The odds of any single egg being contaminated with Salmonella are roughly 1 in 20,000. That means if you cracked a raw egg into a smoothie every morning, you’d statistically encounter a contaminated egg about once every 55 years. The risk per egg is low, but it’s not zero, and several factors can push that number higher or lower depending on how eggs are stored, handled, and prepared.
How Often Eggs Actually Carry Salmonella
The most widely cited estimate comes from a study published in the International Journal of Food Microbiology, which calculated that approximately 1 in every 20,000 eggs produced annually in the United States is internally contaminated with Salmonella Enteritidis. The 90% certainty range spans from 1 in 30,000 (best case) to 1 in 12,000 (worst case). Those figures represent eggs at the time of production, before any additional handling, storage mistakes, or time-related bacterial growth.
To put that in everyday terms: a standard carton of 12 eggs has about a 0.06% chance of containing one contaminated egg. If you eat two raw eggs a week, your annual probability of encountering a contaminated one is somewhere around 0.5%. Most people who eat the occasional raw egg in cookie dough or a homemade dressing will never run into a problem. But across an entire population consuming billions of eggs a year, those small odds still add up to real illnesses. A 2025 outbreak linked to shell eggs, for instance, sickened 105 people across 14 states, with 19 hospitalizations.
How Salmonella Gets Inside an Egg
There are two routes, and the more dangerous one happens before the egg is even laid. In what’s called transovarian transmission, a hen carrying Salmonella Enteritidis in her intestinal tract can spread the bacteria to her reproductive organs. Immune cells called macrophages, which are supposed to fight off the infection, actually get hijacked by the bacteria and carry them deeper into the body. Once the reproductive tract is colonized, the bacteria can contaminate the egg white or yolk membranes while the egg is still forming inside the hen, before the shell ever seals shut. No amount of washing the outside of that egg will help.
The second route is external. Other strains of Salmonella can land on the eggshell from contact with droppings or a colonized reproductive tract during laying. As a freshly laid egg cools, it contracts slightly, creating a small pressure difference that can pull bacteria on the surface through the shell’s microscopic pores. This is one reason commercial eggs in the U.S. are washed and refrigerated, though it also means the shell’s natural protective coating is removed, making refrigeration even more important.
Why Storage Temperature Matters So Much
A contaminated egg straight from the hen may contain only a tiny number of Salmonella cells, often too few to make a healthy adult sick. The real danger is what happens next. Research on experimentally contaminated eggs found that bacterial counts barely budged in eggs stored at 4°C (about 39°F, standard refrigerator temperature). But eggs held at room temperature (21°C/70°F) or warmer for more than 20 days saw bacterial populations explode by a millionfold or more.
This is why refrigeration is the single most important thing you can do to limit your risk. A contaminated egg kept cold the entire time from farm to your kitchen may never reach a dangerous bacterial load. The same egg left on a countertop for a few weeks becomes a genuinely risky food. If you buy eggs from a farmer’s market or backyard flock where refrigeration practices vary, getting them into your fridge quickly matters even more.
Who Faces the Greatest Risk
For a healthy adult, a bout of Salmonella typically means 12 to 72 hours of diarrhea, fever, and abdominal cramps that resolves on its own within a week. Unpleasant, but rarely dangerous. The picture changes for certain groups. Young children (especially under 5), adults over 65, pregnant women, and anyone with a weakened immune system are more likely to develop severe or invasive infections where the bacteria spread beyond the gut into the bloodstream. For these groups, the same low-probability event carries disproportionately high consequences, which is why most food safety guidelines specifically warn them against consuming raw or undercooked eggs.
How to Eliminate the Risk
Cooking eggs to the point where both the white and yolk are firm kills Salmonella reliably. Scrambled eggs, hard-boiled eggs, and well-cooked omelets pose essentially no risk. The gray area is preparations where eggs stay runny or completely raw: sunny-side up, soft-poached, homemade mayonnaise, Caesar dressing, mousse, or raw cookie dough.
If you regularly make recipes that call for raw or undercooked eggs, pasteurized shell eggs are the simplest solution. These eggs have been heat-treated at temperatures high enough to destroy Salmonella without cooking the egg itself. They look and taste like regular eggs, and the FDA considers them safe for raw use. The packaging will typically note that the eggs have been pasteurized. Liquid pasteurized egg products (sold in cartons) work the same way for recipes where whole-shell presentation doesn’t matter.
For standard unpasteurized eggs, keeping them refrigerated at all times, using them before the expiration date, and cooking them thoroughly covers the vast majority of risk. Avoiding cracked or visibly dirty eggs also helps, since shell damage gives bacteria an easy entry point.
Putting the Risk in Perspective
Eating a single raw egg is, statistically, very safe. The contamination rate is low, and even a contaminated egg kept properly refrigerated may not contain enough bacteria to cause illness. The risk compounds with frequency, poor storage, and vulnerability. Someone who makes fresh raw egg protein shakes daily from unrefrigerated, unpasteurized eggs is playing much worse odds than someone who licks cake batter off a spoon once a month. For most people, the occasional encounter with a raw or runny egg is a small gamble with overwhelmingly favorable odds. For those who’d rather not gamble at all, pasteurized eggs remove the bet entirely.