Food Poisoning (Foodborne Illness): Symptoms, the 16 Common Causes, and How to Recover Safely at Home
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: September 2026
Food poisoning (a type of foodborne illness) is a sickness caused by germs or other harmful substances — bacteria, viruses, parasites, toxins, or molds — in food or drink. Symptoms such as upset stomach, vomiting, diarrhea, cramps, and fever most often begin within hours or days of eating the contaminated food. Most people have mild illness that improves without treatment within 48 hours, with fluid replacement as the key home care. However, dehydration is the most common complication, and certain groups — infants and children, pregnant people, older adults, and those with weakened immune systems — face a higher risk of serious illness. Treatment is tailored to the cause, and strict kitchen hygiene plus safe food temperatures prevent most cases.
Quick Answer
What is food poisoning? A sickness caused by germs or harmful substances — bacteria, viruses, parasites, toxins, or molds — in food or drink.
What are the symptoms? Upset stomach, vomiting, loose stools (sometimes bloody), stomach pain and cramps, and fever; less often, nervous system symptoms like blurred vision, weakness, or tingling.
How fast do symptoms start? Usually within hours or days of eating the contaminated food, though some causes take up to 50 days.
What is the most common complication? Dehydration — a serious loss of water, salts, and minerals from vomiting and diarrhea; untreated, it can cause organ damage and death.
How is it treated? Most cases need no medicine; the priority is replacing fluids. Antibiotics, antiparasitics, or probiotics may be used depending on the cause, and adults without bloody stools or fever may use certain over-the-counter medicines.
How is it prevented? Washing hands for at least 20 seconds, separating raw foods, cooking to safe temperatures, refrigerating leftovers promptly, and throwing out anything in doubt.
What is food poisoning?
Food poisoning, a type of foodborne illness, is a sickness people get from something they ate or drank. The causes are germs or other harmful things in the food or drink. Food can be contaminated at any point from the farm or fishery to the table — during growing, harvesting or catching, processing, storing, shipping, or preparation.
A small point of terminology is worth noting. Many people use the term "food poisoning" for all foodborne illnesses. A health care professional may use the terms differently: foodborne illness applies to illnesses from any tainted food or drink, while food poisoning applies to illnesses from a toxin in food. Either way, the practical meaning is the same — a sickness traced back to something eaten or drunk.
Most people with food poisoning have mild illness and get better without treatment. But sometimes food poisoning causes serious illness or complications, which is why knowing the warning signs matters.
What do food poisoning symptoms look like?
Symptoms vary depending on what causes the illness, and they may begin within hours or weeks, depending on the cause. The common symptoms are upset stomach (general nausea and queasiness), vomiting (which can contribute to fluid loss), loose stools or diarrhea (sometimes bloody), stomach pain and cramps (which can be severe), and fever (a sign the body is fighting the illness).
Less often, food poisoning affects the nervous system. When it does, symptoms may include blurred or double vision, headache, tingling or numbness of the skin, weakness, and loss of movement in arms and legs, called paralysis. Nervous system symptoms always warrant prompt medical evaluation — especially since the source may be a toxin such as botulism.
When should you see a doctor?
The threshold for seeing a professional differs for children and adults.
Infants and children
Vomiting and loose stools can quickly cause low levels of body fluids, also called dehydration, in infants and children, and dehydration can cause serious illness in infants.
Call a health care professional if your child's symptoms include vomiting and loose stools along with any of the following: changes in how the child thinks or acts, unusual or intense thirst, little or no urination, weakness or dizziness, loose stools lasting more than a day, frequent vomiting, stools with blood or pus, severe pain in the stomach or rectum, any fever in children under 2, a fever of 102°F (38.9°C) or higher in older children, or a history of other medical problems.
Adults
See a health care professional or get emergency care if you have nervous system symptoms, such as blurry vision, muscle weakness, and skin tingling; changes in thinking or acting; a fever of 103°F (39.4°C) or higher; frequent vomiting; loose stools that last more than three days; or symptoms of dehydration — great thirst, dry mouth, little or no urination, and feeling weak, dizzy, or lightheaded.
What causes food poisoning?
Many germs or other harmful things in food or drink, called contaminants, can cause food poisoning. Food can be contaminated with bacteria, viruses, parasites that live in the intestines, harmful chemicals (toxins), bacteria that carry or make toxins, and molds that make toxins.
How food becomes tainted
Food can be tainted at any point from the farm or fishery to the table — during growing, harvesting or catching, processing, storing, shipping, or making the food. Anyone who handles food can taint it. Three behaviors drive most contamination: poor hand-washing (stool that stays on the hands after using the toilet can taint food), not cleaning cooking or eating areas (unwashed knives, cutting boards, or other kitchen tools spread contaminants), and poor storage (food left out too long at room temperature, or stored in a fridge or freezer that is too warm, can spoil).
Beyond the kitchen, swimming pools, lakes, ponds, rivers, and seawater can also carry bacteria that cause foodborne illnesses. And animals carrying bacteria such as E. coli may spread the disease through contact with people.
The 16 common causes
Common causes of foodborne illness include several bacteria, viruses, parasites, and toxins, each with its own timing and sources. Bacillus cereus (10 to 16 hours) comes from rice, leftovers, sauces, soups, and meats left out too long. Campylobacter (2 to 5 days) comes from undercooked poultry, shellfish, tainted water, and raw milk. Clostridium botulinum (18 to 36 hours) comes from honey given to infants, home-preserved foods, and store-bought canned foods or herb oils. Clostridium perfringens (6 to 24 hours) comes from meats, poultry, stews, and gravies not kept hot enough. Cyclospora cayetanensis (often 7 days) comes from produce tainted with stool carrying the parasite.
E. coli (most often 3 to 4 days, sometimes 1 to 10 days) comes from undercooked meat, unpasteurized milk or juice, and tainted water. Giardia lamblia (7 to 10 days) comes from food and water tainted with stools carrying the parasite. Hepatitis A (15 to 50 days) comes from raw shellfish, uncooked food, and water tainted with human stool. Listeria (9 to 48 hours for stomach issues, 2 to 6 weeks for body-wide issues) comes from hot dogs, luncheon meats, unpasteurized milk, and soft cheeses. Norovirus (12 to 48 hours) comes from shellfish, produce, and ready-to-eat foods touched by infected food handlers.
Rotavirus (18 to 36 hours) comes from food, water, or objects tainted with the virus. Salmonella (6 hours to 6 days) comes most often from undercooked poultry, eggs, and dairy from raw milk. Shellfish poisoning (most often 30 to 60 minutes, up to 24 hours) comes from shellfish tainted with toxins from coastal seawater. Shigella (1 to 4 days) comes from contact with a sick person or food tainted with human stool. Staphylococcus aureus (30 minutes to 8 hours) comes from meat, egg salad, potato salad, or cream-filled pastries left out too long. Vibrio (12 to 24 hours) comes from undercooked fish or shellfish, mainly oysters, and water tainted with sewage.
The timing matters: it is the main reason people can't always trace an illness to a specific meal. Because symptoms can appear hours, days, or even weeks after eating, other meals eaten in between often muddy the picture.
Who is at higher risk?
Anyone can get food poisoning. But some people are more likely to get sick or to have more serious illness or complications: infants and children (vomiting and diarrhea drain body fluids quickly, causing dehydration), pregnant people and their fetuses (some bacteria, such as listeria, can harm the pregnancy and newborn), older adults (reduced ability to replace lost fluids and fight infection), and people with weakened immune systems (another disease or treatments lower the body's defenses).
What are the possible complications?
Complications are not common for most healthy adults, but they can be serious.
Dehydration: the most common complication
Dehydration is a serious loss of water and salts and minerals, and both vomiting and loose stools cause it. Most healthy adults can drink enough fluids to prevent dehydration. Children, older adults, and people with weakened immune systems or other illnesses may not be able to replace the fluids they've lost, making them more likely to become dehydrated.
People who become dehydrated may need fluids directly into the bloodstream at the hospital (IV fluids). If not treated, serious dehydration can cause organ damage, other serious illness, and death.
Systemic (body-wide) infections
Some foodborne contaminants cause widespread disease in the body, called systemic disease — more common in older people, those with weakened immune systems, and those with other medical conditions. E. coli can cause blood clots that keep the kidneys from removing waste (hemolytic uremic syndrome, resulting in sudden kidney failure). Bacteria in the blood can cause illness in the blood itself or spread illness to other parts of the body. Meningitis is inflammation that may damage the membranes and fluid around the brain and spinal cord. Sepsis is when the immune system reacts too strongly to an illness, harming the body's own tissues.
Pregnancy complications
Illness from the listeria bacteria during pregnancy can result in miscarriage or stillbirth, sepsis in the newborn, and meningitis in the newborn.
Rare complications
Rare complications include conditions that may happen after food poisoning: arthritis (swelling, tenderness, or pain in joints), irritable bowel syndrome (an ongoing intestinal condition causing pain, cramping, and irregular bowel movements), Guillain-Barré syndrome (an immune system attack on nerves causing tingling, numbness, and loss of muscle control), and breathing troubles (rarely, botulism damages the nerves that control the muscles involved in breathing).
Can food poisoning be prevented?
Prevention at home centers on three areas: cleaning, safe preparation and storage, and special protection for at-risk groups.
Cleaning habits
Wash hands well with soap and water for at least 20 seconds — after using the toilet, before eating, and before and after handling food. Wash fruits and vegetables under running water before eating, peeling, or using in cooking. Wash cutting boards, knives, and other utensils with hot, soapy water after contact with raw meats or unwashed produce. Clean the inside of your fridge every few months with a solution of 1 tablespoon of baking soda per quart of water, and clean visible mold with 1 tablespoon of bleach per quart of water.
Preparing, eating, and storing safely
Keep raw meat, poultry, seafood, and eggs away from vegetables, fruits, and other foods, using separate cutting boards and fridge spaces. Thaw frozen food in the microwave, overnight in the fridge, or in a leakproof container in cold water, and reheat leftovers until the internal temperature reaches 165°F (74°C). Use a meat thermometer: whole meats and fish to at least 145°F (63°C) with a 3-minute rest, ground meat to at least 160°F (71°C), and whole and ground poultry to at least 165°F (74°C). Refrigerate or freeze leftovers in covered containers right after your meal — leftovers keep 3 to 4 days in the fridge. When in doubt, throw it out, even if a food looks and smells fine. Throw out moldy baked foods and soft fruits and vegetables, but mold can be trimmed from firm, low-moisture foods by cutting away at least 1 inch (2.5 cm) around the moldy part.
Extra protection for at-risk groups
For pregnant people, young children, older adults, and people with weakened immune systems, food poisoning may be life-threatening. These groups should avoid raw or undercooked meat, poultry, fish, and shellfish; raw or undercooked eggs and foods containing them (such as cookie dough); raw sprouts; unpasteurized juices and ciders; unpasteurized milk and milk products; certain soft cheeses (feta, brie, Camembert, blue-veined, unpasteurized); refrigerated pates and meat spreads; and uncooked hot dogs and deli meats.
How is food poisoning diagnosed?
A health care professional bases a diagnosis on a physical exam and a review of things that may be causing the vomiting, loose stools, or other symptoms. The review typically covers your symptoms, foods and drinks you've had recently, symptoms in people who ate with you, recent medicine changes, and recent travel. The exam serves two purposes: ruling out other causes of illness and checking for signs of dehydration. Stool sample tests find the bacteria, viruses, parasites, or toxins, while blood tests find a cause of illness, rule out other conditions, or find complications.
Pinpointing the exact contaminated food is often difficult. It can take hours or days to get sick, and during that time other meals are eaten, which makes it hard to find what food caused the illness. In a large outbreak, public health officials may be able to find the food that everyone affected shared.
How is food poisoning treated?
Treatment depends on how bad your symptoms are and what caused the illness. Most often, you don't need medicine at all.
Fluid replacement — fluids and electrolytes such as sodium, potassium, and calcium — keeps the body's fluid balance after vomiting or loose stools. Antibiotics are used for illness caused by bacteria, mainly in serious illness or higher complication risk. Antiparasitics target parasitic infections. Probiotics may be suggested to replace healthy bacteria in the belly. Adults with loose stools that aren't bloody and no fever may take over-the-counter loperamide (Imodium A-D), and bismuth subsalicylate (Pepto-Bismol, Kaopectate) can treat an upset stomach — neither is for children. IV fluids given through a vein are used in a hospital stay for serious dehydration.
Home care: how to recover within 48 hours
For most people, symptoms improve without treatment within 48 hours. The top priority is replacing lost fluids. Water, broth, or drinks that contain minerals called rehydration solutions all help. Talk with a health care professional before giving rehydration fluids to infants.
As you start to feel better, eating approaches vary. Some people stop eating until their stomach feels better and vomiting stops. Then low-fat foods can be sampled to see if they stay down: crackers, noodles, bananas, rice, boiled vegetables, soup, or oats. Yogurt might be fine, but other dairy products might cause an upset stomach.
How to prepare for your appointment
Start by seeing your main health care professional; sometimes you may need to see a specialist in infectious diseases. Being ready to answer a few questions helps the professional reach a diagnosis faster: when your symptoms began, whether they come and go or stay constant, whether you've had bloody or black/tarry stools, whether you've had a fever, what you've eaten lately, whether anyone else who ate the same food had symptoms, whether you've traveled recently, what medicines and supplements you take, and whether you took antibiotics or changed medicines before symptoms started.
Bottom line
Food poisoning is one of the most common medical experiences there is — a contaminated meal or sip of water can bring anyone down with nausea, vomiting, and diarrhea, usually within hours or days. The good news is equally clear: most cases are mild, need no medicine, and resolve within 48 hours with careful fluid replacement and a gentle return to low-fat foods.
What makes food poisoning worth taking seriously is not the typical case but the exceptions. Infants, children, pregnant people, older adults, and anyone with a weakened immune system can deteriorate quickly from dehydration. And when symptoms touch the nervous system — blurred vision, muscle weakness, tingling, or paralysis — the illness has moved beyond a simple stomach upset and demands prompt medical care.
Your next step: If you develop symptoms, start replacing fluids immediately — water, broth, or rehydration solutions. Watch for the warning signs above and seek care when they appear. Then prevent the next episode: wash hands for 20 seconds, separate raw foods from ready-to-eat ones, cook meat to verified safe temperatures, refrigerate leftovers promptly, and when in doubt, throw it out.
FAQ
What are the symptoms of food poisoning?
The common symptoms are upset stomach, vomiting, loose stools (sometimes bloody), stomach pain and cramps, and fever. They vary depending on what causes the illness and most often begin within hours or days of eating the contaminated food. Less often, food poisoning affects the nervous system, causing blurred or double vision, headache, tingling or numbness of the skin, weakness, or paralysis.
How long does food poisoning last?
For most people, symptoms improve without treatment within 48 hours. Some causes take much longer to appear — from 30 minutes (Staphylococcus aureus) to 50 days (hepatitis A) — and a few, such as listeria, can cause body-wide illness two to six weeks after exposure.
What is the most common complication?
Dehydration — a serious loss of water, salts, and minerals caused by vomiting and diarrhea — is the most common complication. Most healthy adults can replace lost fluids by drinking. Children, older adults, and people with weakened immune systems may not be able to, and untreated serious dehydration can cause organ damage and death.
How is food poisoning different from a food allergy?
Food poisoning comes from germs or harmful substances in the food, with symptoms starting within hours or days (sometimes longer) and usually including diarrhea and fever. A food allergy is an immune reaction to a food protein, with symptoms starting within minutes to two hours and including skin, breathing, and sometimes anaphylaxis symptoms.
How can I prevent food poisoning at home?
Wash hands with soap and water for at least 20 seconds; wash fruits and vegetables under running water; keep raw meat, poultry, seafood, and eggs separate from other foods; use a meat thermometer (145°F for whole meats and fish, 160°F for ground meat, 165°F for poultry); refrigerate leftovers in covered containers right away (good for 3 to 4 days); thaw food safely; and when in doubt, throw it out — even if it looks and smells fine.
Can food poisoning come back after I recover?
Rarely, complications can appear after the initial illness, including arthritis, irritable bowel syndrome, Guillain-Barré syndrome (tingling, numbness, and loss of muscle control), and — rarely with botulism — breathing troubles caused by nerve damage. These are uncommon and more likely in older adults and people with other health conditions.
References
This article is for general informational purposes and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional about any medical condition.
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