Diatomaceous earth is a sediment composed of the fossilized skeletons of ancient aquatic microorganisms known as diatoms. These microscopic skeletons are composed of silicon dioxide, also known as silica, which is also the main chemical compound in sand.
Diatomaceous earth is useful in a variety of applications. It can be found in beverages, skin care products and even toothpaste. It is usually in the form of a fine grained dust, and while it can cause skin or respiratory irritation, it is not poisonous, according to the National Pesticide Information Center. One of the most common uses of diatomaceous earth is to eliminate insect pests, such as ants or cockroaches. Silica dehydrates insects, and the spiny portions of the microscopic skeletons in diatomaceous earth impale the exoskeletons of insects, which further speeds up this process.