Four groups face the highest risk of severe food poisoning: adults 65 and older, children under 5, pregnant women, and people with weakened immune systems. Anyone can get a foodborne illness, but for these groups, the same infection that causes a rough couple of days for a healthy adult can lead to hospitalization or worse. Beyond these well-known categories, certain medications and chronic conditions also raise risk in ways many people don’t realize.
Adults Over 65
Aging changes the body’s defenses at nearly every level. The gut slows down, moving food through the digestive tract more slowly and giving bacteria more time to multiply. The lining of the intestines becomes less effective at blocking pathogens from entering the bloodstream. And the immune system itself shifts: the cells responsible for attacking new infections decline, while the body’s chemical signaling molecules that coordinate immune responses become less efficient.
These changes stack up. Although children under 5 actually get food poisoning more often in raw numbers, adults over 50 are hospitalized and die from foodborne illness at significantly higher rates than any other age group. The liver and kidneys, which normally filter out bacteria and toxins, also lose some of their capacity with age, making it harder to recover once an infection takes hold.
Children Under 5
Young children get food poisoning more frequently than adults, and their bodies handle it worse. Their immune systems are still developing, which means they can’t fight off harmful bacteria as effectively. They also produce less stomach acid, one of the body’s first lines of defense against swallowed pathogens.
The more immediate danger for infants and toddlers is dehydration. Vomiting and diarrhea drain fluids fast in a small body. Warning signs include little or no urination, extreme thirst, weakness, dizziness, or changes in alertness or behavior. Any fever in a child under 2 warrants a call to a healthcare provider, as does a fever above 102°F in older children.
Pregnant Women
Pregnancy naturally shifts the immune system to protect the developing baby, but that shift also makes the body less equipped to fight certain infections. Listeria is the most concerning. About 1 in 25,000 pregnant women in the U.S. contract a Listeria infection each year, and the consequences are severe: 1 in 4 who get sick lose their pregnancy or their baby shortly after birth. Listeria can cross the placenta and harm the baby even when the mother feels only mildly ill, which makes it easy to dismiss early symptoms as normal pregnancy fatigue.
This is why the food avoidance list for pregnant women is so specific. Soft cheeses made from unpasteurized milk (like queso fresco, brie, and camembert), deli meats that haven’t been reheated, refrigerated smoked seafood, and unpasteurized juice or cider all carry higher Listeria risk. Early treatment can save the baby, so persistent flu-like symptoms during pregnancy deserve prompt attention.
People With Weakened Immune Systems
This is the broadest category, and it includes more people than you might expect. Anyone undergoing cancer treatment, taking medications that suppress the immune system (for organ transplants or autoimmune conditions), or living with HIV/AIDS falls into this group. People with HIV/AIDS are especially vulnerable to Listeria, Salmonella, Campylobacter, and parasitic infections, and their illnesses tend to last longer and require more hospitalization.
Diabetes, Kidney Disease, and Liver Disease
Chronic conditions that don’t seem directly related to digestion can still raise food poisoning risk substantially. Diabetes is a prime example. High blood sugar suppresses the white blood cells that fight infection. Diabetes can also reduce stomach acid production and slow the movement of food through the digestive tract, giving bacteria more time and a more hospitable environment to multiply. On top of that, kidney damage from diabetes means the body is less able to filter out harmful bacteria once they’re circulating.
Liver disease works similarly. The liver is one of the body’s primary detoxification organs, and when it’s compromised, bacteria and toxins that would normally be cleared can build to dangerous levels. People with cirrhosis are particularly vulnerable to a type of bacteria found in raw shellfish that can cause life-threatening bloodstream infections.
Medications That Lower Your Defenses
Stomach acid is a powerful barrier against foodborne pathogens, and millions of people take medications that reduce it. Proton pump inhibitors, commonly prescribed for acid reflux and ulcers, suppress acid production so effectively that they can make the stomach a far more hospitable place for swallowed bacteria. One large population study found that people taking these medications had roughly 5.5 times the odds of developing a gut infection compared to people not taking them. The effect is tied to how much acid suppression the drug causes: stronger acid blockers carry a higher risk than milder ones.
These medications also disrupt the balance of bacteria in the gut, weaken certain immune cells, and alter the pH of the small intestine in ways that allow dangerous bacteria like Salmonella, Campylobacter, and C. difficile to colonize areas they normally couldn’t survive. If you take acid-reducing medication regularly, you’re in a higher risk category for food poisoning even if you’re otherwise healthy.
Foods That Carry the Most Risk
For anyone in a high-risk group, certain foods are worth avoiding entirely rather than relying on careful handling. The CDC’s riskier-choice list includes:
- Raw or undercooked meat and poultry, including rare burgers and pink chicken
- Deli meats and hot dogs that haven’t been reheated until steaming
- Raw or undercooked eggs, including foods made with them like Caesar dressing, raw cookie dough, and homemade eggnog
- Raw or undercooked seafood, including sushi, sashimi, ceviche, and refrigerated smoked fish like lox
- Soft cheeses made from unpasteurized milk, and any fresh soft cheese like queso fresco regardless of pasteurization
- Unpasteurized milk and juice
- Raw sprouts of any kind (alfalfa, bean, clover)
- Premade deli salads like coleslaw, potato salad, tuna salad, and chicken salad
- Raw flour and any batter or dough made with it
- Cut melon left at room temperature for more than two hours (one hour above 90°F)
When cooking at home, a food thermometer is the only reliable way to know food has reached a safe temperature. Poultry needs to hit 165°F throughout. Ground beef and pork need 160°F. Beef steaks and roasts are safe at 145°F. Color alone is not a reliable indicator for any of these.
Warning Signs That Need Attention
Most food poisoning resolves on its own, but for people in high-risk groups, certain symptoms signal something more serious. Blood or pus in the stool, severe abdominal pain, vomiting that won’t stop, and diarrhea lasting more than a day all warrant medical care. Nervous system symptoms like blurred or double vision, tingling skin, muscle weakness, or confusion can indicate a more dangerous type of foodborne illness, such as botulism, and need emergency attention.
In young children, watch for signs of dehydration: no wet diapers, no tears when crying, sunken eyes, or unusual drowsiness. In older adults, dehydration can set in quickly and may show up as confusion or dizziness before the person recognizes they’re in trouble.