Signs You Might Have Food Poisoning

Woman sitting on bed holding stomach, head bowed
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The symptoms of food poisoning can vary depending on what sort you might be dealing with, but there are definitely some characteristic signs that show up in most cases. If you think you have food poisoning it's important to see a doctor. If left untreated, a severe case of food poisoning could be fatal especially in the young, elderly, pregnant, or chronically ill.

Food Poisoning or Flu?

You might wonder whether the symptoms you're experiencing are really signs of food poisoning, or whether it's merely some sort of stomach flu or stomach bug. The terms “stomach flu” or “stomach bug” are just expressions used to describe symptoms that can be caused by food poisoning or an illness.

For that reason, looking at symptoms isn't always enough to diagnose a case of food poisoning. You might also want to think about what you recently ate and where you ate it. If someone else who ate the same food also has the same symptoms, that's a strong indicator of a case of food poisoning. If you are able to identify what food caused your illness it's important that no one else consume it or they could get sick as well.

Restaurants take foodborne illnesses very seriously and take many precautions to prevent them. If you're sure you got food poisoning from a restaurant, that could be a major public health hazard and it would be important for the local health department to know about it.

signs of food poisoning illustration
Illustration: Katie Kerpel. © The Spruce, 2019

Symptoms of Food Poisoning

While there are many bacteria that cause food poisoning, deducing which specific bug is causing your troubles can be much harder.  For example, Salmonella poisoning, one of the most common types of food poisoning in America, presents itself with abdominal cramps, headache, nausea, fever, diarrhea, and vomiting. These symptoms are quite general and are likely to be present in pretty much every form of food poisoning you can think of.

Vomiting

Vomiting is one of the most common signs of food poisoning. This makes sense because if you ate something bad, your body is going to try to get it out.

Vomiting is one of the signs of food poisoning caused by the following bacteria:

  • Salmonella
  • Shigella
  • Listeria
  • Campylobacter jejuni
  • E. coli

Diarrhea

Diarrhea is another common food poisoning symptom, and it's characteristic of the following bacteria:

  • Salmonella
  • Shigella (diarrhea could be bloody)
  • Listeria
  • Staphylococcus aureus
  • Clostridium perfringens
  • Campylobacter jejuni (diarrhea can be watery or bloody)
  • E. coli (watery, can turn bloody)

Headaches

A headache can be a sign of food poisoning. Usually, it will occur in combination with some of the other symptoms described here. A headache can be present in food poisoning caused by these bugs:

  • Salmonella
  • Listeria
  • Staphylococcus aureus (in severe cases)
  • Clostridium perfringens
  • Campylobacter jejuni

Abdominal Pain/Abdominal Cramping

There's a pretty fine distinction to be made here, as it may not be so easy to isolate abdominal pain caused by cramping from some other type of abdominal pain. Nevertheless, this can be a symptom of the foodborne illnesses below:

  • Salmonella
  • Shigella
  • Staphylococcus aureus
  • Clostridium perfringens
  • Campylobacter jejuni
  • E. coli (pain is severe)

Nausea

Another very basic symptom and not so easy to quantify, nausea can range anywhere from mild queasiness to vomiting and severe abdominal cramping. Like a headache, it will likely present itself in conjunction with some of the other symptoms listed here. Nausea is among the signs of these kinds of food poisoning:

  • Salmonella
  • Shigella
  • Listeria
  • Staphylococcus aureus
  • Clostridium perfringens
  • Campylobacter jejuni

Fever

Because the bacteria that transmit the illness are generally (but not always) causing an infection, one of the most common symptoms of food poisoning is a fever, as seen in the cases caused by these bacteria:

  • Salmonella
  • Shigella
  • Listeria (fever can be quite persistent)
  • Campylobacter jejuni
  • E. coli (sometimes; can be mild)

Dehydration

Dehydration can be caused by vomiting and diarrhea, so it's another symptom that's difficult to distinguish on its own. Still, you may experience dehydration when suffering from any of these forms of food poisoning:

  • Salmonella (particularly in very young or very old people)
  • Shigella
  • Clostridium perfringens

Muscle Pain or Cramping

Another reason people sometimes mistake food poisoning for the flu is that the flu can cause muscle aches, and so can some forms of food poisoning, including:

  • Listeria (a backache)
  • Staphylococcus aureus

Botulism: A Special Case

Botulism is one of the most deadly forms of food poisoning, and it's caused by bacteria that lives in an oxygen-free or low-oxygen environment. This makes it different from other foodborne pathogens. Botulism also presents its own unique set of symptoms. Botulism symptoms include:

  • Fatigue/weakness
  • Dizziness
  • Double vision or blurred vision
  • Dry mouth
  • Difficulty swallowing or speaking
  • Paralysis (in extremely advanced cases)
Article Sources
The Spruce Eats uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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