Why must bulging cans of vegetables not be eaten?

Bulging cans of vegetables should never be consumed because they pose a serious health risk. While bulging is often caused by harmless chemical reactions between the metal container and acidic food contents, it can also indicate that the canning process was inadequate.1

If the heat treatment used during processing fails to destroy all bacteria spores, the environment inside a sealed can may allow Clostridium botulinum to survive and multiply. These bacteria can produce a deadly toxin that causes botulism, a severe and potentially fatal paralytic syndrome. Because it is impossible to distinguish between a harmless chemical reaction and the presence of dangerous pathogens without laboratory testing, you must prioritize your safety and discard any bulged cans immediately.12