False. Foods that are improperly stored become what is known as a growth medium for microorganisms. These foods can be dangerous to humans and animals, and while they may cause an internal parasite to be able to grow, such as a tape worm, they are not in and of themselves parasites. Parasites are an organism that feeds off of, or is parasitic, and sustains life from another living organism. Such as a flea feeding off the blood of a dog or cat.