Nicotine and neonicotinoid insecticides are a class of compounds that are highly toxic to insects and less so to humans. They are especially effective at controlling undesirable pest insects to increase agricultural crop productivity. The specific actions of these chemicals exploit specific sensitivities within the neurologic systems of insects, resulting in knockdown, immobilization, and death in the target species. Depending on which molecule, mammalian physiology is either similarly sensitive to these chemicals (nicotine) or resistant to them (neonicotinoids). Toxic reactions to human exposure depend on dose, route, and duration of exposure. These agents are so potent and persistent in the exposed (treated) plants that beneficial, non-pest insect populations that come into contact with them are affected.