Is Penicillin Found in Any Food Products?

November 24, 2025 •

3 min read

Over 10% of people in the United States believe they have a penicillin allergy, yet approximately 90% of these individuals are not truly allergic. The misconception that penicillin can be found in common food products, particularly cheeses and spoiled bread, is widespread, but scientifically unfounded. In reality, the purified antibiotic used in medicine is produced under carefully controlled laboratory conditions, not found naturally in food.

Quick Summary

The antibiotic penicillin is a specific, purified drug, not naturally present in consumable foods like blue cheese or moldy items. While some foods utilize specific Penicillium molds for production, these are distinct strains from the one that produces the medicinal antibiotic and are safe to eat, unless spoiled or an allergy exists.

Key Points

No Penicillin in Food: The antibiotic penicillin is a purified medication produced in laboratories, not found naturally in food products.
Blue Cheese Molds Are Different: The Penicillium strains used to ripen blue cheese (e.g., P. roqueforti) are distinct from the antibiotic-producing strain and are safe to eat.
Moldy Food is Dangerous: Eating moldy bread or fruit is unsafe because random molds, including some Penicillium species, can produce poisonous mycotoxins.
Controlled Industrial Production: Medicinal penicillin comes from genetically engineered strains of Penicillium chrysogenum grown in deep fermentation tanks under controlled conditions.
Allergy Considerations: Individuals with a penicillin allergy generally do not need to avoid blue cheese, but those with a mold allergy should be cautious.
Purification is Key: The key difference lies in purification; the medicinal antibiotic is a refined chemical, whereas food mold is a complex living organism.

Distinguishing between the Antibiotic and the Fungus

Many people are confused about the relationship between the antibiotic penicillin and certain foods. This confusion arises because the medicinal drug is derived from a fungus belonging to the Penicillium genus. However, the genus contains many different species, and the specific ones used in food production are not the same as the one that produces the therapeutic antibiotic. The antibiotic used in medicine is purified from engineered strains of Penicillium chrysogenum (formerly P. notatum) under strict laboratory controls.

The Misconception of Blue Cheese and Penicillin

One of the most common myths is that blue cheeses contain the medical antibiotic penicillin. The blue veins in cheese varieties like Roquefort, Gorgonzola, and Stilton are created by the mold Penicillium roqueforti. Similarly, Brie and Camembert use Penicillium camemberti to create their white rinds.

Safe for most: These specific mold cultures are non-toxic and have been proven safe for human consumption for centuries.
No medicinal effect: The strains used for cheesemaking do not produce the specific antibacterial compound that makes penicillin an effective medicine.
Allergy considerations: While cross-contamination is not an issue, individuals with a mold allergy should exercise caution. The American Academy of Allergy, Asthma, and Immunology notes that the strains in cheese do not produce penicillin.

Why Moldy Food Does Not Contain Penicillin

Another widespread, and dangerous, belief is that eating moldy bread or fruit will provide a dose of penicillin. This is entirely false and poses significant health risks.

Toxic mycotoxins: Most molds that grow on food products, including many Penicillium species, produce harmful substances called mycotoxins. These toxins can cause serious illness if ingested.
Hidden growth: The mold visible on the surface is only a small part of the fungal colony. The roots, where mycotoxins are concentrated, can penetrate deep into the food.
Contamination risk: Random moldy food contains a mix of potentially dangerous fungi and bacteria, not a sterile, purified antibiotic.

The Commercial Production of Medicinal Penicillin

The production of medicinal penicillin is a complex, multi-stage industrial process far removed from a household pantry. It involves specialized equipment and highly controlled environments to ensure safety and potency.

Fermentation: High-yielding strains of Penicillium chrysogenum are grown in huge deep fermentation tanks.
Purification: The penicillin is then separated from the fungal culture and other byproducts.
Refinement: This crude extract is subjected to a rigorous purification process to isolate the specific antibiotic compound and remove any toxic impurities.
Sterilization and formulation: The final product is sterilized and formulated into pills or intravenous solutions for safe administration.

The Cantaloupe Story

A key moment in penicillin's history involved a moldy cantaloupe. During WWII, American researchers were desperately seeking a strain of Penicillium that produced higher yields of the antibiotic than the one discovered by Alexander Fleming. A laboratory assistant, Mary Hunt, found a moldy cantaloupe at a market in Peoria, Illinois. The fungus from this melon, Penicillium rubens NRRL 1951, proved to be much more productive, leading to the mass production that saved countless lives.

Comparison of Penicillium in Food vs. Medicine


Characteristic	Penicillium in Food Production	Medicinal Penicillin
Associated Species	P. roqueforti, P. camemberti, P. nalgiovense	P. chrysogenum (formerly P. notatum), P. rubens
Function	Develops flavor, texture, and appearance of cheese and cured meats	Treats bacterial infections by inhibiting cell wall synthesis
Safety	Considered safe for consumption (in processed products). Not meant for general ingestion from moldy surfaces.	Administered under medical supervision; must be prescribed.
Form	Live fungal culture, integral to the food product	Purified, concentrated, and formulated antibiotic drug
Effect on bacteria	Inactive against most pathogens, not a therapeutic agent	Highly effective against susceptible bacteria; resistance is a concern

Conclusion: A Clear Distinction

The notion that penicillin is found in any food is a myth. While specific, safe species of Penicillium mold are intentionally and carefully used to create delicacies like blue cheese, they are fundamentally different from the medicinal antibiotic. Attempting to ingest penicillin from moldy food is not only ineffective but also extremely dangerous due to the risk of ingesting toxic mycotoxins. The purified, therapeutic drug is a product of sophisticated industrial fermentation and refinement, available only via medical prescription. Understanding this crucial difference is vital for food safety and public health, especially for those with mold or penicillin allergies.

Frequently Asked Questions

No, you cannot get the antibiotic penicillin from eating moldy bread. The molds found on spoiled food are not the correct species, and they can produce dangerous mycotoxins that cause illness.

Yes, for most people. The Penicillium cultures used to make blue cheese, like P. roqueforti, do not produce the medicinal antibiotic. The American Academy of Allergy, Asthma, and Immunology confirms that it is generally safe for people with penicillin allergies to eat blue cheese.

Many molds, including species of Penicillium, produce mycotoxins that are harmful to human health. Additionally, mold often has deep roots that are invisible and can carry these toxins throughout the food.

Medicinal penicillin is produced in a laboratory setting using specific, high-yield strains of the Penicillium chrysogenum fungus. The antibiotic is isolated, purified, and formulated into a drug, not harvested from food.

No, the Penicillium genus includes many different species. Some are used safely in food production (like cheese), while others, including the one that produces the medicinal antibiotic, are different or can produce harmful toxins.

Food-grade molds are specific, non-toxic strains cultivated for their effect on flavor and texture in foods like cheese and cured meats. Medicinal molds are engineered strains used in a sterile lab setting to produce and purify the specific antibiotic compound.

No, this is a dangerous practice that can cause serious illness. The amount of penicillin, if any, is negligible, and the risk of ingesting harmful mycotoxins and other bacteria is high.