Toxins are substances created by plants and animals that are poisonous to humans. Toxins also include some medicines that are helpful in small doses, but poisonous in large amounts.
Most toxins that cause problems in humans come from germs such as bacteria. For example, cholera is caused by a poisonous bacteria.
Other toxins that cause problems include metals, such as lead, and certain chemicals in the environment.
Kao LW, Rusyniak DE. Chronic poisoning, trace metals and others. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 22.
Kulig K. General approach to the poisoned patient. In: Marx JA, Hockberger RS, Walls RM, et al, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 8th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 147.