Abstract: The invention relates to the isolation, characterization and expression of DNA fragments encoding sphingomyelinases D from three species of Loxosceles genus spiders, namely L. boneti, L reclusa and L. laeta, and the toxoids thereof. The invention also relates to the production of active sphingomyelinases D and the toxoids thereof using recombinant means and to the use of same as an immunogen for the production in vertebrates of antibodies that neutralise the corresponding venom and the respective fragments F(ab?)2. The invention further relates to the use of recombinant sphingomyelinases D as part of an antigen matrix which can be used in the immunopurification of antibodies and the fragments thereof or as part of any diagnostic device used to obtain clinical confirmation that the causal agent of poisoning in a patient is a spider of the Loxosceles genus.