Food Safety

What Is Fried Rice Syndrome?

What Is Fried Rice Syndrome?
Lauri Patterson/iStock; Everyday Health
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Published on February 10, 2025
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Some cooked foods can become contaminated with dangerous levels of toxic bacteria if left out at room temperature for a few hours — even if the foods are then stored in the fridge and later reheated.

This is true of rice, which can lead to a type of food poisoning called “fried rice syndrome.”

Here’s what to know about the symptoms, causes, and treatments for fried rice syndrome, and expert advice on how to reduce your risk.

Overview

What Is Fried Rice Syndrome?

Fried rice syndrome describes a particular type of food poisoning caused by the bacterium Bacillus cereus.

The term “fried rice syndrome” originated in 1971 from the first reported case of B. cereus contamination at a Chinese restaurant.

B. cereus especially thrives on starchy foods, such as rice, pasta, potatoes, and pastries, although it can contaminate a range of foods, including cooked meats and vegetables, milk products, puddings, and soups.

“Bacillus cereus exists commonly in the environment [in the soil] but doesn’t cause problems until it has a starchy meal to grow on and has temperature-right conditions to help it multiply,” says Jeff Druck, MD, who works in the department of emergency medicine at the University of Utah School of Medicine in Salt Lake City. “If fried rice is left out at room temperature for a while, Bacillus cereus can multiply to levels that can cause people to get sick.”

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Symptoms of Fried Rice Syndrome

There are two types of food poisoning caused by B. cereus: enterotoxin and emetic.

With the enterotoxin form, the body produces B. cereus in the small intestines, which can lead to diarrhea.

With the emetic form, the toxin has already formed in your food before you eat it, and vomiting is the main symptom. This is the type of B. cereus food poisoning most closely associated with rice.

It’s possible, though, to experience both vomiting and diarrhea with fried rice syndrome.

“In med school, we remember Bacillus cereus as being so serious that you could have material coming out both ends,” says Dr. Druck.

Other symptoms of fried rice syndrome include:

  • Fever
  • Nausea
  • Stomach pain and cramping

The symptoms are very similar to illness from norovirus, the leading cause of foodborne illness, but are more likely to indicate fried rice syndrome if they appear shortly after eating contaminated food, according to Arun Swaminath, MD, chief of the gastroenterology division at Lenox Hill Hospital in New York City and a spokesperson for the American Gastroenterological Association.

Symptoms of fried rice syndrome typically start a half hour to six hours after eating the contaminated food, while norovirus infection typically causes symptoms 12 to 48 hours after exposure.

Most people with fried rice syndrome stop experiencing symptoms within 24 hours and fully recover within a few days.

Causes and Risk Factors of Fried Rice Syndrome

Low levels of B. cereus bacteria are generally harmless, but spores can rapidly multiply on cooked rice and other starchy foods that have been left on a countertop or stove top at room temperature, becoming dangerous within a few hours.

“These bacteria can exist in other foods, but there is something in warm and wet rice cooling to room temperature that creates a perfect scenario for this bacteria to grow and multiply,” says Dr. Swaminath

Research has shown that toxic spores in this setting can double in as little as 20 minutes.

Fried rice syndrome is also called reheated rice syndrome, underscoring the fact that heat may not kill B. cereus, as the bacteria can form spores that allow it to survive longer in temperature extremes. In this way, B. cereus is unlike other common foodborne bacteria such as salmonella and E. Coli, which die when exposed to high heat.

How Is Fried Rice Syndrome Diagnosed?

To confirm that an illness is due to B. cereus, a healthcare provider may test a sample of the food you ate, as well as a sample of your stool or vomit.

In some cases, a physician may order a blood test to look for signs of the toxin.

Testing for fried rice syndrome is not routine, however, since people typically get better on their own fairly quickly.

Treatment and Medication Options for Fried Rice Syndrome

There is no specific treatment for fried rice syndrome. Most people fully recover by getting plenty of rest and drinking lots of water.

Don’t take medications intended to stop diarrhea unless advised by a doctor, as these drugs may prevent the body from getting rid of toxins and prolong the sickness.

Some people who are vulnerable to complications from bacterial illness, such as children or those with underlying conditions or weakened immune system, may require medical attention.

Seek help if you experience:

  • Diarrhea that fails to get better over time (generally in two to three days)
  • Fever over 100.4 degrees F
  • Signs of dehydration, such as lightheadedness, dizziness, weakness, confusion, dry mouth and tongue, not urinating or sunken eyes

If symptoms are very serious, Swaminath notes that a healthcare provider may prescribe an antibiotic such as vancomycin, gentamicin, chloramphenicol, and carbapenems.

“These are only going to be given to a real minority of people who have a more complicated course of illness, and are probably ending up in an ER or admitted to the hospital for further care,” he says.

Complications of Fried Rice Syndrome

In very rare cases, people can suffer severe complications from intestinal B. cereus infections.

In 2008, a 20-year-old man became sick after eating a meal of leftover spaghetti with tomato sauce, which had been prepared five days before and left in the kitchen at room temperature. After experiencing headache, abdominal pain, nausea, and profuse vomiting, the young man died the next day.

How to Prevent Fried Rice Syndrome

To keep B. cereus bacteria from growing to harmful levels, the U.S. Department of Agriculture recommends refrigerating perishable food at 40 degrees F or below within two hours after cooking.

While refrigeration significantly slows down the growth of the bacteria, it does not completely stop it. In general, food safety experts recommend not keeping cooked rice and similar starchy food in the refrigerator any longer than one day, when the bacteria count may start creeping to unhealthy levels.

The Cleveland Clinic offers these tips on how to prevent fried rice syndrome:

  • Store after shopping. Keep uncooked rice and pasta in a cool, dry place until ready to cook.
  • Wash up. Wash your hands with soap and water before handling food.
  • Cook completely. Thoroughly cook your rice or pasta using boiling water or a rice cooker.
  • Cool quickly. Don’t leave any cooked food out for more than two hours. Transfer leftovers into containers and immediately place them in the fridge.
  • Reheat leftovers carefully. Reheat leftovers to 165 degrees F all the way through, and only reheat food once.
  • Toss. If it’s been more than two days since you cooked the food, toss it — even if you properly stored it in the fridge. When in doubt, throw it out.

The Takeaway

  • Fried rice syndrome is a type of food poisoning tied to reheated rice that can cause vomiting, diarrhea, or both.
  • Cooked rice and other starchy foods left out at room temperature for a few hours can provide a perfect environment for harmful bacteria to grow.
  • Symptoms of fried rice syndrome usually go away on their own after 24 hours, but people prone to complications from bacterial infections may require medical care.
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Yuying Luo, MD

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Yuying Luo, MD, is an assistant professor of medicine at Mount Sinai West and Morningside in New York City. She aims to deliver evidence-based, patient-centered, and holistic care for her patients.

Her clinical and research focus includes patients with disorders of gut-brain interaction such as irritable bowel syndrome and functional dyspepsia; patients with lower gastrointestinal motility (constipation) disorders and defecatory and anorectal disorders (such as dyssynergic defecation); and women’s gastrointestinal health.

She graduated from Harvard with a bachelor's degree in molecular and cellular biology and received her MD from the NYU Grossman School of Medicine. She completed her residency in internal medicine at the Icahn School of Medicine at Mount Sinai, where she was also chief resident. She completed her gastroenterology fellowship at Mount Sinai Hospital and was also chief fellow.

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Resources
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