning include:
Salmonella. Salmonella bacteria are the leading cause of food poisoning in the United States. These bacteria usually get into foods when they come into contact with animal feces. The main causes of salmonella poisoning are eating dairy products, undercooked meat, and fresh produce that hasn’t been washed well.
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 food that’s been prepared by an infected handler.
Some of these, including Listeria and E. coli, can cause potentially dangerous heart, kidney, and bleeding problems.
How Is Food Poisoning Diagnosed?
Your doctor may be able to diagnose the type of food poisoning based on your symptoms. In severe cases, blood tests, stool tests, and tests on food that you have eaten may be conducted to determine what is responsible for the food poisoning. Your doctor may also use a urine test to evaluate whether an individual is dehydrated as a result of food poisoning.
astroenteritis and food poisoning usually resolve themselves without any medical intervention. Treatment is focused on reducing the symptoms and preventing complications, especially dehydration.
The main treatment and prevention strategy for food poisoning is to rest and replace lost fluids and electrolytes by:
- Drinking plenty of liquids (preferably with oral rehydration salts to replace lost electrolytes – see below)
- Ensuring fluid intake even if vomiting persists, by sipping small amounts of water or allowing ice cubes to melt in the mouth.
- Gradually starting to eat again. No specific restrictions are recommended, but blander foods might be easier to start with (cereal, rice, toast, and bananas are good examples).
The following may worsen symptoms during gastroenteritis episodes: fatty, sugary, or spicy foods, dairy products, caffeine, and alcohol.
To avoid the dangerous and potentially fatal effects of dehydration from diarrhea, oral rehydration salts (ORS) are recommended for vulnerable people (for example, infants and children, adults over 65 years of age, and people with weakened immunity).
Use of ORS in developing countries has been “one of the great public health success stories of our time,” according to a former director-general of the World Health Organization (WHO), Dr. Gro Harlem Brundtland – it reduced the number of deaths every year among children with acute diarrhea, from 5 million to 1.3 millionTrusted Source deaths.
In developed countries, while the threat of death is smaller, rehydration is nonetheless important.
Salt, glucose, and minerals lost through dehydration are replaced by sachets of oral rehydration salts available from pharmacies and online. The salts are dissolved in drinking water and do not require a doctor’s prescription.
It is important to get the right concentration, as too much sugar can make diarrhea worse, while too much salt can be extremely harmful, especially for children. A more dilute solution (for instance using more than 1 liter of water), is preferable to a more concentrated solution.
Store-bought products like Pedialyte and Gatorade also help restore electrolytes and increase hydration.
Drug treatments for Gastroenteritis
Drugs are available to reduce the main symptoms of gastroenteritis – diarrhea and vomiting:
- Antidiarrheal medication such as loperamide (branded versions include Imodium, and Imotil, among others) and bismuth subsalicylate (for example, Pepto-Bismol)
- Antiemetic (anti-vomiting) medication such as chlorpromazine and metoclopramide
Antidiarrheals are available OTC, while the antiemetics are available from doctors
Talk to a doctor before taking anti-diarrhea medication as some infections may get worse with anti-diarrhea medicines.
How Can We Prevent Food Poisoning?
Follow these tips to help protect your family from food poisoning:
- Teach everyone in your family to wash their hands well and often, especially after using the bathroom, before touching food, and after touching raw food. Use soap and warm water and scrub for at least 15 seconds.
- Clean all utensils, cutting boards, and surfaces that you use to prepare food with hot, soapy water.
- Don’t serve unpasteurized milk or food that contains unpasteurized milk.
- Wash all raw vegetables and fruits that you can’t peel yourself.
- Keep raw foods (especially meat, poultry, and seafood) away from other foods until they’re cooked.
- Use perishable food or any food with an expiration date as soon as possible.
- Cook all food from animal sources to a safe internal temperature. For ground beef and pork, this means at least 160°F (71°C). For solid cuts of meat, the safe temperature is 145°F (63°C). For chicken and turkey (ground and whole), it’s at least 165°F (74°C). Cook chicken eggs until the yolk is firm. Fish generally is safe to eat once it reaches a temperature of 145°F (63°C).
- Refrigerate leftovers quickly, preferably in containers with lids that snap tightly shut.
- Defrost foods in the refrigerator, a microwave, or cold water. Food should never be thawed at room temperature.
- If food is past its expiration date, tastes funny, or smells strange, throw it out.
- If you’re pregnant, avoid all raw or undercooked meat or seafood, smoked seafood, raw eggs and products that might contain raw eggs, soft cheeses, unpasteurized milk and juice, patés, prepared salads, luncheon meats, and hot dogs.
- Don’t drink water from streams or untreated wells.
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
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