Hungry mornings are the worst, especially if you had a blast the night before. 

Picture a tasty slice of pizza that you accidentally left out overnight. It wouldn’t hurt to grab a quick bite, would it? Take it from me. Please don’t touch that pizza unless it’s to toss it in the trash! 

The Two-Hour Rule for Pizza 

Pizzas of all kinds come packed with delicious ingredients that make them irresistible to almost everybody. These include different cheeses, meats, sauces and toppings. 

These ingredients also make pizza extremely perishable. Perishable foods are foods that go bad very quickly. You have to store them at cold temperatures to prevent them from spoiling. 

To be safe, you should follow the well-known 2-hour rule when handling pizza. It means that you can only leave out your pizza for two hours before you have put it in the refrigerator. 

It’s important to remember this rule because pizza still smells amazing after two hours of being left out. It can also look, taste and smell good after being left out overnight. 

Still, a pizza’s great appearance, taste or smell is not enough to ensure that it’s safe for you. This is because of kinds of bacteria known as pathogenic bacteria, which are disease-causing but are also tasteless, odorless and invisible. 

Pathogenic bacteria grows rapidly at room temperature. Your pizza may look, taste and smell fine, but if you’d left it out overnight, the chances of you getting sick after eating it are quite high because of such bacteria. 

Due to preservatives, fast food pizza goes bad slower than homemade pizza. However, you still have to follow the 2-hour rule for both kinds of pizza. 

It goes without saying that if the look, taste or smell of your pizza is a bit unusual, you should steer clear! Spoilage bacteria are not as harmful but they can make your pizza taste terrible. 

Another useful standard is the 2-hour rule/4-hour rule that’s used in the food service industry. Following this rule, you can put your pizza back in the refrigerator to be eaten later if you’ve left it out for less than two hours. If you leave it out for more than two hours, it’s still okay to eat, but it should not be refrigerated to be eaten later. If you’ve left it out for more than four hours, then you have to throw it away immediately. 

What Science Says About Leaving Out Pizza Overnight

Think your pizza looks fine to eat? Think again. Studies by the United States Department of Agriculture (USDA) show that leaving food at room temperature fosters the growth of illness-causing bacteria. The temperature at which this growth happens ranges from 40°F to 140°F. This range of temperatures is commonly known as the ‘Danger Zone.’ Shockingly, within the Danger Zone, the number of bacteria can double in as little as 20 minutes. 

These bacteria include Staphylococcus aureus, Salmonella Enteritidis, Escherichia coli O157:H7 and Campylobacter. Together, these are responsible for the vast majority of food poisoning cases.

As shown in the video above, a lot of these dangerous bacteria come from handling the pizza. When you have a pizza party, lots of people touch other slices when they are trying to grab a slice. This handling is the main source of bacteria that remains on a pizza left out overnight. Even if you ate a pizza on your own, bacteria from handling would still be present because your  hands definitely have a few of them. 

These bacteria are everywhere! Throughout the centuries, we’ve learned how to deal with them through proper food preparation practices that keep the food out of the ‘Danger Zone’ range of temperatures. These practices prevent them from multiplying to dangerous levels. You can either refrigerate your pizza to keep it below 40°F. You can also keep it hot to keep it above 140°F. 

Having said that, reheating a pizza you left out overnight won’t make it safe to eat. If you didn’t keep your pizza out of the ‘Danger Zone’ throughout the night, the invisible, odorless and tasteless bacteria already had their way! In fact, reheating a pizza you left out overnight may give some of these bacteria the ideal temperature to multiply even more. 

Wash your hands before handling the pizza. If this is a homemade pizza, wash your utensils and food preparation surfaces before preparing it. Even if you do everything right, these bacteria will still be present. The key is to keep them below dangerous levels. This is easily accomplished if you take precautions. 

Did That Left Out Pizza Make You Sick?

Uh-oh. You are feeling queasy and don’t know what to do. You think it might be the pizza you left out overnight and then ate in the morning. Let’s look into it together! 

Food poisoning cases range from quite mild to very serious and even life threatening. If after eating that pizza, you suffer from a high fever or dehydration for more than 24 hours, you need to see a doctor immediately.

Luckily, most food poisoning is not that serious. You may have to miss a few days of work, but that’s it. However, if you have a weakened immune system, you may suffer more complications. 

Bacterial food poisoning can happen to you in the form of bacillus cereus, listeria, salmonella, staphylococcus aureus, to mention a few. Usually, the names of the bacteria are the same as the sickness they cause. 

Bacillus cereus commonly exists in our environment and can survive the heat of the normal pizza preparation process because it is heat resistant. Then, once in room temperature or in the ‘danger zone’ of 40°F to 140°F, bacillus cereus multiplies rapidly. You need to keep your pizza warm or cool it rapidly to prevent bacillus cereus food poisoning. You cannot leave it out overnight. Bacillus cereus food poisoning will make you suffer from vomiting, abdominal pain or diarrhea. Make sure to get plenty of rest and drink lots of fluids. If symptoms persist for more than 24 hours, see a doctor. 

Listeria monocytogenes causes listeriosis. Although mild for most people, listeria food poisoning can cause serious complications for pregnant women, newborns, the elderly and people with weakened immune systems. This type of listeria is called invasive listeriosis. It can be treated with antibiotics. To prevent listeria food poisoning, keep your pizza out of the ‘danger zone’ of temperatures. 

Salmonella bacteria is the most common cause of food poisoning in the United States. It is also usually associated with high protein foods such as meat and poultry, which are often found on pizza. It will give you symptoms similar to a stomach flu. Salmonella is quite treatable.

How To Keep Your Left Out Pizza Safe 

If you are preparing your pizza at home, be sure to wash and sanitize your hands, surfaces and ingredients. If you are ordering in, choose a reputable restaurant that has a good health valuation and good reviews. You can check this information online before your purchase. 

If you are leaving your pizza on the counter for a few hours, simply close the box. This will protect it from your pets, as well as pests and insects. 

If possible, keep your pizza warm by putting it in the oven. You can always take it out if you’d like another slice. 

Wrap your pizza slices in aluminum foil to keep the pizza hot. This is a great option if you’d like to grab a bite on the go. 

Another great thing you can do is set your kitchen timer or phone timer to two hours. The timer will remind you to put your pizza in the fridge. 

How To Store Your Pizza Overnight 

If you’d like to enjoy your pizza past the two-hour limit, there’s a lot you can do! The easiest way to keep your pizza safe is through refrigeration. 

Refrigeration keeps it out of the temperature danger zone and limits the growth of bacteria. Store it in an airtight container like Tupperware and put it in the fridge. You’ll be able to enjoy your pizza for up to four days. Just take it out and reheat it using either the microwave or oven. 

Another failsafe method is to freeze your pizza slices. Use either an airtight container or a sealable freezer bag to store your pizza slices before freezing them. 

Freezing your pizza ensures that your pizza will be good to eat for up to three months. Allow your pizza to thaw in the fridge, on the counter, or in a bowl of cold or hot water before reheating it in the microwave or oven. 

Wrapping Up 

What’s your favorite kind of pizza? It would be difficult to come across a person who doesn’t love pizza, for good reason.  

Pizza is a versatile snack that is tasty and easy to prepare. If you made or ordered a huge pizza that you can’t finish, worry not. 

Follow these tips to make sure that it’s good to eat for the next few days (or weeks or months)! Whatever you do, don’t eat the pizza you left out overnight!