Blue cheese is safe to eat for most people. The mold that gives it those distinctive blue-green veins is a carefully selected, food-grade fungus that has been used in cheesemaking for centuries. That said, a few specific groups need to be cautious, and how you store and handle blue cheese matters for keeping it safe.
Why the Mold in Blue Cheese Won’t Hurt You
The mold used in blue cheese, called Penicillium roqueforti, is not the same as the fuzzy mold that grows on forgotten leftovers. Cheesemakers use specific strains selected for safety and flavor, and these strains have low toxin-producing potential. While Penicillium roqueforti can technically produce a compound called PR toxin, the chemistry inside a wheel of blue cheese works against it. The low-oxygen environment and the nitrogen-rich compounds naturally present in cheese (amino acids, casein) cause PR toxin to break down rapidly into much less harmful molecules. Studies looking for PR toxin in finished blue cheese have consistently found it either absent or at insignificant levels.
Other trace metabolites have been detected in blue cheese at very low parts-per-million levels, but none at concentrations considered a safety concern for consumers. In short, the mold in your blue cheese was put there on purpose, and the conditions inside the cheese keep it from producing anything dangerous.
Who Should Avoid Blue Cheese
Pregnant Women
Blue cheese lands on the CDC’s “riskier choice” list for pregnancy. Pregnant women are 10 times more likely than the general population to develop a Listeria infection, and soft, mold-ripened cheeses (including blue-veined varieties) can harbor this bacterium, especially when made from unpasteurized milk. If you’re pregnant and craving blue cheese, the safer option is to heat it to an internal temperature of 165°F or until it’s steaming hot, which kills Listeria. Hard cheeses made with pasteurized milk are a lower-risk alternative.
People Taking MAOIs
If you take a type of antidepressant known as an MAOI (monoamine oxidase inhibitor), blue cheese is one of the foods you’ve likely been told to avoid. The reason is tyramine, a compound that builds up in aged and fermented foods. Blue cheese contains highly variable tyramine levels, with studies finding anywhere from 10 to over 1,500 milligrams per kilogram depending on the sample. A sensitive person on an MAOI can experience a significant spike in blood pressure from as little as 10 to 20 milligrams of tyramine in a single sitting. A 28-gram (one-ounce) serving of a high-tyramine blue cheese could easily hit that threshold. This interaction can cause dangerously high blood pressure, so people on MAOIs should treat blue cheese as off-limits unless their prescriber says otherwise.
People Sensitive to Histamine
Aged cheeses, blue varieties included, contain histamine. For most people this isn’t a problem, but individuals with histamine intolerance can experience flushing, headaches, dizziness, sweating, and sometimes abdominal pain or diarrhea after eating them. Blue cheese left at room temperature builds up histamine faster. If you notice these symptoms consistently after eating aged cheeses, histamine intolerance is worth exploring with your doctor.
Pasteurized vs. Unpasteurized
One of the biggest safety variables is whether the cheese was made with pasteurized or unpasteurized (raw) milk. In the United States, the FDA requires that any cheese made from raw milk be aged for at least 60 days at a minimum temperature of 35°F. This aging period allows salt, acidity, and competition from beneficial bacteria to reduce harmful pathogens. Many domestic blue cheeses use pasteurized milk, which eliminates most dangerous bacteria before production even begins.
Imported blue cheeses, particularly traditional European varieties, are more likely to be made from raw milk. These are still legal to sell in the U.S. as long as they meet the 60-day aging rule, but they carry slightly more risk for vulnerable populations. If you’re immunocompromised or pregnant, checking the label for “pasteurized milk” is a simple way to reduce your risk.
Sodium: Higher Than You’d Think
Blue cheese packs roughly 370 milligrams of sodium per one-ounce (28-gram) serving, which is about 16% of the recommended daily value. That’s twice the sodium in the same amount of cheddar. If you’re watching your salt intake for blood pressure or heart health, this is worth factoring in, especially since blue cheese is easy to eat in larger quantities when crumbled over a salad or melted into a sauce.
A Possible Upside for Heart Health
Fermented cheeses like blue cheese contain a compound called spermidine, which has drawn interest from researchers studying cardiovascular aging. In animal studies, dietary spermidine extended lifespan and was associated with reduced thickening of the heart muscle, less inflammation, and better preservation of heart cell function. Data from a large human cohort study found that people with higher dietary spermidine intake had lower blood markers associated with heart failure. Blue cheese isn’t the only source (beans, mushrooms, and other fermented foods contain it too), but it’s one of the richer ones in a typical Western diet. This doesn’t mean blue cheese is a health food, but it does suggest that moderate consumption fits comfortably into a balanced diet.
How to Store Blue Cheese Safely
Once opened, blue cheese keeps for about three weeks in the refrigerator if you wrap it tightly. The key is minimizing air exposure, which accelerates both spoilage and the development of unwanted molds (the kind you didn’t sign up for). Parchment paper or wax paper followed by a layer of foil or plastic wrap works well. If you won’t finish it within three weeks, wrapping it tightly and freezing it extends its life, though the texture may become more crumbly after thawing.
If you notice pink, orange, or fuzzy grey-green mold that looks different from the original blue-green veins, or if the cheese develops an ammonia smell strong enough to make you pull back, it’s time to discard it. The intentional mold in blue cheese has a sharp, tangy smell, but it shouldn’t be overwhelming or chemical.