What happens if cats eat old wet food?

Quick answers

Cats eating old, spoiled wet food can potentially get sick from bacteria growth. However, a healthy cat’s digestive system is fairly resistant to small amounts of spoiled food. Cats tend to rely on their sense of smell to detect spoiled food and avoid eating it. Storing unopened wet food properly and following expiration dates can help prevent cats from eating spoiled wet food. Monitor cats after eating questionable food for vomiting, diarrhea or other signs of illness. Contact a vet if significant symptoms appear.

Wet or canned cat food provides important moisture and protein for cats’ diets. However, once opened and exposed to air, wet food can spoil more quickly than dry kibble. Cats are carnivores with short digestive tracts, making them vulnerable to foodborne illnesses from consuming spoiled foods. So what happens if cats eat old, spoiled wet cat food? This article examines the potential risks, a cat’s natural defenses, proper wet food storage and handling, signs of sickness, and when to see a vet.

How long can wet cat food sit out?

Once opened, wet or canned cat food should not sit out at room temperature for more than 2 hours tops according to experts. Bacteria can grow rapidly in the moist, protein-rich environment. Refrigerating opened cans can extend this to 3-5 days. But best practice is to discard any wet food that has been exposed to air and left out overnight. The expiration date on unopened cans, if stored properly, is around 2-3 years. However, spoiled food can make cats sick even before the expiration date if stored incorrectly. Monitor food for any odors, textures, or mold indicating it is spoiled.

Risks of eating old wet cat food

Wet cat food can grow harmful bacteria extremely quickly after opening. The most common risks of cats eating spoiled wet food include:


One of the most common types of food poisoning. Salmonella bacteria can survive and spread in wet cat food. Symptoms usually appear 12-72 hours after ingestion and include vomiting, diarrhea, fever, and abdominal pain. Salmonella can be life-threatening especially for very young or old cats.

E. coli

Another common bacteria that thrives on old wet food. Ingesting E. coli typically produces vomiting and bloody diarrhea within 2-8 days. It can cause severe illness or even death from dehydration without treatment.


Listeria monocytogenes bacteria is very hardy and can grow even in the fridge. Listeria causes vomiting, diarrhea, lethargy, loss of appetite, and fever typically within 24 hours of ingestion. It poses a high risk for pregnant cats as it can lead to miscarriage or stillbirth.


Staphylococcus aureus is a common skin bacteria that produces a toxin that can survive in wet cat food. Usually causes vomiting and diarrhea within a few hours of ingestion. Can be fatal if the toxin spreads to the intestines.


Mold spores spreading in old wet food can release toxins called mycotoxins. Ingesting too many mycotoxins can cause vomiting, diarrhea, liver damage, and negative neurological effects in cats.

Are cats able to detect spoiled food?

Fortunately, cats rely heavily on their excellent sense of smell to determine if food is safe. Studies show cats use olfaction for food selection more than taste. They have nearly 200 million scent receptors compared to only about 20-30 taste buds. If food smells “off” to a cat, they are likely to avoid eating it altogether. A cat’s natural food aversion behaviors help protect them from consuming dangerously spoiled foods.

However, kittens and very hungry cats may ignore odors and eat spoiled food anyway. Cats with an impaired sense of smell from a respiratory infection or nasal injury are also at higher risk. Relying on a cat’s nose alone to detect spoiled food is not foolproof. Pet owners still need to monitor food freshness and watch for signs of illness.

Proper wet cat food handling

To help prevent bacterial growth in open cans, it’s important to handle wet cat food properly:

Refrigerate after opening

Keep opened wet food refrigerated and covered. Refrigeration helps slow bacteria growth. Discard any leftover food after a few days.

Avoid contaminating food

When scooping food out of a can, be careful that utensils or surfaces don’t introduce new bacteria. Never add fresh food to already used food.

Don’t mix with dry food

Dry kibble can quickly become soggy and spoiled when mixed with wet food. Only combine what your cat will eat in one sitting.

Clean food bowls

Wash food bowls thoroughly after each use with soap and hot water. Bacteria left behind can contaminate the next meal.

Follow expiration dates

Check expiration or “best by” dates on cans before feeding. Do not feed cans that are long expired even if they look or smell okay.

Check for damage

Inspect cans for major dents, rust, bulging lids, or cracks that could compromise the seal and lead to spoilage.

Keep dry and cool

Store unopened cans in a cool, dry pantry away from direct sunlight and heat sources like appliances.

Following basic food safety guidelines can greatly reduce the risks of cats eating spoiled wet food and getting sick. But pet owners should still be vigilant.

Recognizing when wet cat food has spoiled

Clear signs wet cat food has spoiled include:

Unpleasant odor

Food that smells bad or “off” has likely started growing bacteria. However, small amounts of bacteria on the food surface can produce a spoiled smell before the inner contents are contaminated. Any unpleasant odors mean the food should be discarded.

Change in texture

Fresh wet food should have a smooth, pâté-like consistency. Spoiled food may appear slimy or excessively soft. Signs of slime, stickiness, or fuzzy mold indicate it is unsafe to eat.


Color changes like gray, green, or black discoloration signal decomposition. Some dark spots are okay-caused by natural ingredients. But extensive color change means spoilage.

Gas buildup inside can

Bulging or swollen cans with domed, convex lids indicate gas production from bacteria. Never taste food from an abnormally bulging can.

Relying on sight, smell and touch are the easiest ways to identify spoiled wet cat food. When in doubt, remember the old adage- if it looks bad or smells bad, don’t feed it!

Potential sickness from eating spoiled food

While cats have hardy digestive systems, consuming contaminated wet food still poses health risks. Here are common signs of sickness from eating spoiled food:


Frequent vomiting is the most obvious symptom. This is the body trying to eject harmful bacteria or toxins in the stomach before they are absorbed. Vomiting may happen immediately if food tasted rancid or be delayed a few hours as pathogens take effect.


Loose stools or outright diarrhea from irritation and inflammation of the intestines. May be watery and contain blood or mucus. Can lead to dehydration without treatment.

Loss of appetite

Refusal to eat or drink. Turning away from food and sniffing it without taking a bite. Loss of appetite indicates the cat feels unwell.


Being abnormally tired, depressed and inactive shows the body is mounting an immune response to infection rather than its usual alert, playful self.


Fever, excessive vomiting/diarrhea causes water loss and dehydration. Signs include dry gums, sunken eyes, poor skin elasticity. Dehydration makes cats prone to kidney failure.

Catching signs of illness early and contacting a vet promptly can prevent serious complications. Kittens, seniors and cats with compromised immune systems are most vulnerable to severe illness. But even healthy adult cats can get very sick from major amounts of contaminated food.

Should I induce vomiting?

If a cat eats a small bite of spoiled food but shows no symptoms, inducing vomiting is not necessary. Their stomach acid kills many bacteria, and their quick metabolism clears minor contamination. Inducing vomiting is recommended only if:

– Cat ate a significant amount of spoiled food within the past 2 hours.

– Cat appears ill or is showing signs of food poisoning.

– Certain dangerous toxins may be present like xylitol or lilies.

To induce vomiting, call your vet first. At home, give 2-4 tsp of 3% hydrogen peroxide by syringe or dropper into the cat’s mouth. This is only safe for cats over 6 months old. Kittens should see a vet to induce vomiting safely.

Only induce vomiting once. If repeated doses are needed, bring your cat to the vet for further treatment. Never induce vomiting if cat is lethargic or if vomiting has already begun.

Emergency vet care

Seek emergency vet care if cat shows any of these symptoms after eating spoiled food:

– Prolonged vomiting > 6 hours
– Signs of blood in vomit or stool
– Little/no urine production from dehydration
– Extreme lethargy, unable to stand
– Seizures

Emergency vet care provides IV fluids, electrolyte balancing, anti-nausea medication, and antibiotics if needed. The sooner sick cats get professional treatment, the better their prognosis. Bacterial sepsis can be fatal without aggressive rehydration and supportive care.

Preventing repeat incidents

After a cat gets sick from eating contaminated wet food, pet owners understandably want to prevent it from happening again. Here are some tips:

Limit free feeding

Free feeding allows cats to nibble wet food sitting out for hours. Instead, provide measured meals cats finish within an hour and promptly store or discard leftover food.

Separate cats when feeding

Competitive cats who feel the need to gorge their food quickly are more likely to eat spoiled food. Feed cats in separate closed rooms to reduce competition.

Try a slow feed bowl

Bowls with ridges or mazes built in force cats to eat more slowly. This gives the smell and taste of spoiled food more chance to deter them.

Buy smaller single-serve cans

Cats are more likely to finish smaller 3-4 oz cans in one sitting before bacteria multiply. Large cans stay fresher longer after opening when refrigerated promptly.

Avoid plastic food containers

Plastic absorbs food odors and bacteria making it harder for cats to detect old food. Use glass, ceramic or metal containers with tight lids.

Clean between feedings

Wash food bowls thoroughly to remove residue where bacteria can flourish until the next meal.

Check expiration dates

Canned food can look and smell fine but still be past safe consumption if old. Always check expiration dates and discard expired food.


Eating spoiled wet cat food raises the risks of vomiting, diarrhea, and other harmful stomach issues. But a healthy cat’s natural defenses, good hygiene practices, close monitoring of freshness, and care around feeding times can greatly reduce chances of illness. Being watchful for symptoms and quickly contacting a vet if concerned ensures the best outcome. While extra care is needed with wet food to avoid spoilage, the benefits of the added hydration and protein still make it an optimal part of feline nutrition when handled properly. With some common sense precautions, cat owners can safely feed wet food without worrying about the consequences of it going bad.

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