A mycotoxin (from Greek μύκης (mykes, mukos) fungus and τοξικόν (toxikon) poison) is a toxic secondary metabolite produced by organisms of the fungi kingdom, commonly known as molds. The term 'mycotoxin' is usually reserved for the toxic chemical products produced by fungi that readily colonize crops.One mold species may produce many different mycotoxins, and the same mycotoxin may be produced by several species.ome of the health effects found in animals and humans include death, identifiable diseases or health problems, weakened immune systems without specificity to a toxin, and as allergens or irritants. Some mycotoxins are harmful to other micro-organisms such as other fungi or even bacteria; penicillin is one example.