When a Canned Product Becomes Unsafe to Keep
A canned food must be removed from circulation — meaning taken off shelves in stores, pulled from your pantry, or destroyed — when it shows signs of botulism risk, physical damage that breaks the seal, or has been recalled by the manufacturer or a food safety authority. The most common reason is a swollen or bulging can, which signals that bacteria inside have produced gas. This is a sign of botulism, a serious foodborne illness, and the can should never be opened or tasted.
Other cans that must go are those with deep dents along the seam (the top or bottom edge), cracks, leaks, or rust that has eaten through the metal. If a can was stored in freezing temperatures and the contents expanded enough to crack the seal, it is no longer safe. Any can involved in a recall — announced by the FDA, the USDA, or the manufacturer — must be removed, even if it looks fine.
Key Takeaways
- A swollen or bulging can must always be discarded because it indicates bacterial gas production and possible botulism.
- Deep dents on the seam, leaks, cracks, or rust that penetrates the metal mean the seal is broken and the food is unsafe.
- Cans involved in a manufacturer or FDA recall must be removed from shelves and homes, regardless of appearance.
- Freezer damage that cracks the can or breaks the seal makes the contents unsafe, even if the can was sealed when frozen.
- Removing unsafe cans protects against botulism and other foodborne pathogens that grow in the anaerobic (oxygen-free) environment inside a sealed can.
Swollen or Bulging Cans and Botulism Risk
A swollen can is the clearest sign that a canned food is no longer safe. The swelling happens because bacteria — most dangerously Clostridium botulinum, which causes botulism — produce gas as they multiply inside the sealed, oxygen-free environment. This gas builds pressure and pushes the can outward.
Botulism is rare but serious: it can cause paralysis, difficulty breathing, and death if untreated. The toxin produced by the bacteria is one of the most potent poisons known. The danger is that botulism does not always change the smell, taste, or appearance of food, so you cannot tell by looking or smelling whether a can is contaminated. If a can is swollen, assume it is unsafe and throw it away without opening it.
Even a slightly swollen can should be discarded. Do not attempt to cook the food, taste it, or open it to inspect the contents. Dispose of it in a way that pets or children cannot access it, and wash your hands afterward.
Dents, Leaks, Cracks, and Rust That Break the Seal
Any damage that breaks the seal of a can allows bacteria and other microorganisms from the air or environment to enter. A deep dent along the seam — the crimped edge at the top or bottom of the can — is particularly dangerous because the seam is where the lid is sealed to the body. If the dent is deep enough to have created a crease or sharp fold, the seal is compromised.
Shallow dents on the flat sides of the can are generally safe if they do not affect the seam or create sharp edges. However, if you are uncertain whether a dent is deep enough to have broken the seal, err on the side of caution and discard the can.
Leaks are obvious: if liquid is seeping out, the seal is broken and the contents are unsafe. Cracks in the metal, even tiny ones, allow contamination. Rust that has eaten through the metal (called a pinhole or perforation) also breaks the seal. Surface rust — discoloration on the outside — does not necessarily mean the can is unsafe, but rust that has created a hole or is spreading rapidly should prompt you to discard it.
Freezer Damage and Temperature Extremes
Canned foods stored in a freezer can expand if the contents freeze. If the expansion is severe enough, it can crack the can or force the lid slightly open, breaking the seal. Once the seal is broken, the food is no longer protected from contamination.
If you find a can that was frozen and has a visible crack, dent from expansion, or any sign that the lid has lifted, remove it from circulation. The same applies to cans that have thawed after freezing — if the seal was compromised during the freeze-thaw cycle, bacteria can grow during thawing.
Canned foods are designed to be stored at room temperature or in a cool, dry place. Freezing is not recommended for canned goods, so if you have frozen cans, inspect them carefully before use.
Manufacturer and FDA Recalls
Food recalls are issued when a manufacturer discovers a safety problem — contamination, mislabeling, undeclared allergens, or other hazards — after a product has been sold. The FDA (Food and Drug Administration) and the USDA (U.S. Department of Agriculture) maintain public recall lists, and manufacturers are required to announce recalls through these agencies and through their own channels.
If a canned product is recalled, it must be removed from store shelves and from your home, even if the can looks and smells fine. Recalls can affect entire production batches or specific date codes. Check the recall notice to see whether your can is included — it will usually list the product name, brand, size, and the date code or "best by" date range affected.
You can search for recalls on the FDA website (fda.gov) or the USDA website (usda.gov). If you have a recalled product, do not open it. Return it to the store where you bought it, or dispose of it safely.
How to Safely Dispose of Unsafe Cans
Never open a can you suspect is unsafe. Do not taste it, smell it closely, or cook with it. Place the can in a sealed bag or container so that no one — including pets or children — can access it. If the can is swollen or leaking, you may want to place it in a separate bag to contain any spillage.
Dispose of the sealed bag in your regular trash. Some communities have hazardous waste programs, but canned food is not typically considered hazardous waste and can go in household garbage. If you are concerned about a specific situation — for example, a can that is actively leaking — contact your local waste management authority for guidance.
After handling a damaged or suspicious can, wash your hands thoroughly with soap and warm water.
Frequently Asked Questions
Is a can with a small dent on the side safe to use?
A shallow dent on the flat side of the can is usually safe if it has not created a crease or sharp fold and does not affect the seam. However, if the dent is deep, sharp-edged, or located on the seam (the crimped edge at the top or bottom), the seal may be broken and the can should be discarded.
What should I do if I accidentally opened a swollen can?
Do not taste or consume any of the food. Wash your hands and any utensils that touched the contents with hot soapy water. If you have eaten any of the food and develop symptoms like muscle weakness, difficulty swallowing, or blurred vision within hours or days, seek medical attention when ready and mention the swollen can.
Can I use a can that was frozen if it looks fine now?
If the can was frozen and has thawed, inspect it carefully for cracks, dents from expansion, or any sign that the lid has lifted. If the seal appears intact and there is no visible damage, it is likely safe. However, if there is any doubt, discard it rather than risk it.
Where can I learn about a product has been recalled?
The FDA maintains a searchable recall database at fda.gov, and the USDA has a separate recall page at usda.gov. You can search by product name, brand, or date code. Many manufacturers also send recall notices via email or post them on their websites.
Is surface rust on a can dangerous?
Surface rust — discoloration on the outside of the can — does not necessarily mean the food inside is unsafe, as long as the rust has not eaten through the metal. However, if rust is spreading, has created a hole, or is located on the seam, the can should be discarded.