The invention relates to a composition for the detection of traces of human or animal blood. The aforementioned composition comprises a luminol compound, an oxidizing agent and a base which are diluted in a preferably aqueous solvent. Said composition is characterized in that: the luminol compound is present in a quantity providing a concentration of between 1 and 20 mmoles/l in the end composition, the oxidizing agent is hydrogen peroxide which is present at a concentration of between 25 and 100 mmoles/l in the end composition, the base is soda, NaOH, which is present at a concentration of between 25 mmoles/l and 500 mmoles/l in the end composition. The invention also relates a kit and a method for preparing said composition. Furthermore, the invention relates to a method of detecting and locating traces of human or animal blood.