Exotoxins are toxins shed by some bacterial cells into the surrounding environment. They can cause severe health problems locally or to other parts of the organism, where they are carried through the bloodstream.

Bacterial toxins are not freely liberated into the surrounding environment. The damaging components are only released when the cell disintegrates. The complex macromolecules (lipopolysaccharides) can then cross the barrier into the bloodstream, especially in animals exposed to various types of challenges, and cause or enhance health issues.

Mycotoxins are secondary metabolites produced by fungi. They too can cause severe health issues in animals, especially through the contamination of feedstuffs. This contamination is very common and often invisible to the naked eye.