Reheated rice syndrome, or fried rice syndrome, is a type of food poisoning that happens when you eat rice left out too long after cooking. Bacteria known as Bacillus cereus (B. cereus) can grow on the rice and make toxins, which may cause nausea, vomiting, or diarrhea within hours of eating it.
The two main types of reheated rice syndrome are emetic (vomiting) and diarrheal. They both cause gastrointestinal symptoms. However, each type overall affects the body differently, with unique timeframes for when symptoms start after you’ve eaten the contaminated food.
Emetic Type
The emetic type involves a cereulide toxin. It triggers nausea and vomiting that come on fast, usually within 30 minutes to six hours after eating cooked rice left at room temperature for too long. This is the most commonly occurring type of food poisoning caused by starchy foods, especially rice.
Diarrheal Type
The diarrheal type involves enterotoxins. This type affects the lower part of your digestive system, such as the small intestines, so symptoms show up later compared to the emetic type. It causes abdominal (belly) cramping and watery diarrhea, typically about six to 15 hours after eating contaminated food.
Common symptoms of reheated rice syndrome include:
These symptoms tend to go away on their own within 24 hours.
Reheated rice syndrome happens when you eat food contaminated with B. cereus. This common bacterium lives in soil, dust, and raw foods like rice. Cooking usually kills it. However, B. cereus can leave behind tough spores that survive heat while cooking in the microwave, rice cooker, or on the stove.
Despite the name, reheated rice syndrome doesn’t begin when you reheat rice. It starts after first cooking and cooling the rice. If you leave cooked rice at room temperature for more than two hours, those spores can multiply and produce toxins.
Bacillus cereus can make two different toxins, and reheating won’t destroy either. These toxins can make you sick whether the rice is hot, cold, or lukewarm. The type of toxin depends on how long the food sat out and at what temperature. The cereulide toxin causes vomiting, while enterotoxins cause diarrhea.
Risk Factors
You’re more likely to get sick from B. cereus if you:
- Have a weakened immune system
- Leave cooked rice or pasta at room temperature for more than two hours
- Store food in large containers that take too long to cool
Doctors usually diagnose reheated rice syndrome by asking about your symptoms and what you recently ate. If your symptoms are mild and go away within 24 hours, you probably won’t need any testing.
Your doctor may order additional tests if:
- There’s concern about a larger outbreak or food contamination
- You have a fever or bloody diarrhea
- Your symptoms last longer than 24-48 hours
- You’re very young, an older adult, or have a weakened immune system
Because symptoms are similar to other foodborne illnesses, your doctor may also consider infections like norovirus, Escherichia coli (E. coli), or Salmonella. To help confirm the cause, they may order the following tests:
- Stool (poop) tests or cultures: These check for bacteria like Salmonella, E. coli, or Shigella, parasites, or viruses like norovirus or rotavirus.
- Vomit tests: These look for toxins or bacteria like Bacillus cereus.
- Blood tests: These check for dehydration or signs of infection.
If the rice is still available, they may test it using lab cultures and toxin detection to confirm the presence of B. cereus.
The goal of treatment is to relieve symptoms and prevent complications like dehydration. At-home care includes:
- Drinking plenty of clear fluids. If you’re nauseous or vomiting, try small sips every few minutes.
- Eating bland foods, like saltine crackers, once vomiting or diarrhea slows down
- Resting until you feel better
In severe cases, your doctor may recommend medications like Zofran (ondansetron) for nausea and vomiting and Imodium (loperamide) or Pepto-Bismol (bismuth subsalicylate) for diarrhea.
Call your doctor if you:
- Can’t keep fluids down
- Don’t start to feel better after 24 hours
- Have a fever
- Have blood in your vomit or stool
- Have signs of dehydration, such as dry mouth, dizziness, and less urine
To lower your risk of reheated rice syndrome:
- Avoid leaving cooked rice out at room temperature for more than two hours, or one hour if it’s hotter than 90 degrees Fahrenheit (32 degrees Celsius) outside.
- Keep cold foods cold, below 40 degrees Fahrenheit (four degrees Celsius)
- Keep hot foods hot, above 140 degrees Fahrenheit (60 degrees Celsius)
- Place rice in the refrigerator within 1-2 hours of cooking.
- Toss leftover rice if you’re unsure how long it’s been sitting out.
- Transfer rice to shallow containers after cooking to help it cool quickly.
Most people recover from reheated rice syndrome within 24 hours. However, in severe cases, especially if you have a weakened immune system, you may experience the following complications:
- Dehydration: This happens when your body loses too much fluid from vomiting or diarrhea. You might feel very thirsty, tired, dizzy, or notice dry mouth, less urine, or dark-colored urine.
- Electrolyte imbalances: This occurs when you lose minerals like sodium and potassium along with fluids. Electrolyte imbalances may cause fatigue, muscle cramps, weakness, or an irregular heartbeat.
- Hospitalization: In rare cases, where symptoms are severe or non-stop for long periods, you may need intravenous (IV) fluids, which are fluids given by vein, or monitoring.
Reheated rice syndrome is food poisoning from Bacillus cereus. It usually starts within hours after eating cooked rice that sits at room temperature for too long after cooking. Symptoms include vomiting, diarrhea, or stomach cramps and typically resolve in 24 hours. Most people recover quickly with rest and fluids. To reduce your risk, cool cooked rice in a shallow dish, refrigerate it within one hour of cooking, and throw it away if left out more than two hours.
