Hedrin Once Liquid 15 Minute Gel 60ml eliminates head lice and their eggs in adults and children aged 6 months and over. It works by physically smothering the lice and also contains Penetrol which helps the product to penetrate louse eggs in order to kill them. The gel can safely be used as often as required without lice developing resistance. Fast acting, pesticide free and completely odourless! Work in with fingers or comb and wait 15 minutes, simply then directly apply shampoo and rinse out.