Alkaloid ("Agonopterix alstroemeriana)." This moth feeds on its highly toxic and alkaloid-rich host plant poison hemlock ("Conium maculatum") during its larval stage. "A. asltroemeriana" may benefit twofold from the toxicity of the naturally-occurring alkaloids, both through the unpalatability of the species to predators and through the ability of "A. alstroemeriana" to recognize "Conium maculatum" as the correct location for oviposition. Medical use of alkaloid-containing plants has a long history, and, thus, when the first alkaloids were isolated in the 19th century, they immediately found application in clinical practice. Many alkaloids are still used in medicine, usually in the form of salts,
Poison drilling rigs). Plant-based contact irritants, such as that possessed by poison ivy or poison oak, are often classed as allergens rather than poisons; the effect of an allergen being not a poison as such, but to turn the body's natural defenses against itself. Poison can also enter the body through the teeth (in the controversial case of dental malpractice), faulty medical implants, or by injection (which is the basis of lethal injection in the context of capital punishment). In 2013, 3.3 million cases of unintentional human poisonings occurred. This resulted in 98,000 deaths worldwide, down from 120,000 deaths in 1990.