Botulism is a type of toxin that can attack your body with potentially fatal consequences. One way to tell if canned milk is infected with this toxin is the presence of swelling. Additionally, dented can of sweet or evaporated milk are thought to be potential vectors for this toxin. Make sure you always inspect the milk to ensure none of these factors are present. Apart from dents, botulism in condensed milk is also caused by milk that has gone far past its expiration date. Look for the characteristic swelling of the can when looking for signs of botulism.