Some poisons are also toxins, which is any poison produced by animals, vegetables or bacterium, such as the bacterial proteins which cause tetanus and botulism. A distinction between the two terms is not always observed, even among scientists. The derivative forms toxic and poisonous are synonymous.ndeed, 2,4-D is not a poison, but classified as harmful (EU). Many substances regarded as poisons are toxic only indirectly, by toxication. An example is wood alcohol or methanol, which is not poisonous itself, but is chemically converted to toxic formaldehyde and formic acid in the liver.