Should You Be Worried if You Eat Bad Cheese? Experts Explain

Article By Korin Miller Published Aggust 8, 2025
Article Source: https://www.prevention.com/food-nutrition/healthy-eating/a65637767/eat-bad-cheese/

It's easy to buy a tasty wedge of cheese or a fresh head of lettuce, use it once, and then forget about it for days or more. Then when you do reach into the back of your fridge and pull it out, that cheese might be speckled with patches of mold.

About the experts: Darin Detwiler, LP.D., director of the Regulatory Affairs of Food and Food Industries program at Northeastern University and author of Food Safety: Past, Present, and Predictions; Susan Whittier, Ph.D., the former director of the clinical microbiology service at New York Presbyterian/Columbia University Medical Center, now retired; Jane Ziegler, D.C.N., R.D., L.D.N., a professor and director of the Department of Clinical and Preventive Nutrition Sciences at Rutgers University.

So what do you do? Cut off the mold and eat the bad cheese? Toss it in the garbage and add it to your grocery list? Or worse, what happens if you eat bad cheese before you notice that there's something growing on it? Here are the answers to all these questions, plus tips on how to store your cheese to keep it fresher and tastier for longer.

How mold grows on food

Mold is a type of microscopic fungus that thrives in damp areas, according to the USDA Food Safety and Inspection Service. It’s unclear exactly how many different types of mold there are, but there may be 300,000 or more.

Most molds are threadlike, multi-celled organisms that are transported by water, air, or insects, per the USDA. Many have a body that consists of root threads that invade the food it lives on, a stalk that rises above the food, and spores that form at the ends of the stalks.

Foods that are moldy can also have invisible, harmful bacteria like Listeria, Salmonella, and E. coli growing along with them, said Darin Detwiler, LP.D., director of the Regulatory Affairs of Food and Food Industries program at Northeastern University and author of Food Safety: Past, Present, and Predictions.

Keep in mind that you can’t necessarily see all of the mold that’s infected your cheese (or any other food). “Think of mold as a weed,” said Susan Whittier, Ph.D., the former director of the clinical microbiology service at New York Presbyterian/Columbia University Medical Center, now retired. “Even though you pull it out, it still has roots and it’s just going to grow back.”

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The type of food matters here, she said. Mold may be more likely to spread widely in soft foods, ruining even the parts that look OK, while it may be more localized in dense, hard foods, like Parmesan cheese.

How mold can make you sick

Again, there is a wide range of molds out there. Some will do nothing, while others can make you really sick. Certain molds can cause allergic reactions and respiratory problems, according to the USDA. And some molds, with the right conditions, can produce something called “mycotoxins,” which are poisonous substances that can make you sick and even kill you. The good news when it comes to cheese, however, is that mycotoxins typically grow in grains, nuts, and produce, not dairy products.

How cheese gets moldy

Some cheeses are meant to be moldy, and it’s OK to eat those molds, said

Jane Ziegler, D.C.N., R.D., L.D.N., a professor and director of the Department of Clinical and Preventive Nutrition Sciences at Rutgers University.

“Blue veined cheese—Roquefort, blue, Gorgonzola, and Stilton—are formed by the introduction of Penicillium roqueforti spores,” she explained. “Brie and Camembert have white surface molds. Other cheeses may have an internal and a surface mold. These cheeses are safe to eat.”

But mold spores that aren't meant to be there can also latch onto your cheese through the air or water, where they can grow. “When moisture exists on any food, ventilation allows for exposure to spores, which can collect and grow on the food’s surface,” Detwiler said. “Mostly these are invisible to the naked eye, but when one can see mold, strong roots have already grown.”

What happens if you eat bad cheese

There’s a wide range here and a lot depends on the type of mold and whether it’s harboring bacteria—things you really can’t tell simply by eyeballing it. If you do eat bad cheese, just sit tight. Detwiler said that the best-case scenario would be that nothing happens—the cheese might taste bad or you may get a mildly upset stomach. Beyond that, the next scenario would be that you could have a moderate allergic reaction, contract a foodborne illness, or have respiratory issues. If there's bacteria in the cheese or it has released mycotoxins, you could be at risk of getting seriously sick, though Detwiler said that this is more of a risk for people who are immunocompromised.

What to do if you notice mold

“To be safe, it is better to toss the cheese, especially when there are children and individuals at high-risk in the household,” Ziegler said. That’s especially true when you’re dealing with a soft cheese, shredded cheese, or sliced cheese. “Because soft cheeses have a high moisture content, they can be contaminated well beyond the surface of the moldy area,” Ziegler added.

If your cheese is hard or semi-soft, like cheddar, Parmesan, or Swiss, Detwiler said you might be OK to cut off the moldy part and eat the rest of the cheese. “Cut off at least one inch around and below the moldy spot,” he said. “Be sure to keep the knife out of the mold, so it doesn’t contaminate other parts of the cheese.”

The best way to store your cheese to keep it fresh

The USDA specifically recommends cleaning the inside of your refrigerator every few months with either baking soda dissolved in water or a bleach solution to try to get rid of mold spores that could be lurking in there.

You’ll also want to keep your cheese covered in plastic wrap, and make sure you don’t leave it out of the fridge for more than two hours at a time, per the USDA. If you want to be really next-level about your cheese storage, you can try this tip from Detwiler: Wrap a hard or soft cheese in a new piece of parchment or waxed paper after each use to keep it fresh. “These breathable materials prevent mold-causing moisture from collecting on the surface without drying it out,” he said.

Bottom line: If you have moldy cheese and you’re not sure what kind it is or what to do, it’s really best to pitch it. If in doubt, throw it out.