Eating spoiled feta cheese typically causes a bout of food poisoning with nausea, vomiting, stomach cramps, and diarrhea that resolves within one to three days. In most cases, the illness is unpleasant but not dangerous. The exception is contamination with certain bacteria, particularly Listeria, which can cause serious illness in pregnant women, older adults, and anyone with a weakened immune system.
How to Tell Feta Has Gone Bad
Fresh feta smells tangy and mildly sour. When it spoils, the color darkens, the texture turns mushy and oozing (or dries out completely and hardens), and the cheese develops a strong, stinky odor that’s clearly different from its normal sharpness. Any visible mold is the clearest signal to throw it out.
Unlike hard cheeses such as cheddar or Parmesan, you cannot safely cut mold off feta and eat the rest. Feta is a soft, crumbly cheese with high moisture content, which means mold threads can spread invisibly throughout the block. Harmful bacteria like Listeria, Salmonella, and E. coli can grow alongside the mold even in areas that look perfectly fine. If you see any mold at all, the entire container should go in the trash.
What You’ll Likely Feel
Most people who eat a small amount of spoiled feta experience standard food poisoning symptoms: nausea, vomiting, watery diarrhea, and abdominal cramps. These usually start within 6 to 24 hours and clear up on their own within a day or two. Staying hydrated is the most important thing you can do during this window. Water, broth, and electrolyte drinks help replace what your body loses.
If you ate a large amount or the cheese was heavily contaminated, symptoms can be more intense and last longer. Fever, persistent vomiting that prevents you from keeping fluids down, bloody diarrhea, or symptoms lasting more than three days are signs of a more serious infection that needs medical attention.
The Bacteria That Make Spoiled Feta Dangerous
The main pathogens associated with contaminated cheese are Listeria monocytogenes, Staphylococcus aureus, Salmonella, and various strains of E. coli. Of these, Listeria and Staph aureus are the most frequently found in cheese products based on prevalence surveys. Salmonella and E. coli tend to cause the classic rapid-onset food poisoning most people picture: stomach distress that hits within hours and fades relatively quickly.
Listeria is different and more concerning. It can survive and even multiply at refrigerator temperatures, which means feta stored in the fridge isn’t necessarily safe just because it’s been kept cold. An invasive Listeria infection, called listeriosis, produces fever, muscle aches, fatigue, headache, stiff neck, confusion, loss of balance, and in severe cases, seizures. The incubation period is unusually long: symptoms can take up to two weeks to appear after eating the contaminated food, which makes it harder to trace back to a specific meal.
Risks for Pregnant Women
Pregnant women face a dramatically higher risk from Listeria. Hormonal changes during pregnancy suppress the immune system to protect the fetus, but this also makes the body roughly 14 times more likely to develop listeriosis compared to non-pregnant adults. The fetus is especially vulnerable to Listeria infection, which can lead to miscarriage, stillbirth, premature delivery, or a life-threatening infection in the newborn.
This is why pregnant women are specifically advised to avoid soft cheeses made with unpasteurized (raw) milk, including feta, Brie, Camembert, blue-veined cheeses, and queso fresco. Feta made from pasteurized milk and stored properly carries much less risk, but once it shows any signs of spoilage, the same rules apply to everyone: discard it entirely.
Who Else Should Be Cautious
Beyond pregnant women, people over 65, anyone undergoing chemotherapy, organ transplant recipients, and those with conditions like HIV/AIDS or diabetes that affect immune function are all more susceptible to severe foodborne illness. For these groups, what might be a mild stomachache in a healthy adult can escalate to a systemic infection requiring hospitalization. If you fall into any of these categories and recently ate feta you suspect was spoiled, monitoring for fever and unusual fatigue over the following two weeks is worthwhile given Listeria’s long incubation period.
How to Store Feta Safely
Feta lasts longest when kept submerged in its brine (the salty liquid it’s packaged in). Once opened, feta stored in brine in a sealed container stays good for about four to six weeks in the refrigerator. Without brine, it dries out and spoils much faster, typically within a week. If your feta came in a vacuum-sealed block without brine, you can make a simple brine at home by dissolving a teaspoon of salt in a cup of water and pouring it over the cheese in an airtight container.
Feta left out at room temperature for more than two hours enters the danger zone where bacteria multiply rapidly. If you accidentally left it on the counter overnight, it’s not worth the risk, even if it looks and smells normal. Bacteria that cause illness don’t always produce visible spoilage.