Hedrin Liquid Gel is clinically proven to kill head lice and eggs. It is a thicker gel formulation which contains Penetrol to aid the penetration of the louse egg, making it fast acting to shorten treatment time. Hedrin Once works with just one application in just 15 minutes by physically smothering head lice and eggs. Always read the full instruction leaflet before you start. To begin, shake the bottle and apply the gel straight onto dry hair. Work the solution in with a comb or fingers covering the hair from root to tip and leave in for 15 minutes. Once complete, apply shampoo to dry hair before wetting and washing out. Suitable for up to 10 treatments.