Moldy Foods: Why You Should Never Ignore Them

Mold is a type of fungus that grows on food when conditions are warm and moist. While some molds are intentionally used to make foods such as certain cheeses, unwanted mold on everyday foods can produce harmful substances called mycotoxins. Some of these toxins have been linked to food poisoning and, with long-term exposure, an increased risk of certain health problems.

Here are 10 important facts everyone should know about moldy foods.

1. Some Molds Produce Harmful Mycotoxins

Certain molds produce mycotoxins, toxic compounds that are invisible to the naked eye.

One of the best-known is aflatoxin, which can contaminate crops such as:

• Peanuts

• Corn

• Tree nuts

• Rice

• Wheat

• Spices

Long-term exposure to high levels of aflatoxins has been associated with an increased risk of liver cancer, particularly in areas where food storage conditions are poor.

2. Mold Can Spread Beyond What You See

The fuzzy spot on the surface is often only a small part of the mold.

Tiny root-like structures can spread deep into soft foods, meaning the contamination may extend far beyond the visible mold.

Simply scraping off the mold is often not enough.

3. Soft Foods Should Be Thrown Away

If these foods become moldy, they should generally be discarded:

• Bread

• Cooked rice

• Yogurt

• Soft cheese (unless mold is part of the product)

• Jam

• Leftovers

• Cooked vegetables

• Soft fruits

The moisture in these foods allows mold to spread easily.

4. Some Hard Foods Can Be Saved

Certain hard foods may be salvageable if mold is removed properly.

Examples include:

• Hard cheese

• Hard salami

• Firm carrots

Cut away at least 1 inch (2.5 cm) around and below the moldy area, taking care not to let the knife touch the mold.

However, if you are unsure, it is safest to discard the food.

5. Mold Can Cause Allergic Reactions

Some people are sensitive to mold spores.

Exposure may cause:

• Sneezing

• Runny nose

• Coughing

• Wheezing

• Skin irritation

• Eye irritation

People with asthma or mold allergies may experience more severe symptoms.

6. Eating Moldy Food May Cause Food Poisoning

Accidentally eating moldy food can sometimes lead to:

• Nausea

• Vomiting

• Stomach cramps

• Diarrhea

Most healthy adults recover without complications, but symptoms can be more serious in vulnerable individuals.

7. People with Weakened Immune Systems Are at Higher Risk

Extra caution is needed for:

• Older adults.

• Infants and young children.

• Pregnant women.

• People receiving chemotherapy.

• Organ transplant recipients.

• Individuals with weakened immune systems.

These groups are more susceptible to infections and complications from contaminated food.

8. Proper Food Storage Helps Prevent Mold

Reduce the risk of mold by:

• Refrigerating perishable foods promptly.

• Keeping foods dry when appropriate.

• Storing grains and nuts in airtight containers.

• Checking expiration dates.

• Cleaning refrigerators regularly.

Proper storage slows mold growth and helps preserve food quality.

9. Some Foods Naturally Contain Beneficial Mold

Not all molds are harmful.

Certain cheeses are intentionally produced using carefully controlled molds, including:

• Blue cheese

• Brie

• Camembert

These molds are safe to eat because they are specifically selected and monitored during production.

10. Never Smell Moldy Food to Check if It's Safe

Smelling moldy food closely can expose you to mold spores that may irritate the nose and lungs.

If food appears moldy or has an unusual odor, it is safer to discard it rather than smell or taste it.

Foods Most Commonly Affected by Mold

Mold commonly grows on:

• Bread

• Fresh fruit

• Berries

• Tomatoes

• Cooked leftovers

• Nuts

• Grains

• Rice

• Coffee beans

• Spices

Regularly inspect these foods, especially if they have been stored for long periods.

How to Reduce Your Risk

To help prevent mold exposure:

• Buy only the amount of fresh food you can use.

• Refrigerate leftovers within two hours.

• Keep refrigerators below 40°F (4°C).

• Freeze foods you won't eat soon.

• Throw away foods that show extensive mold growth.

• Avoid consuming moldy nuts, grains, or peanut products.

The Bottom Line

While some molds are intentionally used to produce foods such as certain cheeses, unwanted mold on everyday foods can produce harmful mycotoxins and may cause food poisoning or allergic reactions. Soft foods with mold should usually be discarded, while some hard foods may be salvaged by cutting away a generous margin around the mold.

The safest approach is to store food properly, inspect it regularly, and avoid eating foods that show signs of spoilage or mold growth.