Hedrin Once kills head lice and eggs fast in just 15 minutes and is suitable for adults and children 6 months plus. Hedrin Once Liquid Gel kills head lice and their eggs. It is not a chemical poison but works by physically smothering the lice. It also contains Penetrol which helps the product to penetrate louse eggs in order to kill them. Hedrin Once Liquid Gel has been shown to work with only one application but a further check should be carried out one week after application to make sure that no lice or eggs have managed to escape the coating. If any live lice are discovered then the treatment can be re-applied. The gel can be used as often as required without lice developing resistance. Contains dimeticone, which kills lice by coating them. Clinically proven to kill head lice and eggs in just one application. Allergy Certified. Pesticide free. Only 1 x 15 minute treatment.