Raw milk is dangerous because it can carry bacteria that cause serious illness, and no amount of cleanliness on a farm can guarantee the milk is pathogen-free. Unpasteurized dairy products cause roughly 840 times more illnesses and 45 times more hospitalizations than pasteurized ones, according to CDC data from 2009 to 2014. The risk isn’t theoretical or rare. It’s a predictable consequence of skipping the heating step that kills harmful microorganisms in milk.
What’s Actually in Raw Milk
Milk leaves a cow’s udder warm and rich in nutrients, which makes it an ideal environment for bacterial growth. The pathogens most commonly found in raw milk include Campylobacter, Salmonella, Shiga toxin-producing E. coli (like E. coli O157:H7), and Listeria. Less common but still documented organisms include Brucella, Yersinia, and Mycobacterium bovis, the bacterium that causes bovine tuberculosis.
These bacteria can enter milk through multiple routes. Fecal matter from the cow is the most common source, since even small, invisible traces can contaminate the udder or milking equipment. Udder infections introduce bacteria directly into the milk itself. Environmental contamination from dirt, insects, or improperly sanitized storage tanks adds another layer of risk. A cow can also carry and shed pathogens without showing any signs of illness, so a healthy-looking animal is no guarantee of safe milk.
Why Testing Doesn’t Solve the Problem
Some raw milk producers test their products for pathogens, and buyers often take comfort in that. But testing has fundamental limitations that make it unreliable as a safety measure. Contamination in raw milk is sporadic. A cow might shed bacteria one day and not the next, so a clean test result on Monday says nothing about Tuesday’s milk. Bacteria also aren’t evenly distributed in milk. They tend to cluster in the fat layer, which means a sample drawn from one part of a container may miss organisms present in another.
Even when pathogens are present, their numbers can be too low for a test to detect, yet still high enough to make someone sick. Several of the key pathogens in raw milk have very low infectious doses, meaning it takes only a small number of organisms to cause illness. On top of that, pathogen testing takes days to complete. Since raw milk has a short shelf life, much of it is already consumed before results come back. And no test screens for every possible pathogen. Unusual or emerging organisms can slip through entirely. Testing a few batches before approving a producer, as some programs do, captures only a snapshot of a fraction of the milk produced during those weeks.
Illnesses Caused by Raw Milk
Most people who get sick from raw milk experience gastroenteritis: diarrhea, stomach cramps, vomiting, and fever. These symptoms typically appear within one to seven days of exposure, depending on the pathogen. For many otherwise healthy adults, the illness resolves on its own within a week, though it can be intensely unpleasant.
The real danger lies in the complications. E. coli O157:H7 can trigger hemolytic uremic syndrome, or HUS, a condition where toxins destroy red blood cells and damage the kidneys. Warning signs include reduced urination, unusual paleness, unexplained bruising or tiny red spots on the skin, blood in the urine, and extreme fatigue. HUS can lead to kidney failure, permanent organ damage, and death. Most people recover within a few weeks, but some do not recover fully.
Campylobacter infection can lead to Guillain-Barré syndrome, a neurological condition where the immune system attacks the body’s own nerves, causing muscle weakness and sometimes temporary paralysis. Listeria poses a particular threat during pregnancy: infection can cause miscarriage, stillbirth, or life-threatening illness in a newborn. Salmonella, the other major culprit, is responsible for a large share of dairy-related hospitalizations each year. Across all pathogens, dairy-related outbreaks in the U.S. cause an average of 760 illnesses and 22 hospitalizations per year, with unpasteurized products driving the overwhelming majority.
Who Faces the Greatest Risk
Children under 5, adults over 65, pregnant women, and people with weakened immune systems are at significantly higher risk of severe illness from raw milk. Young children are especially vulnerable to HUS from E. coli, and their smaller bodies have less capacity to tolerate dehydration from prolonged diarrhea. Older adults face similar risks because aging immune systems mount a weaker defense against bacterial infections, and pre-existing kidney or liver conditions compound the danger.
Pregnant women are about 10 times more likely than the general population to develop listeriosis. The infection may cause only mild flu-like symptoms in the mother while devastating the pregnancy. People on immunosuppressive medications, undergoing chemotherapy, or living with HIV face prolonged and more severe infections from any of these pathogens. For these groups, a single glass of contaminated raw milk can result in hospitalization or worse.
The Bird Flu Factor
Since 2024, a new risk has entered the picture. The H5N1 avian influenza virus has been spreading among U.S. dairy cattle, and viral genetic material has been detected in a substantial share of retail milk samples. During a surveillance period in spring 2024, influenza A virus was found in over 36% of pasteurized retail milk samples, including from states with no reported outbreaks in dairy herds at the time. The reassuring finding: no viable virus was recovered from any pasteurized sample. Pasteurization destroyed the virus completely.
Raw milk offers no such protection. The U.S. Department of Agriculture responded to the outbreak by requiring mandatory testing of raw, unpasteurized milk and testing before interstate movement of dairy cattle. While the long-term human health risk from H5N1 in raw milk is still being monitored, the episode illustrates a broader point: new threats can appear in the milk supply at any time, and pasteurization is the only reliable defense against pathogens you don’t even know to look for yet.
What Pasteurization Actually Does to Milk
A common reason people seek out raw milk is the belief that pasteurization strips away important nutrients. The data doesn’t support this. Protein quality and digestibility are identical in raw and pasteurized milk. Studies measuring protein digestibility found no difference: roughly 80% in both cases. The major proteins in milk, caseins, are structurally unaffected by pasteurization temperatures. Whey proteins undergo only limited changes.
Vitamins fare similarly well. Riboflavin, B6, and B12, the vitamins milk provides in meaningful amounts, are heat-stable and survive pasteurization intact. The one vitamin that does take a hit is vitamin C, which drops by about 15 to 17% during standard pasteurization. But milk is not a significant source of vitamin C to begin with. A glass of raw milk contains roughly 24 milligrams per liter, while a single orange provides about 70 milligrams. The vitamin C lost during pasteurization is nutritionally insignificant.
Claims that raw milk contains beneficial enzymes that aid digestion also don’t hold up. The enzymes present in cow’s milk are bovine enzymes, not human digestive enzymes. They serve no established function in human digestion, and stomach acid breaks down most proteins and enzymes regardless of whether the milk was heated first.
Why It’s Federally Banned for Sale Across State Lines
Federal law prohibits the sale of raw milk in final package form for direct human consumption across state lines. The regulation, found in Title 21 of the Code of Federal Regulations, requires that all milk and milk products shipped in interstate commerce be pasteurized. The standard process heats every particle of milk to at least 161°F (72°C) for 15 seconds, or 145°F (63°C) for 30 minutes for the slower batch method.
State laws vary widely. Some states allow raw milk sales at retail stores, others permit only farm-direct sales, and a handful ban all raw milk sales entirely. But the federal interstate ban reflects a consistent scientific consensus: unpasteurized milk carries inherent risk that can’t be managed through farm hygiene or testing alone. The contamination is too sporadic, the infectious doses are too low, and the consequences for vulnerable people are too severe.