Putrescine is a polyamine. Putrescine is related to cadaverine (another polyamine). Both are produced by the breakdown of amino acids in living and dead organisms and both are toxic in large doses. Putrescine and cadaverine are largely responsible for the foul odor of putrefying flesh, but also contribute to the odor of such processes as bad breath and bacterial vaginosis. Putrescine has been identified as a uremic toxin according to the European Uremic Toxin Working Group. It is also found in semen. Putrescine attacks s-adenosyl methionine and converts it to spermidine. Spermidine in turn attacks another s-adenosyl methionine and converts it to spermine. Putrescine is synthesized in small quantities by healthy living cells by the action of ornithine decarboxylase. The polyamines, of which putrescine is one of the simplest, appear to be growth factors necessary for cell division. Putrescine apparently has specific role in skin physiology and neuroprotection. Pharmacological interventions have demonstrated convincingly that a steady supply of polyamines is a prerequisite for cell proliferation to occur. Genetic engineering of polyamine metabolism in transgenic rodents has shown that polyamines play a role in spermatogenesis, skin physiology, promotion of tumorigenesis and organ hypertrophy as well as neuronal protection. Transgenic activation of polyamine catabolism not only profoundly disturbs polyamine homeostasis in most tissues, but also creates a complex phenotype affecting skin, female fertility, fat depots, pancreatic integrity and regenerative growth. Transgenic expression of ornithine decarboxylase antizyme has suggested that this unique protein may act as a general tumor suppressor. Homozygous deficiency of the key biosynthetic enzymes of the polyamines, ornithine and S-adenosylmethionine decarboxylase is not compatible with murine embryogenesis. Putrescine can be found in Citrobacter, Corynebacterium, Cronobacter and Enterobacter (https://onlinelibrary.wiley.com/doi/full/10.1111/1541-4337.12099).