The active ingredient in Licener is the natural Neem-extract, originating from the Neem tree. When applied according to the directions the extract covers, immobilises and suffocates lice causing them to die. It also penetrates tiny openings at the top of the eggs called aeropyles (breathing holes) blocking the oxygen flow which causes the carbon dioxide to build up and the nits suffocate and die. The Neem extract also breaks down the protective shell of the (eggs) nits. In this way Licener kills both the lice and nits in a single treatment.