The growth inhibitory effect of allicin vapour and allicin in solution to clinical isolates of lung pathogenic bacteria from the genera Pseudomonas, Streptococcus, and Staphylococcus, including multi-drug resistant (MDR) strains, was demonstrated. Allicin was synthesised (>98% pure) by oxidation of diallyl disulfide by H2O2 using formic acid as a catalyst.