What Happens If You Accidentally Eat Mould

Mould is microscopic fungi that can grow on wood, paper, carpet, food, and building materials such as insulation. All moulds need water or moisture to grow. Wherever there is moisture and oxygen, mould can grow — and this includes your old mattress.

There are many, many species of fungi, with some estimates suggesting 300,000 or more, according to the United States Department of Agriculture (USDA). This is why the mould that pops up on your breakfast muffin may look different than the furry layer that grows on your lunch meats, explains Elena Ivanina, DO, gastroenterologist, Lenox Hill Hospital, New York City.

Unlike bacteria, moulds grow in structures that contain many cells, and you don’t need a microscope to see them. In general, moulds consist of root threads that run deep into food, a stalk that rises above the food and spores at the end of the stalks. Spores give mould its variety of colours and also help transport it from item to item.

“If you pick up a dandelion and blow on it, the seeds disperse in the air, and that’s how mould spores travel from place to place, contaminate products and cause spoilage,” says Robert Gravani, professor and director of the National Good Agricultural Practices Program, Cornell’s College of Agriculture and Life Sciences, Ithaca, New York.

“Moulds are nature’s decomposers. If you have a fruit with mould, eventually that fruit will be decomposed,” says Gravani. “Moulds are very efficient in what they do.”

Mould thrives in warm, humid environments, but that doesn’t mean it can’t also form and grow in your refrigerator. Moulds are pretty smart, too, and tolerate preservatives such as salt and sugar better than most other food invaders. “They are pretty hearty critters,” Gravani says.

The good and bad types of mould

Not all moulds are bad. In fact, some can be very beneficial. The life-saving antibiotic penicillin is made from Penicillium mould, Ivanina notes. Certain hard cheeses are also made from mould, she says.

Allergic reactions to mould

Some people are allergic to mould, says Ivanina. This is usually mould in the environment as opposed to food, but for these people, exposure to mould can cause vomiting, diarrhea, or headaches. If your doctor suspects a mould allergy is to blame, you will likely be referred for testing, she says.

Hidden patches of mould can lurk in all different areas of your home and may make you sick. “If you have an underlying health condition that affects your immune system, exposure to mould can be dangerous,” Ivanina says. “You may have a much worse reaction to eating mould than someone else because you don’t have a healthy immune system to fight that reaction.”

(Related: Simple Habits to Naturally Boost Your Immune System)

Some moulds produce poisonous substances

A few moulds produce mycotoxins or poisonous substances that can make you very sick. For example, moulds produced by the Aspergillus species can cause aflatoxicosis, a life-threatening form of acute poisoning with the potential to cause liver damage.

This type of mould tends to lurk in cereals, oilseeds (such as soybean, peanut, sunflower, and cotton seeds), spices, and tree nuts. These mycotoxins have been linked to cancer in animals and can cause liver cancer in humans. “Some are highly toxic, which can get you really sick or cause cancer,” says Gravani.

How to handle mouldy foods

When it comes to food, it can be tempting to cut away mould and eat it anyway, given the high price tags of certain products, but it’s usually not worth it, Gravani says.

Besides the risk of illness, mouldy food doesn’t taste great, he says. Most moulds on soft foods will taste like soil or dust. Tip: Never sniff the mould to make sure it’s mould, the USDA advises. If it looks like mould, it likely is mould, and smelling it can cause respiratory issues. When in doubt, throw it out, Ivanina says.

Cheese

There are different rules for cheese depending on its texture.

Hard cheese

Hard cheeses (not to be mistaken with those that have mould as part of the process) can be consumed if you cut off at least one-inch around and below the mould. Make sure to keep the knife away from the mould to avoid spreading it. Still, Gravani adds, “If the hard cheese is heavily encrusted with mould, I would probably discard it.”

Soft cheese

If you see mould on soft cheese such as cottage,  cream cheese, or all types of crumbled, shredded, and sliced cheeses, throw it out. These may be contaminated below the surface and can also have bacteria growing along with the mould.

Some cheeses are made with mould, including Roquefort, blue, Gorgonzola, Stilton, Brie, and Camembert. If they contain moulds that are not a part of the manufacturing process, these cheeses can be dangerous.

Texture is a good rule of thumb with these types of cheese as well. Discard soft cheeses if they contain moulds that are not a part of the manufacturing process, and cut surface mould off on hard cheeses such as Gorgonzola and Stilton.

(Related: Is It Healthy to Eat Cheese Every Day?)

Fruits and vegetables

Like cheese, there are different rules for fruits and vegetables based on the texture.

Soft produce

Discard soft fruits and veggies like cucumbers, peaches, and tomatoes if you spy any mould. Many of these may also be contaminated under the surface, says Ivanina.

What you see isn’t all that you get with moulds. “Root” threads from the molud tend to run deep, especially in foods that show heavy mould growth.

Firm produce

You can keep these if you cut out all the mould. This is due to the low moisture content is seen with firm fruits and veggies like cabbage, bell peppers, and carrots. With these types of foods, mould can’t penetrate them easily.

Luncheon meats, bacon, or hot dogs

The rule of thumb for these types of food is to discard. These may also be contaminated under the surface and could also harbour bacteria, Ivanina says.

Cooked casseroles and leftover meat and poultry

Get rid of these if you see mould as there is a good chance it runs deep and it may travel with bacteria. It’s also a smart idea to use or get rid of leftovers within three or four days.

Cooked grains and pasta

Like other leftovers, if you see mould on cooked grains or pasta, toss it. There is likely mould under the surface.

Yogurt and sour cream

If you see mould, get rid of yogurt and sour cream immediately. Mould is likely growing beneath the surface, and there’s a good chance that the mould is travelling with bacteria.

Jams and jellies

These should be trashed if you see any mould. These foods could be producing a mycotoxin if they develop mould, which is why microbiologists warn never to scoop out the mould and use the remains.

Bread and baked goods

Get rid of mouldy bread and baked goods, says Ivanina. “Mould can spread really fast on soft things like breads and muffins.”

Peanut butter, legumes, and nuts

Discard these because foods processed without preservatives are at high risk for mould.

How to avoid eating mould

Preventing mould from forming can go a long way toward preserving your food supply and eliminating waste. This starts by storing fruits and vegetables in individual plastic bags in your produce drawer.

Keep food covered when serving to prevent exposure to mould spores in the air, and use plastic wrap to cover foods you want to stay moist to keep mould away.

Don’t forget to always empty open cans of perishable foods into clean containers and refrigerate them right away. And never leave any perishables out of the refrigerator for more than two hours.

Clean out your refrigerator and bread drawer often, Gravani says. Also, as a rule of thumb: “Toss out the food when you spot mould as it will travel and invade the rest of your food, too.”

Next: 11 Cooking Mistakes That Can Make Your Food Toxic