How to Know if the Pizza You Left Out Has Gone Bad

Many times, we can forget to put something in the refrigerator before going to bed, but leaving food out can lead to serious consequences. What about pizza?

According to the USDA, it is unsafe to eat pizza after leaving it out for longer than 2 hours. The average person, however, will eat pizza the next day if it has been left out of the refrigerator. When pizza starts to smell or taste bad, people will throw pizza out because it is no longer desirable.

There are many types of perishable foods, and when they are not prepared or kept correctly, they can potentially make people seriously ill. By following rules set by the USDA, a person can stay safe and healthy.

Is Pizza a Perishable Food?

Perishable foods are any foods that need to be refrigerated to be safe for consumption. These types of foods need to be kept at cool temperatures because they will spoil quickly and easily. When perishable foods are not kept in the refrigerator, bacteria can spread quickly and the USDA deems them unsafe for consumption.

If perishable foods are kept in the refrigerator at a temperature lower than 40°F, they will last much longer than if they are left out. Milk, for example, can still be consumed after the sell-by date if it is refrigerated.

According to these qualifications, pizza is a perishable food. Pizza contains ingredients like milk, which is a big factor in it being perishable. It definitely should be kept in the refrigerator, but most people may not put the pizza in the refrigerator.

Meat is also a food that needs to be refrigerated because it will go bad more quickly when it is left out, so if the pizza has meat toppings on it, it needs to be refrigerated.

If you are unsure whether or not something is safe to eat, you can always rely on your senses. If something does not smell good or taste good, it is safe to say you should probably not eat it.

Often bad food has a rancid smell. When the food does not smell like it once did and is beginning to stink, it is a good idea to throw it out.

And if you happen to be a gardener, hold up for just a bit. I wrote an article all about how and why to compost your old pizza crust that I encourage you to read!

A Realistic Amount of Time to Leave out Pizza

It is mainly up to personal preference regarding how long you want to leave pizza out. The USDA does say that any perishable food that has been left out for two hours or more is no longer safe to eat, but I personally know people who will eat pizza after it has been left out for days at a time. My family makes the choice to refrigerate it, but it is mostly up to personal preference.

My parents always taught us to keep the pizza in the fridge because they were very cautious regarding the bacteria that can grow on pizza. Bacteria do have a higher risk of entering your body if you do not refrigerate pizza.

It’s also a good idea to wrap up the pizza instead of just setting it out. You’ve probably seen vegetables and cheese that have mold on them, even in the fridge. So, wrapping your slices up can help it stay edible for longer.

Bacteria that Can Spread on Pizza That Has Been Left Out

The USDA has publicly come out and said that eating perishable foods that have been left out overnight are not safe to eat. This includes pizza because it’s ingredients, such as cheese, are dairy-based. Eating foods like this can make a person develop food poisoning because of the bacteria that spread on it.

Food can be contaminated in all sorts of ways and can make a person sick. Each bacteria affects the body differently, though. Some of these bacterias include salmonella, staph aureus, norovirus, just to name a few.

Staph Aureus

When perishable food is left out of the fridge, a bacteria called Staph aureus will contaminate the food. Staph aureus is a type of bacteria that is on the skin. When a person does not wash their hands before handling food, it can make others deeply ill. A person can develop food poisoning or something even worse called sepsis. The way to prevent this is to be clean when it comes to working with food, as well as not eating perishable foods that have been left out.


Sepsis is when an infection takes over the body. When chemicals that are released in the bloodstream try to fight an infection, the body can react negatively and can trigger inflammation in the body. This can be as serious as death.


Norovirus is a bacteria that happens to be one of the leading causes of food poisoning. When someone gets norovirus, it is because someone who is sick has prepared food. The way to prevent norovirus is to not prepare food while you are sick and maintain a clean workspace, washing dishes, and utensils you use regularly.

It is important to know that bacteria can enter your body through food, especially something as simple as pizza. Pizza can accumulate all sorts of bacteria when it is left out, just like any food that has been left out can.

It’s also important to know that bacteria will affect children and immune-compromised people more than others, and can be very serious.

How to Know When Pizza Goes Bad

A person can stay healthy if they follow the advice given by the USDA regarding food safety. The USDA, for example, suggests that people do not eat perishable foods that have been left out in a room temperature environment for 2 hours or longer.

By this time, bacteria have started to grow and still has the chance of making an individual sick.

So, if the pizza has been sitting out overnight, even zapping it in the microwave won’t make it safe to eat. If you are willing to take your chances, just know that there is a shot that you can become sick.

Pizza can go bad even if you did not leave it out. According to the USDA, pizza will generally stay good for 4 days after it is made if it is kept in the refrigerator at a temperature lower than 40°F. You will know your pizza has gone bad, though, if the pizza has a hard and dry texture. The leftovers may even begin to grow mold.

The mold will not necessarily make you sick, but if a person is allergic, they may have an allergic reaction. Other kinds of mold can be poisonous, though. It is good to be safe and not partake of food that is moldy.

It is not safe to eat pizza that has been left out because it can make you ill. Sometimes people will have a lesser consquence for eating pizza that has gone bad, but it is always good to be safe.

Anna Silver

Anna Silver is the principal creator of, a website dedicated to new go-to original recipes. Inspired by her grandmother’s love of cooking, Anna has a passion for treating the people in her life to delicious homemade food and loves to share her family recipes with the rest of the world.

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