Accidents evoked by venomous animals are common in tropical regions. In Brazil, envenomation evoked by snakes, spiders and scorpions are an important public health problem. Their venoms are composed of a great number of toxins, which are capable of acting on tissue and plasma components with consequent toxic and pharmacological effects. On the other hand, the diversity of venom composition makes them important source of toxins that can be employed as scientific tools. Here we describe the mechanisms of anti and pro-inflammatory properties of toxins of Bothrops and Crotalus genus snakes and Loxosceles and Phoneutria genus spider venoms. The emphasis was to summarise, both in vivo and in vitro, studies that focused on the action of phospholipases, metalloproteinases and sphingomyelinase D on vascular and cellular aspects of the process as well as the complex network of chemical mediators involved.