Toxins are a variety of substances produced by bacteria, fungi, plants, or animals, that have a harmful effect on humans (or other life forms). Many are typically encountered naturally via contaminated food sources and can cause characteristic clinical syndromes (e.g., botulism, paralytic shellfish poisoning, and neurotoxic shellfish poisoning). See Table 1 for an abbreviated comparison and Appendix H for a more detailed discussion on toxins. Snake, spider and scorpion envenomation are covered in two JTS envenomation CPGs.29,30