Toxin

A toxin is a poisonous substance produced by living organisms that can cause harm to other organisms, including humans. In scientific usage, toxins are distinguished from toxicants, which are poisonous substances not produced by living systems. Toxins can be proteins or peptides, as well as small molecular compounds, and they range from highly specific enzymatic inhibitors to broad-spectrum cytotoxins.

Biological toxins originate from a variety of sources. Plants, animals, and microorganisms all produce toxins as defensive or predatory tools. Examples include botulinum and tetanus neurotoxins, ricin from castor beans, aflatoxins produced by certain fungi, and animal venoms such as those of snakes, spiders, and cone snails. Venoms are delivery systems that transport toxins through bites or stings.

Toxins act through diverse mechanisms, often interfering with cellular processes, membrane integrity, or signaling pathways. They may inhibit protein synthesis, disrupt ion channels, damage membranes, or activate immune responses. Their effects depend on dose, route of exposure (ingestion, inhalation, dermal contact, injection), and the organism’s susceptibility. The concept of LD50, the dose that kills 50% of a test population, is commonly used to compare relative toxicities.

Medical relevance is addressed in toxicology and emergency medicine. Management emphasizes decontamination when appropriate, symptomatic and supportive care, and, where available, specific antidotes or antitoxins. Detection and quantification of toxins rely on analytical assays, and public health frameworks monitor exposure risks from environmental, occupational, and consumer sources.

Commonly cited examples include botulinum toxin, a potent neurotoxin; tetrodotoxin, which blocks voltage-gated sodium channels; ricin, a ribosome-inactivating protein; and aflatoxins, hepatocarcinogenic fungal toxins.