Yes, you can get food poisoning from nuts. Salmonella is the most common culprit, and it has caused multiple large-scale outbreaks linked to peanuts, almonds, pistachios, and other varieties. Nuts can also harbor mold-produced toxins and, when stale or rancid, contain oxidation byproducts that cause digestive symptoms.
Why Bacteria Thrive in Nuts
Nuts are dry foods with very low moisture, and that dryness actually works in Salmonella’s favor once the bacteria are present. In moist foods, heat kills Salmonella relatively quickly. But in low-moisture environments like peanut butter (which has a water activity of 0.35 or less), the bacteria become far more heat resistant. The FDA notes that in a moist food, it takes less than 5 minutes at 140°F to destroy Salmonella. In a drier food, the same temperature needs 50 minutes, and in something as dry as peanut butter, it takes even longer.
This means Salmonella can survive in nuts and nut butters for months, even at room temperature. It doesn’t need to grow to make you sick. A small number of cells can cause illness because the fatty, low-acid environment of nuts helps bacteria survive stomach acid and reach the intestines.
How Nuts Get Contaminated
Contamination typically happens before nuts ever reach a processing facility. Many tree nuts, including almonds, pecans, and walnuts, are harvested by shaking them to the ground. Once on the orchard floor, they pick up whatever is in the soil. Wild animals like deer, hogs, squirrels, and turkeys commonly wander through orchards and deposit feces that carry Salmonella and E. coli. Research has found that pecan orchards where livestock grazed had six times higher E. coli contamination than ungrazed orchards.
Salmonella isolation rates in almond orchards spike during the harvest months of August through October, likely because the harvesting process kicks up contaminated dust that spreads bacteria across the orchard. Wet weather makes things worse: moisture helps soil and debris cling to nut surfaces, and rain or irrigation can help Salmonella survive and even multiply in orchard soil. Contaminated harvesting equipment spreads the problem further.
Some nuts, including macadamias, pecans, and walnuts, are soaked in water to soften their shells before cracking. If that water carries bacteria, it can contaminate entire batches. Chlorine treatments that work well in other food processing settings are less effective here because the high organic load in the water neutralizes the chlorine. Even chlorinated water at 400 parts per million failed to significantly reduce Salmonella on in-shell pecans after 24 hours of soaking.
Salmonella Symptoms and Timeline
If you eat nuts contaminated with Salmonella, symptoms typically appear anywhere from 6 hours to 6 days later. The most common signs are diarrhea (sometimes bloody), stomach cramps, fever, and vomiting. Most people recover within a few days without treatment, but young children, older adults, and anyone with a weakened immune system face a higher risk of severe illness.
The delayed onset is one reason nut-related food poisoning often goes unrecognized. By the time symptoms start, most people don’t connect them to the handful of cashews or the peanut butter sandwich they had days earlier.
Aflatoxins: A Hidden Mold Risk
Certain molds that grow on nuts produce aflatoxins, which are among the most potent naturally occurring toxins. Peanuts, Brazil nuts, and pistachios are the most susceptible. The mold responsible grows in warm, humid conditions, both in the field and during storage.
Eating a large amount of aflatoxin at once, or smaller amounts over several days, can cause liver failure and potentially death. Long-term exposure at lower levels raises the risk of liver cancer and can damage the kidneys and immune system. The FDA sets a legal limit of 20 parts per billion for total aflatoxins in peanuts and peanut products. Nuts exceeding this threshold are considered adulterated and subject to seizure.
In practice, commercial nut processing in the U.S. includes sorting and testing that removes most contaminated product before it reaches store shelves. The greater risk comes from unregulated sources: homegrown peanuts, nuts bought from informal markets, or imported products from countries with less rigorous testing.
Rancid Nuts and Digestive Problems
Even without bacterial contamination, old or improperly stored nuts can make you sick. Nuts are high in unsaturated fats, which break down through a process called lipid oxidation. This produces a range of compounds, primarily aldehydes, that give rancid nuts their characteristic stale, paint-like smell. Research on walnut kernels identified specific breakdown products including hexanal and other volatile compounds generated as the fats in nuts degrade.
Eating rancid nuts can cause vomiting and diarrhea. The oxidation process also destroys the beneficial antioxidants in nuts, so rancid nuts lose their nutritional value at the same time they become potentially harmful. You’ll usually be able to tell: rancid nuts taste bitter or sour and smell distinctly off. If a nut doesn’t taste right, spit it out.
Raw Nuts vs. Roasted Nuts
Raw nuts carry a higher food poisoning risk than roasted ones. The heat from roasting is enough to kill Salmonella and most other bacteria on nut surfaces. Roasting also reduces aflatoxin levels. This is one reason the almond industry in the U.S. now requires all commercially sold almonds to undergo a pasteurization step, either through roasting, blanching, steaming, or another approved treatment.
That said, roasting doesn’t eliminate every risk. If peanut butter or a nut paste retains pockets of unprocessed product (visible as lumps or swirls), bacteria inside those pockets remain in a low-moisture environment where they’re extremely heat resistant. This is why recalls sometimes involve products that were technically heat-treated.
How to Store Nuts Safely
Proper storage prevents both rancidity and mold growth. The optimal temperature for nut storage is 32°F to 50°F (0°C to 10°C) with relative humidity between 55% and 70%. For most people, this means keeping nuts in the refrigerator or freezer rather than in a pantry. At room temperature, especially in warm or humid climates, fats oxidize faster and mold grows more readily.
Different nuts need slightly different moisture levels to stay fresh. Walnuts and pecans do best at about 5% moisture content, peanuts and pistachios at 7%, and cashews at 8%. You don’t need to measure this at home. The practical takeaway is to store nuts in airtight, moisture-proof containers in the fridge. Shelled nuts go rancid faster than unshelled ones because more surface area is exposed to air. Whole nuts in their shells, kept cool and dry, can last many months. Once opened, use nuts within a few weeks if kept at room temperature, or within several months if refrigerated.
If you buy nuts in bulk, smell and taste a few before eating a large amount. A bitter, sharp, or chemical taste is a clear sign of rancidity. Visible mold, discoloration, or a musty smell suggests fungal contamination. In either case, throw them out.