Bulging Cans and Damaged Food Packaging: Warning Signs That Mean You Should Throw the Food Away

Is a bulging or dented can safe to eat? Learn which packaging defects may signal contamination, botulism, seal failure, or spoilage—and when to discard food.

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Canned food is valued for its long shelf life, convenience, and ability to remain safe without refrigeration. That reliability depends on one essential feature: an intact, airtight seal.

When a can becomes swollen, starts leaking, develops severe rust, or is deeply dented near a seam, the protective barrier may no longer be reliable. Gas may be building inside, microorganisms may have entered through damaged packaging, or the metal may have reacted with the food. Whatever the cause, a visibly bulging can is not something to open for a closer look.

The safest response is simple: do not open it, do not taste the food, and do not try to rescue it by cooking. Dispose of the container carefully.

Bulging cans receive the most attention, but they are not the only warning sign. Glass jars, plastic pouches, cartons, vacuum-sealed packages, and bottled foods can also show signs of seal failure or spoilage.

This guide explains which packaging defects are dangerous, how to distinguish a minor dent from a serious one, and what to do if a suspicious container has already been opened.

Is a Bulging Can Always Unsafe?

A swollen can should be treated as unsafe.

The FDA advises consumers never to purchase a can that looks swollen or bulging, because the swelling may indicate that dangerous bacteria are growing inside. The CDC also lists bulging, leaking, or swollen containers among the signs that home-canned or commercially packaged food may be contaminated.

A can may swell for several reasons:

• Microorganisms may produce gas as they grow.
• The food may react chemically with the metal.
• Excessive heat may increase pressure inside the container.
• The contents may have frozen and expanded.
• The can may have been overfilled or improperly processed.
• The seal or seam may have failed.

Some causes may be less dangerous than others, but a consumer cannot reliably determine the cause by looking at the outside. Opening the container to smell or taste the food is not a safe test.

If both ends of the can are rounded outward, one end springs out when the other is pressed, or the can no longer sits normally on a flat surface, discard it.

Why Botulism Is a Concern

Foodborne botulism is rare, but it is a medical emergency. It is caused by a toxin produced by Clostridium botulinum and certain related bacteria. The toxin attacks the nerves and can cause muscle paralysis, breathing difficulty, and death.

Improperly processed low-acid canned foods are a particular concern because the bacteria can produce toxin under certain low-oxygen conditions. Examples of low-acid foods include many vegetables, meats, poultry products, seafood, and mixed dishes.

However, a bulging container does not prove that botulinum toxin is present, and a normal-looking container does not prove that it is absent. The CDC emphasizes that the toxin responsible for botulism cannot be seen, smelled, or tasted. Even a small taste of contaminated food can be deadly.

That is why you should never:

• Taste food from a suspicious container
• Smell deeply inside a bulging can or jar
• Lick a spoon used to inspect the contents
• Feed questionable canned food to a pet
• Try to make visibly spoiled food safe by boiling it
• Donate damaged canned goods
• Open a swollen container merely to release the pressure

The rule “when in doubt, throw it out” is especially important for home-canned foods and damaged low-acid canned products.

Packaging Warning Signs You Should Never Ignore

Warning sign	Recommended action
Bulging or swollen can	Do not open; discard carefully
Leaking container	Discard
Deep dent on a seam	Discard
Sharp or severe dent	Discard
Hole or puncture	Discard
Extensive or deep rust	Discard
Loose or raised jar lid	Discard without tasting
Broken safety button or vacuum seal	Discard
Liquid or foam spurts out	Stop handling and discard carefully
Mold, discoloration, or bad odor	Do not taste; discard
Swollen pouch or carton	Discard
Package torn or separating at seams	Discard
Minor shallow dent away from seams	Inspect carefully; may be usable if otherwise intact

1. Bulging or Swollen Ends

The top and bottom of a metal can should normally appear flat or slightly indented, depending on the package design. An outward bulge, rounded end, or can that rocks because the bottom has expanded is abnormal.

Do not press aggressively on a swollen can. Pressure inside the container may cause leakage or spray when the seal fails.

Bulging can also occur in foil pouches, plastic trays, cartons, and vacuum-sealed packages. If a package that is normally flat appears inflated without a clear manufacturer explanation, do not consume the food.

2. Leaks, Wetness, or Sticky Residue

A leaking package no longer has a dependable barrier against contamination. Liquid escaping through a hole or broken seam means microorganisms may also have entered.

Sticky residue around a can or jar may come from a nearby spilled product, but it can also indicate a very small leak. Separate the container and inspect it without opening it.

Discard packages with:

• Wet seams
• Dried food around the lid
• Sticky tracks down the side
• Pinholes
• Unexplained stains on the label
• Food trapped around a jar rim
• A seal that visibly moves or leaks

Do not wash a leaking can and return it to the pantry.

3. Deep or Sharp Dents

Not every dent carries the same level of risk. A small, smooth, shallow dent located in the middle of a can may be a cosmetic defect if the container is not leaking, rusted, swollen, or damaged at a seam.

Deep dents are different. The USDA recommends discarding deeply dented cans. A deep dent may have a sharp point or be large enough to place a finger into. It can weaken the metal, create a microscopic hole, or damage the protective inner coating.

A dent is especially concerning when it affects:

• The top seam
• The bottom seam
• The vertical side seam
• The area where a pull tab or lid attaches
• More than one surface of the can

When evaluating a dent, do not rely solely on whether food is visibly leaking. A damaged seal may allow air and bacteria inside without producing an obvious drip.

4. Rust and Corrosion

Light surface rust that wipes off may not have penetrated the metal, but extensive rust, pitting, flaking, or rust concentrated along a seam is a reason to discard the can.

Never open a badly rusted can to check whether the food looks normal. Corrosion may create tiny holes or weaken the seam.

Rust often develops when canned goods are stored in:

• Damp basements
• Garages with changing temperatures
• Cabinets under leaking plumbing
• Areas exposed to condensation
• Outdoor sheds
• Floodwater
• Humid spaces near stoves or dishwashers

Canned food should be kept in a cool, clean, dry location.

5. Spurting Liquid, Foam, or Unusual Pressure

A small sound when opening some vacuum-sealed foods can be normal. Forceful spraying, unexpected foaming, or liquid spurting from a shelf-stable container is not.

If a suspicious container releases liquid or foam:

1. Do not taste the food.
2. Keep your face away from the opening.
3. Prevent children and pets from entering the area.
4. Avoid touching the food with bare hands.
5. Follow safe disposal and cleanup guidance.

The food may also be unusually cloudy, discolored, slimy, moldy, or foul-smelling. These are clear reasons for disposal, but their absence does not guarantee safety.

6. Abnormal Glass Jar Lids

A properly sealed commercial or home-canned jar should have an intact lid held firmly in place by its vacuum seal.

Warning signs include:

• A lid that is raised or bulging
• A center button that moves up and down
• Food leaking from beneath the lid
• A cracked jar
• A chipped sealing rim
• Dried food around the seal
• Bubbles rising through food that should be still
• Unusual cloudiness
• Mold beneath the lid
• A lid that comes off with almost no resistance

Do not retighten a loose lid and return the jar to storage. If a home-canned jar loses its seal shortly after processing, follow a tested home-canning procedure for timely reprocessing or refrigeration. If you do not know when the seal failed, discard the food.

7. Swollen Pouches, Cartons, and Plastic Packages

Packaging concerns are not limited to metal cans.

Shelf-stable drink cartons, retort pouches, plastic cups, meal trays, and vacuum packages should maintain their intended shape and seal. Throw them away if they are:

• Puffed or ballooned
• Leaking
• Punctured
• Torn
• Separating at a heat-sealed edge
• Crushed badly enough to damage the closure
• Contaminated around the opening
• Resealed, taped, or repaired

Some packaging is designed with a small amount of air inside, so compare it with an undamaged package of the same product when possible. An unexpected change from its original shape is the important warning sign.

What Should You Do With a Bulging Can?

For an unopened, swollen commercially canned product, avoid opening or puncturing it. Place it where children and animals cannot reach it while preparing it for disposal.

A practical approach is to:

1. Put on disposable gloves if the container is leaking.
2. Place the sealed container in a heavy plastic bag.
3. Close the bag securely.
4. Place it inside a second bag if leakage is possible.
5. Put it in a covered outdoor trash container.
6. Wash your hands thoroughly afterward.
7. Clean any surface the package touched.

Do not place a swollen can in regular recycling. Recycling programs generally require empty containers, and opening a suspicious can to empty it would create an unnecessary exposure risk.

If the product is under recall, follow the disposal or return instructions provided in the recall notice rather than improvising.

Special Precautions for Suspect Home-Canned Food

Home-canned food deserves additional caution because safety depends on using a scientifically tested recipe, the correct canning method, proper pressure or boiling time, jar size, acidity, and altitude adjustment.

Low-acid foods generally require pressure canning. Processing them in a boiling-water canner is not an acceptable substitute.

The National Center for Home Food Preservation recommends placing a still-sealed swollen can or suspect jar in a heavy garbage bag and disposing of it in a regular trash container.

Do not open a suspect home-canned jar to inspect, smell, or empty it. Do not pour the food into a garbage disposal, sink, compost pile, garden, or animal feeding area.

If you are uncertain whether the food was canned according to a current tested recipe, discard it—even if the lid is sealed and the food appears normal.

What If the Container Has Already Been Opened?

If you open a container and discover spurting liquid, foam, an abnormal odor, mold, or other spoilage:

• Do not taste the food.
• Do not touch your mouth or face.
• Keep other people and pets away.
• Wash exposed skin with soap and water.
• Avoid spreading the contents to additional surfaces.
• Follow public-health guidance for cleaning a suspected botulism spill.

For suspect home-canned food, cleanup may require a freshly prepared bleach solution and sufficient contact time. Because bleach concentrations vary, follow current guidance from the CDC or National Center for Home Food Preservation. Never mix bleach with ammonia, vinegar, acids, or other cleaners.

Porous items that cannot be cleaned safely may need to be discarded. Wash contaminated clothing separately and thoroughly clean reusable utensils only if public-health guidance indicates they can be safely decontaminated.

What If Someone Ate the Food?

Eating from a swollen container does not automatically mean a person will become ill, but potential botulism exposure must be taken seriously.

Symptoms can include:

• Double or blurred vision
• Drooping eyelids
• Slurred speech
• Difficulty swallowing
• Dry mouth
• Muscle weakness
• Difficulty breathing
• Nausea, vomiting, or abdominal symptoms in some cases

Botulism is a medical emergency. If someone develops possible symptoms after eating home-canned food or food from a suspicious package, seek emergency medical care immediately. Do not wait for symptoms to worsen.

Keep the remaining food and packaging away from people and pets unless emergency personnel or a health department tells you how to preserve it for testing. Do not carry a leaking container into a clinic or hospital without instructions.

How to Prevent Can and Package Damage at Home

Good storage reduces both spoilage risks and unnecessary waste.

• Store canned foods in a cool, dry cabinet.
• Keep them away from plumbing leaks and condensation.
• Avoid locations with extreme heat or freezing temperatures.
• Rotate older products to the front.
• Inspect packages before placing them in the pantry.
• Do not stack heavy items on flexible cartons or pouches.
• Avoid dropping cans.
• Clean spills promptly to prevent rust.
• Check stored foods periodically for swelling and leakage.
• Follow manufacturer instructions after opening.
• Never use home-canning methods from unverified social media posts.

When shopping, leave damaged products on the shelf and notify a store employee. Do not buy a swollen can because it is discounted.

Frequently Asked Questions

Can I cook food from a bulging can to make it safe?

No. A visibly swollen container should be discarded unopened. Cooking is not a reliable justification for handling or tasting food from damaged packaging.

Is a small dent in a can dangerous?

A shallow, smooth dent away from the seams may be cosmetic if the can is otherwise intact. Discard it if the dent is deep, sharp, leaking, rusted, swollen, or located on a seam.

Can I return a bulging can to the store?

Contact the retailer or manufacturer first. They may request the product code, photographs, or receipt. Do not transport a leaking or dangerously swollen container unless they provide safe instructions.

Does a bad smell prove botulism?

No. Botulinum toxin cannot be identified by smell, taste, or appearance. A bad odor means the product should be discarded, but a normal odor does not prove it is safe.

Can I feed questionable canned food to animals?

No. Pets, livestock, and wildlife may also become ill, and leaving contaminated food accessible can spread it around the environment.

Final Thoughts

A bulging can is a clear warning, not a challenge to investigate. Do not open it, taste it, smell it closely, or attempt to save the food through cooking. The same caution applies to leaking containers, deep seam dents, extensive rust, raised jar lids, and swollen pouches or cartons. Careful disposal costs far less than gambling with a serious foodborne illness. Have you ever found a swollen can, loose jar lid, or unexpectedly inflated package in your pantry? Share what you noticed and how you handled it in the comments so other readers can learn from your experience.