Poisonous and Toxic

Poisonous (adjective) describes any substance, natural or manufactured, that is harmful or deadly to living cells, even in small quantities.

Toxic (adjective) refers to poison that is produced naturally by living things, but people often use ‘toxic’ to describe any substance that is harmful or not good for you e.g. ‘toxic fumes’. This is very common, especially in non-technical language.


  1. Comment by lori

    thx that was great!

  2. Comment by Ethan

    What about usage such as water toxicity?

  3. Comment by admin

    Interesting comment, Ethan. “Water toxicity” usually refers to the level of harmful substances (of any kind) in water. So water utility companies, for example, do water toxicity tests to make sure water is OK to drink. Why not water poisonousness tests? Maybe the word is just too long and awkward! It seems that the distinction between toxins and poisons is not maintained in longer words like ‘toxicity’ and ‘toxicology’ The alternative words, poisonousness and poisonology are rarely used.
    ‘Water toxicity’ is sometimes used erroneously to describe the harmful effects of drinking too much water. The correct term for this is ‘water intoxication’.

  4. Comment by Holman

    What is the difference between a toxin and a prion?

  5. Comment by admin

    The difference between a toxin and a prion:
    A toxin is a substance that poisons or irritates whereas a prion is a type of infectious agent. But unlike infectious viruses and bacteria, prions are not cellular organisms. Prions are proteins that normally perform a beneficial function in animal tissue; but they can become abnormally shaped, leading to illness. According to the US Food and Drug Administration – http://www.fda.gov/Food/FoodSafety/FoodborneIllness/FoodborneIllnessFoodbornePathogensNaturalToxins/BadBugBook/ucm071397.htm – abnormal prions can be infectious when consumed by other animals. Prions are thought to be absorbed into the body during digestion where they begin the process of changing their normal protein counterparts into abnormal proteins; however infectious prions from one species of animal have less of a potential of causing the abnormal shape in the normally shaped prion proteins of another species (the “species barrier”).

  6. Comment by Dave

    difference between toxic and noxious?

  7. Comment by admin

    Noxious means harmful or injurious – noxious substances, noxious weeds, a noxious idea

  8. Comment by Isaiah

    Dirrerence between corrosive and poison?

  9. Comment by admin

    Corrosives (corrosive substances) are immediately damaging to a surface that they contact, such as skin, eyes, lungs or throat. Poisons, on the other hand, usually enter the body through the skin or gut and have a harmful effect on your system. They usually require time to work. There are substances that are both corrosive and poisonous, and in non-technical language, people ofter refer to corrosives as “poisons”.

  10. Comment by Greggy

    So, a toxin is a substance created organically that has POTENTIAL to harm, that is to say,
    If a creature were to adapt to a previously harmful substance, it would still technically be a toxin, even if not identified as toxic to the individual,
    But in this case, everything organic is a toxin, because everything organic has potential, in some dose, to cause harm,
    Same with inorganic poisons,
    Sorry, guess my question is;
    Is there a system to determine what gets labeled as “harmful is small enough doses to be considered a toxic/poison”, or is it just nobody cares about obviously not very toxic/poisonous things like water etc.
    Also is there a system that differentiates toxin like venoms, which are not made to have immunities built to, and toxins like in Wormwood, which I’m guessing the plant or whoever made it was planning on creatures developing sort of immunities to to achieve the health benefits, or is the Wormwood toxicity actually meant to ward off predators?
    Herbs are really confusing me at this point, I’m having trouble understanding why they are so intensely awesome. Specifically in the context of human consumption. It’s crazy.

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