Food poisoning is a condition caused by consuming contaminated foods or beverages that contain harmful bacteria, viruses, or parasites. These organisms can multiply in the body, leading to illness. Common bacterial culprits include Salmonella, E. coli, and Listeria.

In industrialized nations like Canada, Japan, Australia, New Zealand, the United States, and many European countries, up to 30% of people experience food poisoning each year. Typical symptoms include nausea, vomiting, fever, and stomach cramps. Symptoms may begin just a few hours after consumption or may take up to a week to appear, lasting anywhere from one day to a week.

While most cases resolve on their own with rest and hydration, food poisoning can lead to dehydration, which may worsen symptoms and require medical attention.

Common Symptoms

Food poisoning leads to the release of toxins from bacteria, causing symptoms that resemble the stomach flu.

nausea
A frequent symptom, nausea can be intense enough to suppress appetite or make it difficult to drink fluids.

other symptoms

  • Diarrhea, sometimes with blood

  • Vomiting

  • Abdominal cramps or pain

  • Fever

  • Headache

in infants and children

  • Increased irritability or mood changes

  • Low energy levels

  • Diarrhea lasting more than 24 hours

  • Frequent vomiting or loose stools

Dehydration Symptoms

Dehydration is a common complication of food poisoning due to fluid loss from vomiting, diarrhea, and fever, or from not drinking enough fluids.

symptoms of dehydration

  • Intense thirst

  • Dry mouth and lips

  • Dry or cool skin

  • Reduced urination or sweating

  • Dark urine

  • Fatigue

  • Light-headedness or dizziness

Severe Symptoms

Some signs of food poisoning can indicate a more serious condition and require immediate medical attention.

severe food poisoning symptoms

  • Confusion or mental changes

  • Diarrhea more than six times in a day

  • Diarrhea lasting over three days

  • Inability to retain fluids

  • Severe stomach or rectal pain

  • Black or tarry stools

  • Fever above 102°F

severe dehydration symptoms

  • Rapid heartbeat or breathing

  • No urination

  • Confusion or disorientation

  • Fainting

Rare Neurological Symptoms

Some types of food poisoning involve toxins that affect the nervous system. Though rare, these conditions can be dangerous and even fatal.

One example is botulism, caused by a toxin produced by Clostridium botulinum, a bacterium commonly found in soil. Botulism can result from improperly canned foods, especially low-acid vegetables like green beans, beets, and potatoes.

early symptoms of botulism

  • Headache

  • Skin tingling or numbness

  • Muscle weakness

  • Blurred or double vision

  • Drooping eyelids (ptosis)

  • Slurred speech

  • Paralysis

These symptoms typically begin 18 to 36 hours after eating contaminated food. Medical treatment such as botulinum antitoxin is available, but early intervention is crucial.

Symptoms in Children

Children represent about 40% of food poisoning cases and are more vulnerable to serious illness due to underdeveloped immune systems.

common symptoms

  • Diarrhea

  • Nausea

  • Stomach pain

  • Vomiting

severe symptoms in children

  • High fever

  • Severe abdominal or rectal pain

  • Stools that are black or contain blood or pus

  • Headache or neurological complaints like blurred vision or numbness

signs of dehydration in children

  • Dry mouth or tongue

  • No tears when crying

  • Fewer wet diapers (none for 3 hours or more)

  • Drowsiness or lethargy

  • Irritability

  • Persistent fever

If these symptoms appear, it's important to seek medical care right away. Children under age five are three times more likely to require hospitalization for Salmonella food poisoning.

Infant Botulism

Infants can develop botulism from ingesting spores found in soil or honey, which is why honey should not be given to babies under one year old.

signs of infant botulism

  • Weak or altered cry

  • Limited facial expression

  • Constipation

  • Poor feeding

  • Pupils that react abnormally to light

  • Drooping eyelids

  • Trouble breathing

Immediate medical care is essential if these symptoms arise.

When To See a Healthcare Provider

Severe cases of food poisoning or dehydration may lead to hospitalization. Approximately 128,000 people are hospitalized annually due to complications from food poisoning.

You should contact a healthcare provider if:

  • You cannot keep food or fluids down for several days

  • You are pregnant and showing symptoms

  • A child under five or an adult over 65 has symptoms

  • You have a weakened immune system and develop symptoms

Early medical evaluation can help prevent complications and ensure proper recovery.

A Quick Review

Food poisoning symptoms can begin soon after eating contaminated food or may take several days to appear. While symptoms like vomiting, diarrhea, and nausea usually improve on their own, some people—particularly infants, the elderly, and immunocompromised individuals—may experience more severe complications.

Recognizing the signs of dehydration and neurological symptoms is critical, as these require urgent medical care. For most cases, staying hydrated and getting rest is key to recovery, but do not hesitate to seek medical attention if symptoms persist or worsen.