"Putrescine (sometimes spelled putrescin) is a foul-smelling [1] organic chemical compound NH2(CH2)4NH2 
(1,4-diaminobutane or butanediamine) that is related to cadaverine; both are produced by the breakdown of amino acids in living and dead organisms and both are toxic in large doses.[2][3] The two compounds 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. They are also found in semen and some microalgae, together with related molecules like spermine and spermidine."