The odds are low but not zero. The USDA has estimated that roughly 1 in 20,000 commercial eggs in the United States is internally contaminated with Salmonella, which works out to 0.005%. Field studies of flocks already known to be positive for the bacteria found slightly higher rates, closer to 5 in 20,000 (0.025%). In practical terms, if you cracked a raw egg into a smoothie every morning, you’d statistically encounter a contaminated egg once every 55 years at the national average rate.
Why the Risk Is Low but Real
Salmonella can get inside an egg before the shell even forms. When a hen’s reproductive tract is infected, the bacteria can be deposited directly into the developing egg, settling in the yolk or the white. This means washing the shell does nothing to remove it. The contamination is internal, invisible, and undetectable without lab testing.
Even when an egg does carry Salmonella, the number of bacteria inside a freshly laid egg is typically very small. The yolk membrane acts as a barrier, keeping bacteria confined to the white where nutrients are limited and natural antimicrobial proteins slow their growth. The danger increases over time, especially if the egg is stored at warm temperatures. As the yolk membrane degrades, bacteria can cross into the nutrient-rich yolk and multiply rapidly.
How Temperature Changes the Odds
Refrigeration is the single biggest factor determining whether a contaminated egg stays low-risk or becomes dangerous. A simulation study modeling 50,000 eggs found that at room temperature, 89 eggs developed significant Salmonella growth by the time a consumer would use them. When stored at refrigerator temperatures (roughly 39 to 43°F), that number dropped to just 5 out of 50,000. Cold temperatures keep the yolk membrane intact longer and stall bacterial multiplication.
The FDA recommends storing eggs at 40°F or below immediately after purchase. If eggs sit on a counter for hours, especially in a warm kitchen, you’re compressing the timeline for bacterial growth. This matters most for eggs you plan to use raw or undercooked, since cooking would kill any bacteria that had multiplied.
Backyard Eggs vs. Store-Bought
If you keep chickens or buy from a local farm, the risk picture looks a bit different. A 2024 NC State study testing both backyard and commercial flocks found Salmonella in 19.1% of backyard farm samples compared to 52.3% of commercial farm samples. That might sound like backyard eggs are safer, but context matters. Commercial eggs go through washing, grading, and mandatory refrigeration under USDA inspection. Backyard eggs typically don’t.
The study also found that antibiotic-resistant Salmonella strains were present in both systems, though resistance to key antibiotics was far more common in commercial samples (33%) than backyard ones (1%). For the average consumer, the takeaway is that neither source is risk-free. Backyard flocks may carry less Salmonella overall, but without the standardized safety chain that commercial eggs pass through, individual batches can vary widely.
What Happens If You Do Get Sick
Symptoms typically start 6 hours to 6 days after eating a contaminated egg. The hallmarks are watery diarrhea (sometimes bloody), severe stomach cramps, nausea, vomiting, and headache. Most people recover within 4 to 7 days without treatment.
About 8% of people with a confirmed Salmonella infection develop invasive disease, where the bacteria spread beyond the gut into the bloodstream, bones, or joints. This is rare in healthy adults but significantly more likely in infants, adults over 50, and anyone with a weakened immune system. A less common but notable complication is reactive arthritis, which causes joint pain, eye irritation, and painful urination. It can persist for months or even years and is most frequent in people aged 15 to 35.
Who Should Avoid Raw Eggs Entirely
For a healthy adult, eating a runny egg or a spoonful of cookie dough is a gamble with very favorable odds. But certain groups face disproportionately severe consequences if they lose that gamble. Infants, older adults, pregnant women, and people with compromised immune systems or heart disease are all at elevated risk for the serious complications described above. For these groups, the small probability of contamination isn’t worth the potential outcome.
How to Reduce Your Risk
If you want to eat raw eggs in recipes like Caesar dressing, homemade mayonnaise, or protein shakes, pasteurized eggs are the simplest solution. These are whole eggs in the shell that have been heat-treated to kill bacteria without cooking the egg itself. USDA research has shown that pasteurization kills 99.999% of Salmonella inside the egg while leaving the taste and texture intact. Pasteurized eggs are sold in most grocery stores, usually marked clearly on the carton.
Beyond choosing pasteurized eggs, a few habits make a meaningful difference. Buy eggs only from a refrigerated case and check that shells are clean and uncracked. Store them in the main body of your refrigerator, not the door, where temperatures fluctuate more. Use eggs within their sell-by date, since a longer shelf life gives bacteria more time to multiply if contamination is present. And wash your hands, utensils, and surfaces with hot soapy water after handling raw eggs, because the outside of the shell can carry bacteria even when the inside is clean.
Cooking eggs to 160°F kills Salmonella reliably. For scrambled eggs, omelets, or fried eggs, that means cooking until no liquid egg remains. For dishes where eggs are mixed into a larger recipe, a food thermometer is the only sure way to confirm the temperature has been reached throughout.