Ducton® was an injectable immunostimulant prepared from a strain (S103) of the pathogenic gram-negative bacteria Neisseria perflava. The product was used to stimulate the immune system, via the effect of bacterial peptidoglycans. Once injected, the prepared bacterial fraction stimulated production of antibodies directed against the peptide moiety of the peptidoglycan subunits. Neisseria perflava is a bacterium of the upper respiratory tract, and a constant inhabitant of patients with infectious asthma. Pigmented Neisseria species (including N. perflava) are active sensitizers of the human broncho-pulmonary tract. Their allergenic activity is high. Here, the objective of the treatment with Ducton® was to stimulate the immunological defense against bacterial allergens. A hard medicine for a hard problem, this was the principle of the product, with the idea to stimulate the natural defense against the pathogen. Ducton® was a liquid product (in glass ampules), in general intramuscularly injected. It is no longer in use today.